This post continues my notes on Smart UPS 750, three years later, when it was time to replace the batteries (because they barely held for 13 minutes). It should have been simple, but if I wrote this lengthy post about it, there was clearly something going on.

Note that UPSes and their batteries is not my field. These are just my notes as I found my way through.

So for short, the main takeaways are these:

• Update the time of last battery replacement with the UPS’ front panel interface (somewhere under Configuration). This makes the UPS realize there are new batteries inside, which changes the way it calculates the estimated runtime.
• Two standard 12V / 7AH lead acid batteries can be used instead of APC’s original battery pack. But check that the terminals are 6mm wide.
• The displayed battery runtime is not reliable.

And now, the deep dive.

Replacing the batteries

The process for battery replacement with non-APC batteries is shown in this video, but it’s really not complicated. Yank off the front panel, then the pull down the metal panel behind the former, and pull out the batteries gently. Use the harness that connects the two existing batteries on the new ones, push them in and you’re done. Plus some packing tape to keep the two batteries together.

However the original batteries’ contact terminals are about 6mm wide, contrary to the ones on the battery I bought, which were considerably smaller. So even though there was no problem connecting the batteries, it wasn’t all that reassuring that the contacts were smaller. It seems like there are two standards for the terminal with, 6 mm being one of them.

This is a picture taken from above, showing the original pair of batteries I pulled out from the UPS (click to enlarge):

The blue thing in the middle contains a fuse, and the black connector at the top mates with the UPS.

But when I powered up the UPS, the expected runtime shown on the display was just 13 minutes, even though the charge level appeared as 100%. I was surprised to see a 100% charge level on batteries that were just installed, and even more disappointed with the expected runtime. Could it be that bad? Both APC’s runtime chart and my own simple energy calculation (see below) pointed at one hour at least with the load I had. And it didn’t improve after letting the UPS work for a few hours.

My first though was that I had been sold exceptionally junky batteries. But I bought them at a reputable electronics shop, and they carried a timestamp indicating they were fresh.

And then it occurred to me that I should tell the UPS that I had replaced batteries. So I went to the part in the UPS’ configuration menu for setting the month and year of the last battery change, and did that. And to my surprise, the runtime was adjusted to 1hr 12 minutes right away. There a few posts out there (this, for example) on how to “reset the battery constant” manually. It seems like this relates to the same thing.

Cute, I thought. But is that figure correct? So I let the UPS run on battery for a while. The estimated runtime went down in pace with the wall clock, but then suddenly, after 23 minutes, it took the power down.

So I reconnected the UPS back to power, and let the battery charge until it reached 100% again. At which point it reported:

$ apcaccess
APC      : 001,027,0652
DATE     : 2021-08-29 20:21:36 +0300
HOSTNAME : ruhe
VERSION  : 3.14.14 (31 May 2016) debian
UPSNAME  : ruhe
CABLE    : USB Cable
DRIVER   : USB UPS Driver
UPSMODE  : Stand Alone
STARTTIME: 2021-08-29 18:30:15 +0300
MODEL    : Smart-UPS 750
STATUS   : ONLINE
BCHARGE  : 100.0 Percent
TIMELEFT : 23.0 Minutes
MBATTCHG : 5 Percent
MINTIMEL : 3 Minutes
MAXTIME  : 300 Seconds
ALARMDEL : 30 Seconds
BATTV    : 26.6 Volts
NUMXFERS : 0
TONBATT  : 0 Seconds
CUMONBATT: 0 Seconds
XOFFBATT : N/A
STATFLAG : 0x05000008
MANDATE  : 2018-05-22
SERIALNO : AS1821351109
NOMBATTV : 24.0 Volts
FIRMWARE : UPS 09.3 / ID=18
END APC  : 2021-08-29 20:22:01 +0300

Smart UPS or what? If the battery died after 23 minutes last time, how much has it left when fully charged? Let me think… 23 minutes!

And yet, that sounds way too short for a new battery. More than 24 hours later, the same runtime estimation remained, going up and down a minute or so occasionally. So that’s that.

It could be correct, however. The way to find out is to try again after a month or so. For that, there’s battery calibration. Which for my UPS means “let the battery drain and measure its way down until it’s empty”. Haven’t tried that yet, but it seems more or less like unplugging power from the UPS. Note that the load will lose power at the end of this process. So the computer needs to be taken down safely, and then held in a state where a power failure won’t hurt (e.g. stuck in some boot menu). This way, it remains as an electrical load, but nothing bad happens when the power goes down.

Battery calibration is launched from the front panel menu as well.

Why calibration makes sense requires some deep diving into lead acid battery theory. Which is where this post goes next. Once again, lead acid batteries is really not my expertise. For a concise technical background, I recommend reading Power Sonic’s Technical Manual.

A 7AH battery doesn’t really give 7AH

The amount of charge (and energy) that a lead-acid battery supplies until it’s discharged depends dramatically on the discharging current. The capacity printed on the battery is given for a 20-hours discharge, or using the jargon, 0.05C. That “C” is 7 taken from the 7AH figure, so 7AH are obtained if the discharge current is 0.35A. For larger currents, expect much less energy out of the battery.

For example, my specific case: The load is 70W (at 142VA) according to the UPS itself. I’ll assume that the low power factor thing can be ignored, i.e. that the fact that the VA figure is twice the consumed power makes no difference. This low power factor is natural to switching power supplies, as they draw more current when the voltage is low, so their behavior is far from a plain resistor (unless specifically compensated to mitigate this effect). I’ll also assume that the UPS is 100% efficient on its voltage conversion, which is complete rubbish, but for the heck of it.

So for two 12V batteries in series it goes 70W/24V =~ 2.9A, which is about 0.4C (2.9 / 7 =~ 0.4). A ballpark figure can be taken from Figure 4 in Power Sonic’s Technical Manual, showing that the voltage starts to drop after about an hour, and reaches the critical value somewhere after an hour and a half. Note that I have different batteries.

Also from Table 2 of the same Manual, we have that the actual capacity of a 7AH battery, when drained with a 4.34A current, is 4.34AH (one hour). The current is higher than 2.9A, but given that the UPS isn’t really 100% efficient, it’s likely that the real discharge current is closer to 4A than to 2.9A. So that explains why the UPS said 1:12 hours when I updated the battery replacement date.

Now, it could be that different batteries behave differently on higher currents. I really don’t know. I couldn’t find data on my “Bulls Power” batteries. So maybe they could meet the 7AH specification for a 20-hours discharge, and then perform really poorly with higher, real-life currents. I have no idea.

Not directly related, but anyhow: The power consumption goes above double (165W, 217VA) when compiling a Linux kernel with 12 processes. The power factor improved considerably, in line with Corsair’s promise to attain power level of unity at full capacity (which is 850W, a long way to go).

Knowing the battery’s charge level

How does one estimate how much energy a lead-acid battery has? The answer is unpleasant, yet simple: There is really no way to measure it from the battery electronically. After reading quite some material on the subject, that became evident to me: There are plenty of papers describing exotic algorithms for estimating a battery’s health and charge level, and their abundance and variety proves that there’s really no way to tell, except for draining it.

Actually, there is one way that is considered reliable, which is measuring the open circuit voltage (OCV) after the battery has been disconnected for a while (some say a few hours, battery manufacturers typically require 24 hours). Letting the battery rest allows it to reach a chemical equilibrium, at which point the voltage reflects its charge level. This is surely true for a fresh battery.

As for batteries with some history, the picture is less clear, and I haven’t managed to figure out if the OCV voltages remain the same, and if the voltage vs. charge percentage relate to the original charge capacity, or the one that is available after the battery is worn out.

For example, Power Sonic claims that the OVC goes from 1.94V/cell to 2.16V/cell for 0% to 100% charge respectively. As a 12-volt battery has 6 cells, this corresponds to 11.64V to 12.96V. These figures are quite similar to those presented by another manufacturer.

But what does 100% charge mean? 7AH or as much as is left when the battery has worked for some time? My anecdotal measurement of the batteries I took out from the UPS was 12.99V after letting them rest. In other words, they presented a OCV voltage corresponding to 100% charge, even though they had much less than 7AH.

So how does a UPS estimate the remaining runtime? Well, the simple way is to let the battery run out once, and there you have a number. Clearly, Smart UPS uses this method.

Are there any alternatives? In theory, the UPS could let the battery rest for 24 hours, and measure its OCV. This is possible, because most of the time the UPS doesn’t need the battery. But even my anecdotal measurement shows that a 100% charge-like reading doesn’t mean much.

For other types of batteries (Li-ion in particular), measuring the current on the battery, in and out (Coulomb Counting), gives an idea on how much charge it contains. This doesn’t work with lead acid batteries, because the recommended way to maintain a standby battery, is to continuously float charge it. That means holding a constant voltage (say, 2.25V per cell, that is 13.5V for a 12V battery, or 27V on a battery pair, as in SmartUPS 750).

As this voltage is higher than the OCV at rest, this causes a small trickle current (said to be about 0.001C), which compensates for the battery’s self discharge. Even if it overcharges the battery slightly, the gases that are released are recycled internally in a sealed battery, so there’s no damage.

Hence the recommended strategy for charging a lead-acid battery is to charge it quickly as long as its voltage / current pair indicates that it’s far from being fully charged, and then apply a constant, known and safe voltage. This allows it to charge completely slowly, and then maintain the charge without any risk for overcharging. Odds are that this is what the UPS does.

But makes Coulomb Counting impossible: During the float charge phase (that is, virtually all the time) the current may and may not actually charge the battery.

Why recalibrate

It’s not clear what my Smart 750 UPS did with the batteries when recharging after they were completely empty. Even if did Coulomb Counting, it has no way to tell how efficient the battery will perform during discharge, while draining a current that is much higher than 0.05C.

I’m not even 100% sure that it did charge the battery fully in any of the cases. Even though lead-acid batteries have a pretty known charging voltage graph, which indicates when the battery is about to become full, the UPS might have played safe, and went for a float charge early. Maybe it doesn’t fast-charge a battery more than it has knowingly discharged it. If that’s the case, the remaining charge is acquired slowly by float charging.

As the UPS has no way to know whether the charging current is just a float charge or if the battery actually gains energy, it won’t update the estimated runtime.

So it’s possible that the UPS actually filled the battery properly to begin with, or that it did that during float charge phase. Or the batteries installed may be pure junk. This way or another, a battery calibration (or just let it run on battery until it dies out) a while later is the definite answer, as it covers the float charge possibility.

After quite a while of working perfectly well, the mini HDMI2AV module I have (in the picture above, mentioned in this post) started producing an unstable picture, and in the end a completely garbled one. It took some time to nail down this specific component in the foodchain, because there was also an HDMI splitter involved.

The problem, as it turned out, was that this module takes voltage from the HDMI plug, if such is available, instead of the dedicated power plug. In my specific setup, it seems like there was some voltage was available, but not enough to drive the device — because the HDMI plug was connected to the HDMI splitter. I suppose some internal power supply switch went into some not-here-not-there kind of situation, and eventually got some permanent damage. The other HDMI2AV unit I have didn’t work either in the same conditions, but probably didn’t reach the point of permanent damage (so it’s working right now).

On an HDMI connector, Pin 18 is +5V, minimum 55 mA, intended originally to feed the monitor with voltage even if it’s shut off, so its DDC (EDID) information can be obtained. Some devices (e.g. cheap HDMI splitters and HDMI to AV converters) might use this voltage instead of the supplied external voltage in some cases.

Not all cables conduct this pin. It’s therefore advisable to check the cable before working with it, when the setup is more than just a direct connection. It’s not easy, even with a multimeter. Pushing a thin wire into the tiny holes at the front may give contact with the relevant pin, but this isn’t bulletproof. Possibly try with an HDMI/DVI adapter (pin 14 on a DVI connector is +5V). Or test with a device that is known to rely on this voltage (e.g. this HDMI2AV module).

The solution in my case was to replace the HDMI2AV module and all cables with such that don’t let the +5V wire through. In particular, it seems like the cable to the TV set (via HDMI) that went to the HDMI splitter (which connects to the HDMI2AV module on its other output) was the issue.

So the procedure is simple (cited from manual, page 7, “Pairing”):

1. Turn the ignition on.
2. Make sure the Bluetooth feature of your phone is turned on.
3. Start the pairing procedure on your mobile phone.
4. When prompted for a passkey, enter 1234 on your mobile phone

The crucial hint is that nothing is expected to happen in the “Phone” any setup menu, as shown in many video tutorials.

So on an Android phone, open Settings > Bluetooth and make it search for devices. Once it finds it, enter the 1234 passcode (it’s was actually suggested, that and 0000. So it was 1234). Don’t expect anything to happen on the car radio’s side nor the dashboard display until the phone is paired.

I managed to pair two phones (the manual says there are up to five allowed).

$ xrandr --verbose

which outputs a lot of information about the display, in particular the EDID information obtained from the monitor. Among others, it’s a detailed listing of the video modes that the monitor is willing to accept. These modes are usually the standard VESA graphics modes, but there’s no guarantee that they are. But in reality, they are probably all industry standard, in particular those repeating themselves in the different dumps.

Also in reality, most monitors will display anything thrown at them, as long as it makes sense (or not) even if the graphics mode doesn’t appear on the list. After all, no monitor manufacturer wants the screen to be black when the competitor’s monitor shows as image.

So here are two such dumps. The first one is from my Lenovo Yoga 2 13″ (non-pro) laptop connected to a Dell P2415Q monitor, so the first set of data relates to the laptop’s own screen, and the second set to the much better external monitor (which goes up to UHDTV at 60 fps).

The second set is just my desktop, which is connected to a Samsung 23″ LS23ELDKF (a.k.a LED XL2370HD) monitor.

So the Laptop first:

Screen 0: minimum 320 x 200, current 5760 x 2160, maximum 32767 x 32767
eDP1 connected primary 1920x1080+0+0 (0x47) normal (normal left inverted right x axis y axis) 293mm x 165mm
 Identifier: 0x43
 Timestamp:  3827058
 Subpixel:   unknown
 Gamma:      1.0:1.0:1.0
 Brightness: 1.0
 Clones:   
 CRTC:       0
 CRTCs:      0 1 2
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:
 EDID:
 00ffffffffffff0006af2d2000000000
 00160104901d117802bc05a2554c9a25
 0e505400000001010101010101010101
 0101010101011d3680a070381e403020
 8e0025a5100000181d36800872386640
 30208e0025a510000018000000fe0041
 554f0a202020202020202020000000fe
 004231333348414e30322e30200a0043
 BACKLIGHT: 94
 range: (0, 94)
 Backlight: 94
 range: (0, 94)
 scaling mode: Full aspect
 supported: None, Full, Center, Full aspect
 Broadcast RGB: Automatic
 supported: Automatic, Full, Limited 16:235
 audio: auto
 supported: force-dvi, off, auto, on
 1920x1080 (0x47)  138.5MHz -HSync -VSync *current +preferred
 h: width  1920 start 1968 end 2000 total 2080 skew    0 clock   66.6KHz
 v: height 1080 start 1088 end 1102 total 1110           clock   60.0Hz
 1920x1080 (0xae)  138.5MHz -HSync -VSync
 h: width  1920 start 1968 end 2000 total 2440 skew    0 clock   56.8KHz
 v: height 1080 start 1088 end 1102 total 1182           clock   48.0Hz
 1920x1080 (0xaf)  138.5MHz +HSync -VSync
 h: width  1920 start 1968 end 2000 total 2080 skew    0 clock   66.6KHz
 v: height 1080 start 1083 end 1088 total 1111           clock   59.9Hz
 1680x1050 (0xb0)  146.2MHz -HSync +VSync
 h: width  1680 start 1784 end 1960 total 2240 skew    0 clock   65.3KHz
 v: height 1050 start 1053 end 1059 total 1089           clock   60.0Hz
 1680x1050 (0xb1)  119.0MHz +HSync -VSync
 h: width  1680 start 1728 end 1760 total 1840 skew    0 clock   64.7KHz
 v: height 1050 start 1053 end 1059 total 1080           clock   59.9Hz
 1600x1024 (0xb2)  103.1MHz +HSync +VSync
 h: width  1600 start 1600 end 1656 total 1664 skew    0 clock   62.0KHz
 v: height 1024 start 1024 end 1029 total 1030           clock   60.2Hz
 1400x1050 (0xb3)  122.0MHz +HSync +VSync
 h: width  1400 start 1488 end 1640 total 1880 skew    0 clock   64.9KHz
 v: height 1050 start 1052 end 1064 total 1082           clock   60.0Hz
 1280x1024 (0xb4)  108.0MHz +HSync +VSync
 h: width  1280 start 1328 end 1440 total 1688 skew    0 clock   64.0KHz
 v: height 1024 start 1025 end 1028 total 1066           clock   60.0Hz
 1440x900 (0xb5)  106.5MHz -HSync +VSync
 h: width  1440 start 1520 end 1672 total 1904 skew    0 clock   55.9KHz
 v: height  900 start  903 end  909 total  934           clock   59.9Hz
 1280x960 (0xb6)  108.0MHz +HSync +VSync
 h: width  1280 start 1376 end 1488 total 1800 skew    0 clock   60.0KHz
 v: height  960 start  961 end  964 total 1000           clock   60.0Hz
 1360x768 (0xb7)   84.8MHz -HSync +VSync
 h: width  1360 start 1432 end 1568 total 1776 skew    0 clock   47.7KHz
 v: height  768 start  771 end  781 total  798           clock   59.8Hz
 1360x768 (0xb8)   72.0MHz +HSync -VSync
 h: width  1360 start 1408 end 1440 total 1520 skew    0 clock   47.4KHz
 v: height  768 start  771 end  781 total  790           clock   60.0Hz
 1152x864 (0xb9)   81.6MHz -HSync +VSync
 h: width  1152 start 1216 end 1336 total 1520 skew    0 clock   53.7KHz
 v: height  864 start  865 end  868 total  895           clock   60.0Hz
 1024x768 (0xba)   65.0MHz -HSync -VSync
 h: width  1024 start 1048 end 1184 total 1344 skew    0 clock   48.4KHz
 v: height  768 start  771 end  777 total  806           clock   60.0Hz
 800x600 (0xbb)   40.0MHz +HSync +VSync
 h: width   800 start  840 end  968 total 1056 skew    0 clock   37.9KHz
 v: height  600 start  601 end  605 total  628           clock   60.3Hz
 800x600 (0xbc)   36.0MHz +HSync +VSync
 h: width   800 start  824 end  896 total 1024 skew    0 clock   35.2KHz
 v: height  600 start  601 end  603 total  625           clock   56.2Hz
 640x480 (0xbd)   25.2MHz -HSync -VSync
 h: width   640 start  656 end  752 total  800 skew    0 clock   31.5KHz
 v: height  480 start  490 end  492 total  525           clock   59.9Hz
HDMI1 connected 3840x2160+1920+0 (0xe3) normal (normal left inverted right x axis y axis) 527mm x 296mm
 Identifier: 0x44
 Timestamp:  3827058
 Subpixel:   unknown
 Gamma:      1.0:1.0:1.0
 Brightness: 1.0
 Clones:   
 CRTC:       1
 CRTCs:      0 1 2
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:
 EDID:
 00ffffffffffff0010acc0a04c553630
 2d18010380351e78eae245a8554da326
 0b5054a54b00714f8180a9c0a940d1c0
 e10001010101a36600a0f0701f803020
 35000f282100001a000000ff00503250
 43323442343036554c0a000000fc0044
 454c4c205032343135510a20000000fd
 001d4c1e8c1e000a2020202020200196
 02032af15390050402071601141f1213
 2720212203061115230907076d030c00
 1000303c200060030201023a80187138
 2d40582c25000f282100001f011d8018
 711c1620582c25000f282100009e0474
 0030f2705a80b0588a000f282100001e
 565e00a0a0a02950302035000f282100
 001a00000000000000000000000000f9
 Broadcast RGB: Automatic
 supported: Automatic, Full, Limited 16:235
 audio: auto
 supported: force-dvi, off, auto, on
 3840x2160 (0xe3)  262.8MHz +HSync -VSync *current +preferred
 h: width  3840 start 3888 end 3920 total 4000 skew    0 clock   65.7KHz
 v: height 2160 start 2163 end 2168 total 2191           clock   30.0Hz
 3840x2160 (0xe4)  297.0MHz +HSync +VSync
 h: width  3840 start 4016 end 4104 total 4400 skew    0 clock   67.5KHz
 v: height 2160 start 2168 end 2178 total 2250           clock   30.0Hz
 3840x2160 (0xe5)  297.0MHz +HSync +VSync
 h: width  3840 start 4896 end 4984 total 5280 skew    0 clock   56.2KHz
 v: height 2160 start 2168 end 2178 total 2250           clock   25.0Hz
 3840x2160 (0xe6)  297.0MHz +HSync +VSync
 h: width  3840 start 5116 end 5204 total 5500 skew    0 clock   54.0KHz
 v: height 2160 start 2168 end 2178 total 2250           clock   24.0Hz
 3840x2160 (0xe7)  296.7MHz +HSync +VSync
 h: width  3840 start 4016 end 4104 total 4400 skew    0 clock   67.4KHz
 v: height 2160 start 2168 end 2178 total 2250           clock   30.0Hz
 3840x2160 (0xe8)  296.7MHz +HSync +VSync
 h: width  3840 start 5116 end 5204 total 5500 skew    0 clock   53.9KHz
 v: height 2160 start 2168 end 2178 total 2250           clock   24.0Hz
 2560x1440 (0xe9)  241.5MHz +HSync -VSync
 h: width  2560 start 2608 end 2640 total 2720 skew    0 clock   88.8KHz
 v: height 1440 start 1443 end 1448 total 1481           clock   60.0Hz
 2048x1280 (0xea)  221.3MHz -HSync +VSync
 h: width  2048 start 2192 end 2416 total 2784 skew    0 clock   79.5KHz
 v: height 1280 start 1281 end 1284 total 1325           clock   60.0Hz
 1920x1080 (0xeb)  148.5MHz +HSync +VSync
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.5KHz
 v: height 1080 start 1082 end 1087 total 1125           clock   60.0Hz
 1920x1080 (0xec)  148.5MHz +HSync +VSync
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.5KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   60.0Hz
 1920x1080 (0xed)  148.5MHz +HSync +VSync
 h: width  1920 start 2448 end 2492 total 2640 skew    0 clock   56.2KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   50.0Hz
 1920x1080 (0xee)  148.4MHz +HSync +VSync
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.4KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   59.9Hz
 1920x1080i (0xef)   74.2MHz +HSync +VSync Interlace
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   33.8KHz
 v: height 1080 start 1084 end 1094 total 1125           clock   60.1Hz
 1920x1080i (0xf0)   74.2MHz +HSync +VSync Interlace
 h: width  1920 start 2448 end 2492 total 2640 skew    0 clock   28.1KHz
 v: height 1080 start 1084 end 1094 total 1125           clock   50.0Hz
 1920x1080 (0xf1)   74.2MHz +HSync +VSync
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   33.8KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   30.0Hz
 1920x1080 (0xf2)   74.2MHz +HSync +VSync
 h: width  1920 start 2448 end 2492 total 2640 skew    0 clock   28.1KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   25.0Hz
 1920x1080 (0xf3)   74.2MHz +HSync +VSync
 h: width  1920 start 2558 end 2602 total 2750 skew    0 clock   27.0KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   24.0Hz
 1920x1080i (0xf4)   74.2MHz +HSync +VSync Interlace
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   33.7KHz
 v: height 1080 start 1084 end 1094 total 1125           clock   60.0Hz
 1920x1080 (0xf5)   74.2MHz +HSync +VSync
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   33.7KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   30.0Hz
 1920x1080 (0xf6)   74.2MHz +HSync +VSync
 h: width  1920 start 2558 end 2602 total 2750 skew    0 clock   27.0KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   24.0Hz
 1920x1080i (0xf7)   72.0MHz +HSync -VSync Interlace
 h: width  1920 start 1952 end 2120 total 2304 skew    0 clock   31.2KHz
 v: height 1080 start 1126 end 1136 total 1250           clock   50.0Hz
 1600x1200 (0xf8)  162.0MHz +HSync +VSync
 h: width  1600 start 1664 end 1856 total 2160 skew    0 clock   75.0KHz
 v: height 1200 start 1201 end 1204 total 1250           clock   60.0Hz
 1600x900 (0xf9)  119.0MHz -HSync +VSync
 h: width  1600 start 1696 end 1864 total 2128 skew    0 clock   55.9KHz
 v: height  900 start  901 end  904 total  932           clock   60.0Hz
 1280x1024 (0xfa)  135.0MHz +HSync +VSync
 h: width  1280 start 1296 end 1440 total 1688 skew    0 clock   80.0KHz
 v: height 1024 start 1025 end 1028 total 1066           clock   75.0Hz
 1280x1024 (0xb4)  108.0MHz +HSync +VSync
 h: width  1280 start 1328 end 1440 total 1688 skew    0 clock   64.0KHz
 v: height 1024 start 1025 end 1028 total 1066           clock   60.0Hz
 1152x864 (0xfb)  108.0MHz +HSync +VSync
 h: width  1152 start 1216 end 1344 total 1600 skew    0 clock   67.5KHz
 v: height  864 start  865 end  868 total  900           clock   75.0Hz
 1280x720 (0xfc)   74.2MHz +HSync +VSync
 h: width  1280 start 1390 end 1430 total 1650 skew    0 clock   45.0KHz
 v: height  720 start  725 end  730 total  750           clock   60.0Hz
 1280x720 (0xfd)   74.2MHz +HSync +VSync
 h: width  1280 start 1720 end 1760 total 1980 skew    0 clock   37.5KHz
 v: height  720 start  725 end  730 total  750           clock   50.0Hz
 1280x720 (0xfe)   74.2MHz +HSync +VSync
 h: width  1280 start 1390 end 1430 total 1650 skew    0 clock   45.0KHz
 v: height  720 start  725 end  730 total  750           clock   59.9Hz
 1440x576i (0xff)   27.0MHz -HSync -VSync Interlace
 h: width  1440 start 1464 end 1590 total 1728 skew    0 clock   15.6KHz
 v: height  576 start  580 end  586 total  625           clock   50.1Hz
 1024x768 (0x100)   78.8MHz +HSync +VSync
 h: width  1024 start 1040 end 1136 total 1312 skew    0 clock   60.1KHz
 v: height  768 start  769 end  772 total  800           clock   75.1Hz
 1024x768 (0xba)   65.0MHz -HSync -VSync
 h: width  1024 start 1048 end 1184 total 1344 skew    0 clock   48.4KHz
 v: height  768 start  771 end  777 total  806           clock   60.0Hz
 1440x480i (0x101)   27.0MHz -HSync -VSync Interlace
 h: width  1440 start 1478 end 1602 total 1716 skew    0 clock   15.8KHz
 v: height  480 start  488 end  494 total  525           clock   60.1Hz
 1440x480i (0x102)   27.0MHz -HSync -VSync Interlace
 h: width  1440 start 1478 end 1602 total 1716 skew    0 clock   15.7KHz
 v: height  480 start  488 end  494 total  525           clock   60.1Hz
 800x600 (0x103)   49.5MHz +HSync +VSync
 h: width   800 start  816 end  896 total 1056 skew    0 clock   46.9KHz
 v: height  600 start  601 end  604 total  625           clock   75.0Hz
 800x600 (0xbb)   40.0MHz +HSync +VSync
 h: width   800 start  840 end  968 total 1056 skew    0 clock   37.9KHz
 v: height  600 start  601 end  605 total  628           clock   60.3Hz
 720x576 (0x104)   27.0MHz -HSync -VSync
 h: width   720 start  732 end  796 total  864 skew    0 clock   31.2KHz
 v: height  576 start  581 end  586 total  625           clock   50.0Hz
 720x480 (0x105)   27.0MHz -HSync -VSync
 h: width   720 start  736 end  798 total  858 skew    0 clock   31.5KHz
 v: height  480 start  489 end  495 total  525           clock   60.0Hz
 720x480 (0x106)   27.0MHz -HSync -VSync
 h: width   720 start  736 end  798 total  858 skew    0 clock   31.5KHz
 v: height  480 start  489 end  495 total  525           clock   59.9Hz
 640x480 (0x107)   31.5MHz -HSync -VSync
 h: width   640 start  656 end  720 total  840 skew    0 clock   37.5KHz
 v: height  480 start  481 end  484 total  500           clock   75.0Hz
 640x480 (0x108)   25.2MHz -HSync -VSync
 h: width   640 start  656 end  752 total  800 skew    0 clock   31.5KHz
 v: height  480 start  490 end  492 total  525           clock   60.0Hz
 640x480 (0xbd)   25.2MHz -HSync -VSync
 h: width   640 start  656 end  752 total  800 skew    0 clock   31.5KHz
 v: height  480 start  490 end  492 total  525           clock   59.9Hz
 720x400 (0x109)   28.3MHz -HSync +VSync
 h: width   720 start  738 end  846 total  900 skew    0 clock   31.5KHz
 v: height  400 start  412 end  414 total  449           clock   70.1Hz
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
 Identifier: 0x45
 Timestamp:  3827058
 Subpixel:   no subpixels
 Clones:   
 CRTCs:      3
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:

And the Samsung monitor:

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
VGA-0 disconnected (normal left inverted right x axis y axis)
 Identifier: 0x51
 Timestamp:  110079
 Subpixel:   no subpixels
 Clones:   
 CRTCs:      0 1
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:
 load detection: 1 (0x00000001)    range:  (0,1)
HDMI-0 disconnected (normal left inverted right x axis y axis)
 Identifier: 0x52
 Timestamp:  110079
 Subpixel:   horizontal rgb
 Clones:   
 CRTCs:      0 1
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:
 audio:    off
 supported: off          on           auto       
 underscan vborder: 0 (0x00000000)    range:  (0,128)
 underscan hborder: 0 (0x00000000)    range:  (0,128)
 underscan:    off
 supported: off          on           auto       
 coherent: 1 (0x00000001)    range:  (0,1)
DVI-0 connected 1920x1080+0+0 (0x54) normal (normal left inverted right x axis y axis) 510mm x 287mm
 Identifier: 0x53
 Timestamp:  110079
 Subpixel:   horizontal rgb
 Clones:   
 CRTC:       0
 CRTCs:      0 1
 Transform:  1.000000 0.000000 0.000000
 0.000000 1.000000 0.000000
 0.000000 0.000000 1.000000
 filter:
 EDID:
 00ffffffffffff004c2d2a0733323037
 0e14010380331d782a81f1a357539f27
 0a5054bfef8081009500b3008140714f
 8180a940950f023a801871382d40582c
 4500fe1f1100001e000000fd00384b1e
 5111000a202020202020000000fc0053
 4d584c3233373048440a2020000000ff
 004831414b3530303030300a202000a1
 load detection: 1 (0x00000001)    range:  (0,1)
 audio:    off
 supported: off          on           auto       
 underscan vborder: 0 (0x00000000)    range:  (0,128)
 underscan hborder: 0 (0x00000000)    range:  (0,128)
 underscan:    off
 supported: off          on           auto       
 coherent: 1 (0x00000001)    range:  (0,1)
 1920x1080 (0x54)  148.5MHz +HSync +VSync *current +preferred
 h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.5KHz
 v: height 1080 start 1084 end 1089 total 1125           clock   60.0Hz
 1600x1200 (0x55)  162.0MHz +HSync +VSync
 h: width  1600 start 1664 end 1856 total 2160 skew    0 clock   75.0KHz
 v: height 1200 start 1201 end 1204 total 1250           clock   60.0Hz
 1680x1050 (0x56)  119.0MHz +HSync -VSync
 h: width  1680 start 1728 end 1760 total 1840 skew    0 clock   64.7KHz
 v: height 1050 start 1053 end 1059 total 1080           clock   59.9Hz
 1280x1024 (0x57)  135.0MHz +HSync +VSync
 h: width  1280 start 1296 end 1440 total 1688 skew    0 clock   80.0KHz
 v: height 1024 start 1025 end 1028 total 1066           clock   75.0Hz
 1280x1024 (0x58)  108.0MHz +HSync +VSync
 h: width  1280 start 1328 end 1440 total 1688 skew    0 clock   64.0KHz
 v: height 1024 start 1025 end 1028 total 1066           clock   60.0Hz
 1440x900 (0x59)  136.8MHz -HSync +VSync
 h: width  1440 start 1536 end 1688 total 1936 skew    0 clock   70.6KHz
 v: height  900 start  903 end  909 total  942           clock   75.0Hz
 1440x900 (0x5a)   88.8MHz +HSync -VSync
 h: width  1440 start 1488 end 1520 total 1600 skew    0 clock   55.5KHz
 v: height  900 start  903 end  909 total  926           clock   59.9Hz
 1280x960 (0x5b)  108.0MHz +HSync +VSync
 h: width  1280 start 1376 end 1488 total 1800 skew    0 clock   60.0KHz
 v: height  960 start  961 end  964 total 1000           clock   60.0Hz
 1280x800 (0x5c)   71.0MHz +HSync -VSync
 h: width  1280 start 1328 end 1360 total 1440 skew    0 clock   49.3KHz
 v: height  800 start  803 end  809 total  823           clock   59.9Hz
 1152x864 (0x5d)  108.0MHz +HSync +VSync
 h: width  1152 start 1216 end 1344 total 1600 skew    0 clock   67.5KHz
 v: height  864 start  865 end  868 total  900           clock   75.0Hz
 1024x768 (0x5e)   78.8MHz +HSync +VSync
 h: width  1024 start 1040 end 1136 total 1312 skew    0 clock   60.1KHz
 v: height  768 start  769 end  772 total  800           clock   75.1Hz
 1024x768 (0x5f)   75.0MHz -HSync -VSync
 h: width  1024 start 1048 end 1184 total 1328 skew    0 clock   56.5KHz
 v: height  768 start  771 end  777 total  806           clock   70.1Hz
 1024x768 (0x60)   65.0MHz -HSync -VSync
 h: width  1024 start 1048 end 1184 total 1344 skew    0 clock   48.4KHz
 v: height  768 start  771 end  777 total  806           clock   60.0Hz
 832x624 (0x61)   57.3MHz -HSync -VSync
 h: width   832 start  864 end  928 total 1152 skew    0 clock   49.7KHz
 v: height  624 start  625 end  628 total  667           clock   74.6Hz
 800x600 (0x62)   50.0MHz +HSync +VSync
 h: width   800 start  856 end  976 total 1040 skew    0 clock   48.1KHz
 v: height  600 start  637 end  643 total  666           clock   72.2Hz
 800x600 (0x63)   49.5MHz +HSync +VSync
 h: width   800 start  816 end  896 total 1056 skew    0 clock   46.9KHz
 v: height  600 start  601 end  604 total  625           clock   75.0Hz
 800x600 (0x64)   40.0MHz +HSync +VSync
 h: width   800 start  840 end  968 total 1056 skew    0 clock   37.9KHz
 v: height  600 start  601 end  605 total  628           clock   60.3Hz
 800x600 (0x65)   36.0MHz +HSync +VSync
 h: width   800 start  824 end  896 total 1024 skew    0 clock   35.2KHz
 v: height  600 start  601 end  603 total  625           clock   56.2Hz
 640x480 (0x66)   31.5MHz -HSync -VSync
 h: width   640 start  656 end  720 total  840 skew    0 clock   37.5KHz
 v: height  480 start  481 end  484 total  500           clock   75.0Hz
 640x480 (0x67)   31.5MHz -HSync -VSync
 h: width   640 start  664 end  704 total  832 skew    0 clock   37.9KHz
 v: height  480 start  489 end  491 total  520           clock   72.8Hz
 640x480 (0x68)   30.2MHz -HSync -VSync
 h: width   640 start  704 end  768 total  864 skew    0 clock   35.0KHz
 v: height  480 start  483 end  486 total  525           clock   66.7Hz
 640x480 (0x69)   25.2MHz -HSync -VSync
 h: width   640 start  656 end  752 total  800 skew    0 clock   31.5KHz
 v: height  480 start  490 end  492 total  525           clock   60.0Hz
 720x400 (0x6a)   28.3MHz -HSync +VSync
 h: width   720 start  738 end  846 total  900 skew    0 clock   31.5KHz
 v: height  400 start  412 end  414 total  449           clock   70.1H

Just in case this is helpful to anyone…

But hey, this never happened in the past! Asking a round a bit, I was advised to check if the fan is OK. Maybe the thermal paste went dry.

Opening the case and looking, I noticed that the heatsink was full with dust. More precisely, a lot of dust was stuck between the heatsink’s grill blades, obstructing the air flow. No air flow, no cooling. So I unsnapped the fan off the heatsink, took a vacuum cleaner, and removed all dust.

And my PC is like new now! The temperature goes from 30.0°C to no more than 44.0°C when I run that kernel compilation test (watching the temperature with “watch sensors” at shell prompt).

It was that simple.

Note to self: Vacuum the CPU’s heatsink every now and then.

And here’s what it looks like after two years, during which the computer has been on continuously (click on images to enlarge):

And this is with the fan taken off. One can clearly see that the layer of dust disrupts the air flow.

A minute with the vacuum cleaner, and we have

Snap the fan back in place, and the computer is ready to go!

I can’t say I’m disappointed, because I didn’t really expect things to work as specified on a $10 camera.

Even though the manual promises 70 minutes of recording time, I got 48 minutes in reality before the camera stopped itself (the memory card wasn’t full, it was the battery that ran out).

Note that a MicroSD card needs to be purchased separately, which will cost significantly relative to the camera’s price (some $8 in a store, possibly $4 on EBay for a Sandisk card). The largest file I managed to obtain with a 48 minutes recording was 1.7 GB, so a 2 GB card is probably large enough.

LED colors

It looks like the LED colors were changed since the manual was written. The blue LED is the power LED, indicating that the device is on. The red LED says something is happening.

Optics and image quality

The image is a 720x480, apparently progressive (non-interlaced) rolling shutter with a noise level that resembles web cameras from the late 90′s. The measured opening angle on the frame’s width was as narrow as 25 degrees which, I suppose is about 80mm focal length on a 35mm-equivalent scale. In other words, this is with a slight touch of a tele lens.

The camera was announced having an 80 degrees view angle by its EBay seller, which turned out to be wrong. The narrow angle is a problem for most relevant applications, since it the desired subject gets off-frame easily. It’s also the reason for the shaky footage this camera emits. I’m not even sure about using this as a helmet camera.

With a $1 Jelly Lens, the angle of view rises to 40 degrees, which is around 50mm focal length (on a 35mm scale). In other words, the extra lens is some x0.6 (not very impressive, but what did I expect from a $1 lens?) and it gives the camera a “normal” focal length. The sticky adhesive on the jelly lens held the very small piece of plastic firmly in place. I don’t know how well this would work on a helmet cam, though. Did I say $1?

I should mention, that for a cellular phone with an already pretty wide angle, this Jelly Lens actually achieves an impressive wide angle (and green visible borders). So it’s a very good deal, given its price…

Another lens tried out was the AGPtek “180 Degrees” lens for cellular phones for some $5. It is often announced as x0.28, but it’s not. My measurement was 53 degrees, which is about 36 mm focal length (on a 35mm scale), so the lens did in fact x0.45. Better than the Jelly Lens, but by far not as good as expected. It does have a slight roundoff in the corners like a fish-eye lens at 53 degrees view angle, which gives the illusion that it’s wider than it actually is.

Charging

Connect the camera to a computer via USB, so it gets power. The blue LED goes on, and the red LED starts blinking. According to the user’s manual, a green LED should be blinking, but it looks like the color was changed to red. The user’s manual also says that the LED should stop blinking when the battery is charged, but that didn’t happen even after an overnight charging. It just went on blinking (red). According to the seller at EBay, the charging time should be 3 hours. Go figure.

Note that the MicroSD is mounted on the computer due to the USB connection.

Accessing the MicroSD card

Well, simply connect to the computer (as in for charging). The following (or similar) will appear at the log:

Jan 31 17:54:27 myhost kernel: hub 1-2:1.0: unable to enumerate USB device on port 2
Jan 31 17:54:29 myhost kernel: usb 1-2.2: new high speed USB device using ehci_hcd and address 62
Jan 31 17:54:29 myhost kernel: usb 1-2.2: New USB device found, idVendor=04d6, idProduct=e101
Jan 31 17:54:29 myhost kernel: usb 1-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Jan 31 17:54:29 myhost kernel: usb 1-2.2: Product: usbdisk  
Jan 31 17:54:29 myhost kernel: usb 1-2.2: Manufacturer: anyka    
Jan 31 17:54:29 myhost kernel: usb 1-2.2: SerialNumber: 942954944
Jan 31 17:54:29 myhost kernel: scsi102 : usb-storage 1-2.2:1.0
Jan 31 17:54:30 myhost kernel: scsi 102:0:0:0: Direct-Access     anyka    MMC Disk         1.00 PQ: 0 ANSI: 2
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: Attached scsi generic sg4 type 0
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] 3858560 512-byte logical blocks: (1.97 GB/1.83 GiB)
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] Write Protect is off
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] Assuming drive cache: write through
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] Assuming drive cache: write through
Jan 31 17:54:30 myhost kernel: sdd:
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] Assuming drive cache: write through
Jan 31 17:54:30 myhost kernel: sd 102:0:0:0: [sdd] Attached SCSI removable disk

This is just like connecting a disk-on-key, and so is the access to the content.

Using as a webcam

This is useful for getting an idea of the image quality, and immediate feedback for aiming the camera properly.

With the camera connected via USB (and hence the MicroSD card mounted), unmount the volume (“Safely Remove Drive” or something) and press the camera’s Power button for three seconds or so. The red LED will stop blinking, and the blue remains steadily on. The following lines in the log indicate the transformation into a web cam:

Jan 31 17:55:20 myhost kernel: usb 1-2.2: USB disconnect, address 62
Jan 31 17:55:21 myhost gnome-keyring-daemon[28416]: removing removable location: /media/New flash
Jan 31 17:55:21 myhost gnome-keyring-daemon[28416]: no volume registered at: /media/New flash
Jan 31 17:55:21 myhost gnome-keyring-daemon[3139]: removing removable location: /media/New flash
Jan 31 17:55:21 myhost gnome-keyring-daemon[3139]: no volume registered at: /media/New flash
Jan 31 17:55:23 myhost kernel: usb 1-2.2: new high speed USB device using ehci_hcd and address 63
Jan 31 17:55:23 myhost kernel: usb 1-2.2: New USB device found, idVendor=04d6, idProduct=e102
Jan 31 17:55:23 myhost kernel: usb 1-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Jan 31 17:55:23 myhost kernel: usb 1-2.2: Product: UVC..
Jan 31 17:55:23 myhost kernel: usb 1-2.2: Manufacturer: ANYKA
Jan 31 17:55:23 myhost kernel: usb 1-2.2: SerialNumber: 12345
Jan 31 17:55:23 myhost kernel: uvcvideo: Found UVC 1.00 device UVC.. (04d6:e102)
Jan 31 17:55:23 myhost kernel: uvcvideo: UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround.
Jan 31 17:55:23 myhost kernel: input: UVC.. as /devices/pci0000:00/0000:00:1a.7/usb1/1-2/1-2.2/1-2.2:1.0/input/input13

The last row indicates the generation of /dev/video0:

$ ls -l /dev/video0
crw-rw----+ 1 root video 81, 0 2013-01-31 17:55 /dev/video0

It’s important to start doing something with the webcam soon, or the camera goes into sleep mode. Running Cheese Webcam Booth (2.28.1) shows an immediate image. No configuration should be necessary (it should find /dev/video0 automatically).

Using as a stand-alone camera

According to the manual, the camera has two modes: Normal recording and audio-triggered. I haven’t tried the audio-triggered mode, and neither do I want to. To switch from one mode to another, there’s the “Mode” button. Which I’m not touching.

Needless to say, a MicroSD card must be inserted for this to work.

To start, make sure that the device is disconnected from the computer and off (no LED is on). Press the Power button for a second, wait a few seconds. Only the blue LED should lit steadily.

To start and stop recording, press the button on the camera’s short edge (next to the record/stop symbols). The red LED will blink at 0.5 Hz during recording.

If the “Mode” button is pressed, the red LED will blink at 2-3 Hz to indicate audio-triggered recording. Turning the camera off and on is the best way to make sure the camera is at a known state.

Playback

The video files are put in the “VIDEO” subdirectory. A typical playback session with mplayer looks like this:

$ mplayer "/media/New Flash/VIDEO/2012-9-21 18-26-54.AVI"
MPlayer SVN-r31628-4.4.4 (C) 2000-2010 MPlayer Team
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing /media/New Flash/VIDEO/2012-9-21 18-26-54.AVI.
AVI file format detected.
[aviheader] Video stream found, -vid 0
[aviheader] Audio stream found, -aid 1
VIDEO:  [MJPG]  720x480  24bpp  30.000 fps  2449.9 kbps (299.1 kbyte/s)
Clip info:
 Software: ankarec
Failed to open VDPAU backend libvdpau_nvidia.so: cannot open shared object file: No such file or directory
[vdpau] Error when calling vdp_device_create_x11: 1
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffmjpeg] vfm: ffmpeg (FFmpeg MJPEG)
==========================================================================
==========================================================================
Opening audio decoder: [pcm] Uncompressed PCM audio decoder
AUDIO: 8000 Hz, 1 ch, s16le, 128.0 kbit/100.00% (ratio: 16000->16000)
Selected audio codec: [pcm] afm: pcm (Uncompressed PCM)
==========================================================================
AO: [pulse] 8000Hz 1ch s16le (2 bytes per sample)
Starting playback...
Movie-Aspect is undefined - no prescaling applied.
VO: [xv] 720x480 => 720x480 Planar YV12
A:   3.0 V:   3.0 A-V:  0.001 ct:  0.002  92/ 92  5%  0%  0.1% 0 0

The video format is MJPEG 720x480 (not sure about the aspect ratio) with uncompressed 16 bit per sample mono sound, at 8 kHz sample rate. The file name represents the time at which recording began.

A small timestamp appears at the lower right of the recorded image.

Setting the time

This is somewhat confusing. The way to set the time, is to create a file called time.txt in the card’s root directory. To make things a bit complicated, the camera creates a file called TIME.TXT in the same place, with a timestamp sample (or something). Editing this file will do nothing. It’s a new file that needs to be created with something like

$ vi "/media/New Flash/time.txt"

It looks like the file appears from nowhere, with a sample timestamp (2012-09-21 17:08:56) set. Update it to something like

2013-01-31 19:45:00

or write it from scratch if nothing appears. Write and quit vi. Unmount the volume, unplug the camera, and turn it off. The camera will update the time to the file’s content when it starts up the next time.

There’s a null-character in the end in the sample timestamp. It can be omitted or left. Doesn’t matter.

Conclusion

Pretty much expected, it’s a piece of junk with poor documentation. Otherwise, it wouldn’t go for $10. But it’s good for putting in places where it has a good chance to get lost or destroyed, and hopefully get some cool footage when put on a helmet or something like that.

Everything was OK until it failed to start. Or more precisely, it started, and then restarted itself. Like this:

And again. And again. It turned out that a defective MicroSD flash card caused it to go crazy. So I replaced the card, and everything looked fine again. But then it had a horrible relapse: It went back to this restarting pattern again, but this time it didn’t help to take out the MicroSD card. What turned out to be really bad, was that it was impossible to connect it to a computer through USB for backup, because it would restart all the time.

It wasn’t a power supply thing. I learned that from the fact, that when the phone was started without a SIM, it asked me whether it should start the phone even so. And it didn’t restart as long as I didn’t press any button on that question.

So it was clear that the phone did something that went wrong a few seconds after being powered on. So the trick was to prevent it from getting on with its booting process, but still allow a USB connection.

Connecting the USB cord while in any of the pre-start menus turned out useless (Use without SIM? Exit from Flight mode?). So I looked a bit at the codes.

What did eventually work, was to use the *#06# code, which is used to check IMEI. The phone showed me the serial number and didn’t restart, and when I plugged in the USB cord, I got the usual menu allowing me to choose mode. From there on it was a lot of playing around, trying and retrying until I finally recovered my phone list.

This also made it possible to reprogram the handset with Nokia’s Phoenix software, which didn’t work otherwise. Neither did the Green-*-3 three finger salute for a deep reset nor the infamous *#7370# code for the same purpose. These two never did anything, even when the phone appeared to be sane.

I should point out, that it’s possible that this trick may have solved a very specific issue on my own phone’s internal messup, and still, I thought it was best to have it written down for rainy days.

ionice -c 3 -p 18898

And you have your computer back. “-c 3″ means class 3, which is idle class. In other words, take the disk when nobody else asks for it.

I love it. More here.

CONFIG STEPPING = "2";

to the UCF file. It must have been one of those moments where I believed that the tools do what is best for me.

It wasn’t long before the mapper told me it’s rewarding me with some autocalibration logic for the DCM. Sounded pretty OK. Some logic that will get the DCM back on its feet if the clock stops and returns. Not that I have any such plans. As a matter of fact, I’ve made sure that the DCM will get a reset after any possible messing with the DCM’s clock input.

Both the mapping warning and the docs mention that it’s possible to disable the autocalibration feature in order to save some logic. They never mentioned that the logic can kill the DCM.

And then one of the DCMs started losing lock. I had changed several other things at the same time, so it wasn’t easy to track down why. But it looked so weird: The DCM’s lock flag would go high, and then go down again. The timescale was tens of milliseconds, which is way beyond the response times  for a DCM.

My first thought was that it must have something to do with the clock’s signal quality. Maybe some crosstalk. The clock was around 200 MHz. But then I decided to look a bit closer on what this autocalibration was about.

That led me to Answer Record #21435, which was pretty explicit about the reset:

When the input clock returns, the user must manually assert the DCM reset for at least 200 ms to resume proper DCM functionality.

200 ms? So there is was. I did mess with the input clock, but then I sent a brief reset signal to the DCM to get it back to normal. It worked in the past. Not with the extra logic. So all I needed to do, was to add

defparam   thedcm.DCM_AUTOCALIBRATION = “FALSE”;

(in the Verilog definition of the DCM) and the problem (which shouldn’t have occured in the first place) was solved.

To make things slightly more annoying, I also had to upgrade the old “DCM” primitives to “DCM_BASE”, because when the “DCM” primitives are upgraded automatically to DCM_ADV’s (by XST),  the DCM_AUTOCALIBRATION parameter set to the default, which is “TRUE”. The same parameter simply doesn’t exist for the backward-compatible “DCM” primitive.

Note to self: Remember to disable the autocalibration on all DCMs from now on.

Tektronix 515A Oscilloscope

I got it when I was 13. Yes, some of us play with strange toys. I had a lot of fun moments with it, but the truth is that even if it worked, it’s not much of use, now that I’ve betrayed it with a young and colorful one.

Mechanically, this old scope is in good shape (it’s the one in the picture above). Electronically, it does turn on, but there is no beam. The panel lamps behave as expected, so I suppose that with some love and care, it can be fixed without major surgery.

The scope was manufactured in 1957. Naturally, it’s based upon vacuum tubes, which gives it the same nostalgic feel as an old radio.

There is no point in myself keeping it, but my sentiments won’t let me throw it in the dustbin. So I’m ready to give it away to a museum or serious collector. My basic condition, is that whoever wants it, will have to pay for the shipping. And if you’re serious about this kind of gear, you surely know that this “portable scope” weights 20 kg.

In case you’re interested, please drop me a note. My email address can be found at my website.

June 2019 update: Nah, I’ll keep it. If it’s been with me this long, it was probably meant to stay with me.