Simple GPIO on Zybo using command-line on Linux

Running Xillinux on the Zybo board, this is how I toggled a GPIO pin from a plain one-liner bash script in Linux. The same technique can be used for other Zynq-7000 boards (Zedboard in particular) to easily control GPIO pins. First, I looked up which GPIO pin it is. The pin assignments can be found [...]

Booting Vivado / EDK mixed FSBL on Zynq-7000

Background This is yet another war story about making the FSBL boot on a Zynq processor. I had prepared an FSBL for a certain target using SDK 14.6, and then someone needed it in a Vivado package, using the SDK attached to Vivado 2014.1. In a perfect world, I would have exported the system’s configuration [...]

Executing user-space programs from a different Linux distro

While trying to use executables from one ARM-based distribution to another, it failed to run, even before trying to load any libraries. The ARM architectures were compatible (armhf in both cases) so it wasn’t like I was trying to run an Intel binary on an ARM. I could always cross-compile from sources, but copying binaries [...]

“Unsupported machine ID” after upgrading Linux kernel or U-boot

Unlike how I usually treat software tools I work with, my attitude towards U-boot is “if it works, never mind how and why”. Trying to understand the gory details of U-boot has never been very rewarding. Things work or break more or less randomly, depending on which git revision is checked out. Someone sent a [...]

Linux kernel platform device food chain example

Since the device tree is the new way to set up hardware devices on embedded platforms, I hoped that I could avoid the “platform” API for picking which driver is going to take control over what. But it looks like the /arch/arm disaster is here to stay for a while, so I need to at [...]

Cache coherency on i.MX25 running Linux

What this blob is all about Running some home-cooked SDMA scripts on Freescale’s Linux 2.6.28 kernel on an i.MX25 processor, I’m puzzled by the fact, that cache flushing with dma_map_single(…, DMA_TO_DEVICE) doesn’t hurt, but nothing happens if the calls are removed. On the other hand, attempting to remove cache invalidation calls, as in dma_map_single(…, DMA_FROM_DEVICE) [...]

stmmaceth: NetworkManager fails to bring up a wired Ethernet NIC

The problem In short: Running linux 3.8.0 on Altera’s Cyclone V SoC, NetworkManager doesn’t bring up the Ethernet port. It also makes false accusations such as Jan 1 00:00:17 localhost NetworkManager[1206]: <info> (eth0): driver ‘stmmaceth’ does not support carrier detection. and later on also says Jan 1 00:00:17 localhost NetworkManager[1206]: <warn> (eth0): couldn’t get carrier [...]

Cyclone V SoC: Two masters on a bus errs on ID signal width

While working on Xillinux‘ port to Altera (the SocKit board, actually), I needed to connect two AXI masters: One for the VGA adapter, and one for the Xillybus IP core. Unlike Zynq, Altera’s HPS offers only one AXI slave port, so it’s up to Qsys to generate arbitration logic, implemented in the logic fabric, to [...]

Setting up a cross compiler: Buildroot notes

Just a quick summary on how to compile my own cross-compiler in 20 minutes. Download from Buildroot’s home page Run “make xconfig”. The configuration is stored in .config Possibly set BR2_JLEVEL=8 for parallel compilation(even though 0 should just do it right according to the number of processors present) Pick little Endian ARM Cortex-9 for Xillinux [...]

DHCP changing the IP address suddenly on embedded systems

The problem It first seemed extremely odd: The IP address of my embedded Linux machine changed suddenly after a few hours, breaking the ssh connection I had up, and messing up the NFS mount. The problem turned out to be the lack of a hardware clock (RTC) on the board + clock being updated with [...]