I also wanted to install OpenBSD onto a RaspberryPi 3 - unlike most RaspberryPi installs where a sdcard image is flashed and boots up - OpenBSD requires following the full installation procedure on the console. Sure you could hook up it up to HDMI and a USB keyboard, but what’s the fun in that? So I took the oppurtunity to do both.
Following the Hackernoon post, and using the RPI GPIO documentation, I soldered some lead pins onto the CHIPs
RXD breakout at the top, made some basic GPIO wires and hooked it all up. Using the
5V has the added benefit of powering the RaspberryPi from the CHIP battery, which in makes both of them portable.
To connect via serial console, first release
/dev/ttyS0 from systemd,
sudo systemctl stop serial-getty@ttyS0
The OpenBSD console uses a baud rate of
115100 and transmission of eight bits per byte
cs8. Connecting requires
sudo, even if your
chip user is in the
tty group due to some udev/systemd permissions wonkiness.
sudo screen /dev/ttyS0 115200,cs8
The serial console works well, although occasionally there is missing data, but after remembering how to use the OpenBSD disk partitioner - OpenBSD 6.8 was running on a RaspberryPi 3. Once the installation is complete, if DHCP was setup during install, connecting to it over ssh is trivial and no longer requires the serial console.
While as much fun as this is, it’s not nearly as useful as it could have been years ago when troubleshooting misbehaving Sun Netra or Sun Fire systems. For now though it’s a good hack, useful in the right circumstances, and just looks cool.