Stations, bench and recovery

Each student station

Shared by one pair of students. The lab numbers refer to the students' labs page.

Students can use their own phones. The bench PC replaces the phone in every lab, with a desktop imager for writing images and the Amlogic USB boot tool for starting a board over USB, so students without an Android phone are never blocked. Final-project parts are extra and chosen by each pair.

Shared bench equipment

One set for every four to six stations.

Setting up the lab

• Pre-test every board. Boot each one from known-good boot media, check that Ethernet links and the I2C and SPI overlays apply, and label it with its station number.
• Choose one image for the term from the libre.computer catalogue, so the app and the desktop imager write the same image. Record its checksum and its default login, write two USB drives (Das Frite) or microSD cards (Solitude) per station, and keep the image file on the bench PCs so no lab waits on a download.
• Capture the power-up traces. Until published traces are on the materials page, probe the 5 V input, the rails and reset on one board per platform with a multi-channel oscilloscope, capture one power-up, and copy the capture to every bench PC for lab 2. A borrowed scope is enough: it is needed once.
• Prepare the build. Build the open boot chain for your platform with libretech-builder-simple on the bench PCs once per term, and test starting a board over USB with it, and with a changed memory clock, before Lab 3.
• Confirm kernel headers. The kernel-module part of the driver lab needs headers that match the chosen image; stage them with the course tools.
• Keep the boot files on the bench PCs. The published first stage and boot files from boot.libre.computer for starting a board over USB (lab 3 and recovery), and each board's firmware update image from the board firmware update images guide, for restoring SPI flash.
• Choose the section's stock distribution for lab 5. Pick one generic arm64 distribution from module 7's resources, and keep its image and published checksum on the bench PCs beside the course image. Record its default login, or how its first-boot setup creates one, for students.
• Stage the course tools. The lab network has no internet, so put the packages of libretech-wiring-tool and memtester that match the term image on the bench PCs, together with any of these the image lacks: dtc (lab 6), libgpiod with its C and Python bindings and its command-line tools, gpiodetect, gpioinfo, gpioset, gpioget and gpiomon (lab 6), i2c-tools (lab 7), a C and C++ compiler with make (labs 6 to 8, and the lab 8 kernel module), the Python spidev and smbus2 modules (labs 7 and 8) and the kernel headers matching the image (lab 8). On the bench PCs themselves, install the logic analyser's capture and decode software with its I2C, SPI and UART decoders (labs 6 to 8). Students install them at the end of lab 1.
• Keep the boards on a lab network. Use an isolated switch, with a small router on it serving DHCP and its uplink left unplugged (or a DHCP service on one bench PC), and connect each station's board and bench PC to it, so students can log in to the board and copy files to it from the bench PC. Put no board on the campus network without your school's approval.
• Give students a way to read. The labs open online references: the GPIO, layout and power viewers, the boards' schematics, part datasheets, the kernel's documentation and hub guides. Students read them on their own laptops or phones on the campus network, or give each bench PC a second, campus connection kept apart from the lab switch. Put the station parts' datasheets as files on every bench PC as well, and print each platform's 40-pin header map from the GPIO pinout for every station: the practical midterm allows datasheets, man pages and --help output, and the printed header map, and no other notes. Their bench page tells students where the datasheets and the header map are; tell them the midterm's allowed references yourself.
• Post the safety rules. Print the station sheet for your board and post it at every station; its rules match the students' bench page.
• Plan for phones. Ask the class who has an Android phone, and keep the desktop imager and the Amlogic USB boot tool on the bench PCs for everyone else.
• Run each lab first. A TA runs the week's lab on a spare station before the section meets.

When a board will not boot

Students work through their own list on their bench first: watch the console, swap and re-write the boot media, then hand the board to you. When a board reaches you:

Students never write a kit board's bootloader to its storage. Their own first-stage builds are loaded into SRAM over USB and write nothing, and the boot-breaking exercise in Lab 9 changes only spare boot media, after the TA has tested the recovery path.