Teaching materials · Print one per station
Station pin-out and safety sheet
Pick the section's board with the platform switch, then print this page and post it at each station. Students' own copy of the rules is on their bench page.
Das Frite (AML-S805X-AC-V2): serial console
On the 40-pin header. Terminal: 115200 baud, 8 data bits, no parity, 1 stop bit.
| Header pin | Board signal | USB-to-UART adapter (3.3 V) |
|---|---|---|
| Pin 3 | Board receives | Adapter transmit |
| Pin 5 | Board transmits | Adapter receive |
| Pin 6 | Ground | Adapter ground |
| — | — | Adapter power pin: never connected |
Das Frite: power, boot media and controls
| Item | At this station |
|---|---|
| Power | 5 V over USB Type-C, from a supply rated 2 A |
| Boot firmware | UEFI bootloader in the 16 MB SPI NOR flash |
| OS boot media | USB flash drive in the USB Type-A port (no card slot); a spare drive holds a spare image |
| 40-pin header | 3.3 V logic. Every pin's functions: Das Frite GPIO pinout |
| Boot select switch | Changes which boot source the boot ROM tries first; the schematic's boot page shows how. Leave it in its normal position except during lab 3 |
| USB boot button | Hold it at power-on to put the board in USB boot mode, for starting it over USB from the phone or bench PC |
Solitude (AML-S905D3-CC): serial console
On the board's own 3-pin UART header, not the 40-pin header. Terminal: 115200 baud, 8 data bits, no parity, 1 stop bit.
| UART header pin | Board signal | USB-to-UART adapter (3.3 V) |
|---|---|---|
| Pin 1 | Ground | Adapter ground |
| Pin 2 | Board transmits | Adapter receive |
| Pin 3 | Board receives | Adapter transmit |
| — | — | Adapter power pin: never connected |
Solitude: power, boot media and controls
| Item | At this station |
|---|---|
| Power | 5 V over USB Type-C, from a supply rated 3 A |
| Boot firmware | UEFI bootloader in the 16 MB SPI NOR flash |
| OS boot media | microSD card in the card slot; a spare card holds a spare image |
| 40-pin header | 3.3 V logic. Every pin's functions: Solitude GPIO pinout |
| Boot select switch | Changes which boot source the boot ROM tries first; the schematic's boot page shows how. Leave it in its normal position except during lab 3 |
| USB boot button | Hold it at power-on to put the board in USB boot mode, for starting it over USB from the phone or bench PC |
Safety rules
| Rule | Why |
|---|---|
| The header is 3.3 V. Never put 5 V on a GPIO pin. | It is the one mistake that damages the chip for good. Power sensors and modules from a 3.3 V pin. The 5 V pin powers only a load switched through a MOSFET that draws under about 200 mA, such as lab 6's motor or a relay coil; anything larger gets its own supply, sharing only ground with the board. A servo runs from its own 5 V supply, sharing only ground with the board; only its control signal comes from a pin |
| Never run a motor, relay or solenoid from a GPIO pin. | A pin gives a few milliamps; switch the load with a MOSFET, with a flyback diode across the load's coil, stripe to the positive supply |
| Power off before you rewire. | Shut down with sudo poweroff and wait for the console to show the board has halted, then unplug the USB Type-C supply, change the wiring, check it, and power on. Pulling the plug on a running board can corrupt its boot media |
| Never connect the USB-to-UART adapter's power pin. | Ground, transmit and receive only; the board has its own supply |
| Cross the serial lines. | Adapter transmit to board receive; adapter receive to board transmit |
| Use only 3.3 V USB-to-UART adapters. | The console lines are at the board's 3.3 V logic level |
When it will not boot
| Step | Do this |
|---|---|
| 1 | Watch the serial console while it starts, and note the last line it prints |
| 2 | Swap in the station's spare boot media |
| 3 | Re-write the boot media with the app or the bench PC imager. Re-writing erases everything on it: first copy your own files off, from the board with scp if it still boots, or from the media in the bench PC's card and drive reader |
| 4 | Tell your TA: they start the board over USB and restore its firmware |
| 5 | Hand the board to your TA |