Module 0 · Lab 1
First boot
Before any theory, every pair gets a board running and records what it says on the way up. The boot log captured here is the map for the next eight modules.
Key ideas
- A single-board computer is a whole computer on one circuit board. Unlike a microcontroller, it runs a general-purpose operating system from removable or on-board storage.
- An OS image is a byte-for-byte copy of a disk. A SHA-256 checksum proves the image file you have is the one that was published; the imager's verify step, or the app's checked write, confirms that what landed on the drive or card matches it.
- The serial console is the board's text output on two signal wires plus ground. It works before the display, the network or even memory are up, which makes it the most important instrument in the course.
- The shell is the way in: files, processes,
/proc,/sysand/devare where Linux shows you the hardware.
The shell commands lab 1 uses
Type man <command> on the board for any of them.
| Command | What it does |
|---|---|
sha256sum <file> | Prints a file's SHA-256 checksum, to compare with the published one |
ls, cd, cat <file> | List a directory, change into one, print a file; cat /proc/cpuinfo shows the CPU |
ip addr | The board's network interfaces and their addresses |
ssh <user>@<address> | Log in to the board over the network from the bench PC |
scp <file> <user>@<address>: | Copy a file from the bench PC to the board |
scp <user>@<address>:<file> . | Run on the bench PC: copy a file from the board to the bench PC's current directory |
sudo <command> | Run one command with administrator rights; it asks for your password |
sudo apt install ./*.deb | Install every package file in the current directory at once, so packages that depend on each other are matched |
On the bench
In short, what you do in lab 1, where the steps are given in full:
- Write an image to a USB flash drive with the Libre Computer app for Android or a desktop imager, as your bench describes, and check its SHA-256 against the published value. Das Frite has no card slot: its UEFI firmware in SPI flash boots the OS from the USB drive.
- Connect a 3.3 V USB-to-UART adapter to the 40-pin header: the adapter's ground to pin 6, the adapter's receive to the board's transmit on pin 5, and the adapter's transmit to the board's receive on pin 3. Never connect the adapter's power pin.
- Open a terminal at 115200 baud, 8 data bits, no parity, 1 stop bit, then apply power and save everything the board prints.
- Log in on the console with the image's default login, find the board's address, and log in again over SSH.
- Keep the raw log. It is annotated in labs 3, 4 and 5.
On the bench
In short, what you do in lab 1, where the steps are given in full:
- Write an image to a microSD card with the Libre Computer app for Android or a desktop imager, as your bench describes, and check its SHA-256 against the published value.
- Connect a 3.3 V USB-to-UART adapter to the board's 3-pin UART header: ground to pin 1, the adapter's receive to the board's transmit on pin 2, and the adapter's transmit to the board's receive on pin 3. Never connect the adapter's power pin.
- Open a terminal at 115200 baud, 8 data bits, no parity, 1 stop bit, then apply power and save everything the board prints.
- Log in on the console with the image's default login, find the board's address, and log in again over SSH.
- Keep the raw log. It is annotated in labs 3, 4 and 5.
Resources
| Resource | Use in this module |
|---|---|
| libre.computer downloads | OS images, checksums and desktop imager instructions |
| Das Frite GPIO pinout | The header, the console pins and the 3.3 V limit |
| Libre Computer boards overview and resources | Every board's guides in one place |
Resources
| Resource | Use in this module |
|---|---|
| libre.computer downloads | OS images, checksums and desktop imager instructions |
| Solitude GPIO pinout | The header, the UART header and the 3.3 V limit |
| Solitude overview, resources and guides | Getting-started guides for Solitude |