> For the complete documentation index, see [llms.txt](https://auvidea.gitbook.io/r20.1-r21-r22-software-setup-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://auvidea.gitbook.io/r20.1-r21-r22-software-setup-guide/guide/r-group-software-setup-guide.md). # R- Group Software Setup Guide ## Flashing to SD-Card Before using the Rxx you will need to prepare a micro SD card for the Raspberry Pi Zero. Start by flashing your micro SD using any flashing tool like the '[Raspberry Pi Imager](https://www.raspberrypi.com/software/)' (available for Linux, Windows and macOS) and select any 32-bit OS – e.g. "Raspberry Pi OS (Legacy) Lite" from 2023-12-05.

### Pre-boot Configuration After your flashing tool is done writing the RPi OS, the config file in the micro SD card's "`bootfs`" (or "`boot`" in older releases) partition needs to be edited before putting it into the RPi Zero – this step is important because otherwise the Pi (depending on the chosen OS version) may not be able to boot. Navigate into the "`bootfs`" partition, open "`config.txt`" and append the following in a new line: ```bash gpio=21=op,dl ```

Now you can put the micro SD card into the Pi Zero and power on the R21. ## Enable I2C Several resources on the carrier board are linked to the Cam I²C, which is hidden by default. ```bash sudo raspi-config ``` `3 Interface Options` → `I5 I2C` → Press Tab, select and to reboot

## Accessing carrier board EEPROM Write protection is activated by default. To deactivate it temporarily, short the pins located 1 CM above the Pi Zero's SD card slot during the writing process. `i2c-tools` are used in this example to read and write data to the EEPROM. This library can be installed with the following commands: ```bash sudo apt update sudo apt install i2c-tools ```

Read or writing to an I²C device is performed with `i2cset` , `i2cget`or `i2ctransfer` on the device address `0x50` and I²C bus `1` More Information about I²C can be found in our [I2C - Guide](https://auvidea.gitbook.io/i2c/) ```bash sudo i2cdetect -y -r 1 ```

```bash sudo i2cdump -y 1 0x50 ```

```bash sudo i2ctransfer -y 1 w5@0x50 0x00 0x54 0x45 0x53 0x54 sudo i2cdump -y 1 0x50 ```

Example write to EEPROM and dump of changed content

The following example tries to overwrite the written data in the previous step without the write protect pin shorted. ```bash sudo i2ctransfer -y 1 w5@0x50 0x00 0xff 0xff 0xff 0xff sudo i2cdump -y 1 0x50 ```

## GPIO Functions ### Command cheat sheet ```bash echo [GPIO_NR] > /sys/class/gpio/export echo out > /sys/class/gpio/gpio[GPIO_NR]/direction echo [0/1] > /sys/class/gpio/gpio[GPIO_NR]/value ``` A more detailed description on how to use GPIO's are described in our [GPIO - Guide](https://auvidea.gitbook.io/gpio/)

Functjion	Default state	Description
RGB LED	Low	GPIO19 = R, GPIO13 = G, GPIO26 = B; high active
USB Hub	High	GPIO16; high active
M.2 LTE	High	GPIO17; high active
M.2 SSD	High	GPIO21; ;disabled by previous modification in "/boot/config.txt"

### Enable/Disable M.2 SSD ```bash echo 21 > /sys/class/gpio/export echo out > /sys/class/gpio/gpio21/direction echo 1 > /sys/class/gpio/gpio21/value # Set GPIO to 1 -> Enable SSD Slot ``` After the enable signal is activated, the USB to PCIe converter is detected as a `JMicron Technology Corp.` device when using the `lsusb` command.

lsusb output before and after enable signal

When using `lsblk` the connected SSD should be identifiable as an `sdx` device. In the following example visible as `/dev/sda`.

### Enabling/Disable M.2 LTE module ```bash echo 17 > /sys/class/gpio/export echo out > /sys/class/gpio/gpio17/direction echo 1 > /sys/class/gpio/gpio17/value # Set GPIO to 1 -> Enable M.2 LTE Slot ``` After the enable signal is activated, the LTE Module used in the following example is detected as `Sierra Wireless Inc.` device when using the `lsusb` command.