Flashing the Arduino HID

Serial Firmware (the default option)

This operation can be done using your RPi (except Pi Zero W). Here the common steps:

Disconnect the RESET wire from the Arduino board.
Connect the Arduino and RPi with a suitable USB cable.
Log in to the Raspberry Pi using SSH.
Upload the firmware (USB keyboard & mouse is used by default, on this step you can choose PS/2 keyboard):
```
# rw
# systemctl stop kvmd
# cp -r /usr/share/kvmd/hid ~
# cd ~/hid
# make
# make install
# reboot
```
Connect the RESET wire, disconnect the USB cable, and reboot the RPi.

With a Pi Zero W, you may consider building the firmware on a faster system and programming using USB or booting from another SD card and following the build steps using a clone of the KVMD repo.

SPI Firmware

This operation can be done using your Raspberry Pi without disconnecting any wires:

Connect the Arduino and RPi with a suitable USB cable.
Log in to the Raspberry Pi using SSH.
Execute rw, add line dtoverlay=spi0-1cs to /boot/config.txt and perform reboot.

Build and upload the firmware (USB keyboard & mouse is used by default)

# rw
# systemctl stop kvmd
# cp -r /usr/share/kvmd/hid ~
# cd ~/hid
# make spi
# make install
# reboot

Common Errors

Circuit Issues

Common - Reset Wire

Different pins are used for the reset wire but serve a similar function. For programming the TTL firmware over USB, the reset wire should be disconnected. When programming using SPI, the reset wire needs to be connected through a transistor circuit and connected to GPIO25 (pin 22 on the GPIO header)

SPI-specific Wiring

The 3v3, ground, Reset (GPIO25), MISO, MOSI, SCLK, and CS1 need to be connected appropriately. SPIO_CS0 and SPIO_CS1 can both be used but the default configuration uses SPIO_CS1 for the Arduino Microcontroller (CS0 is used for another device on the V3). These generally follow a block as follows:

Pin  0        2         4
      2        0         0
      .........GR.C.......
Row # 12345678901234567890
      ........3MMS........
Pin   0       1          3
       1       7          9

The most common error is an "off-by-one" error where pins are shifted by a row. Some cases have non-standard GPIO layouts so please be careful when following these instructions using a case that has a modified pinout.