pikvm/docs/flashing_hid.md

!!! warning "Legacy warning" This page describes the legacy keyboard and mouse emulator used in old DIY builds. There is no point using it today because there is a more modern and better replacement for the new Pico HID. This one can also serve as an in-place compatible replacement for the Arduino HID in the old build.

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:

1. Disconnect the RESET wire from the Arduino board.

2. Connect the Arduino and RPi with a suitable USB cable.

3. Log in to the Raspberry Pi using SSH.

4. 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/arduino ~
   # cd ~/hid
   # make
   # make install
   # reboot
   

5. 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:

1. Connect the Arduino and RPi with a suitable USB cable.

2. Log in to the Raspberry Pi using SSH.

3. Execute rw, add line dtoverlay=spi0-1cs to /boot/config.txt and perform reboot.

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

   # rw
   # systemctl stop kvmd
   # cp -r /usr/share/kvmd/hid/arduino ~
   # 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.