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174 lines
6.8 KiB
Markdown
174 lines
6.8 KiB
Markdown
# Raspberry Pi Pico HID
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!!! warning "This page is under construction"
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The Pico HID is a part of DIY PiKVM V1 platform and performs keyboard and mouse emulation.
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It has excellent compatibility, and by default emulates USB, including two mouse modes: absolute and relative.
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The scope of the Pico HID is not limited to V1 platform, it can also be used with V2 and even V3 platform
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if you need to emulate a PS/2 keyboard and mouse or use [legacy multiport KVM switch](https://github.com/pikvm/pikvm/issues/7)
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which does not fully support USB standards.
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This page explains how to build, connect and use all the features of the Pico HID.
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-----
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## Making the Pico HID
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If you are building the PiKVM V1, then all the necessary components should already be at your fingertips.
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If you are making the Pico HID for V2 or V3, then here is what you will need:
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* Raspberry Pi Pico board with soldered pins. [An official green board](https://pico.pinout.xyz) is recommended.
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* *x1* USB-A to Micro-USB cable.
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* *x10* dupont wires female-female.
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* Optional: *x1* 1N5819 diode. But any similar one will do.
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!!! tip "Tip for soldering guru"
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If you know how to solder, you can buy the Pico without pins and no dupond wires, and just solder everything.
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!!! warning
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The diode is needed to provide the power to the Pico HID regardless of the host state,
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and prevents backpowering problem. It will allow you to keep the keyboard buttons pressed
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during the host power cycle, which is important for MacOS to get into the boot menus, for example.
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Do not connect the red wire (the `VSYS (Pico) -> 5V (Pi)` line) without a diode.
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If you can't find the diode, don't connect this wire at all.
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Connect all the parts according to the scheme:
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??? example "Simple wiring diagram"
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<img src="basic_breadboard.png" />
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??? example "Electrical schematic diagram for advanced users"
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<img src="basic_scheme.png" />
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-----
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## Configuring the HID modes
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By default, Pico HID emulates a USB keyboard and an absolute or relative mouse
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(read [here](mouse.md) about the difference between mouse modes).
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For most cases, nothing needs to be changed here. However, if you need something special
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(like Windows 98 support), you can do it without reflashing on the current firmware.
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To achieve this, the Pico HID uses a runtime configuration, which is set by connecting
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some GPIOs with Ground (`GND`) lines.
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| Pin name on the Pico board | Description |
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|----------|-------------|
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| `GP2` | Enable PS/2 keyboard & mouse support (see below). |
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| `GP3` | Prefer the PS/2 keyboard over USB when turning on the HID (if PS/2 enabled). |
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| `GP4` | Prefer the PS/2 mouse over USB (if PS/2 enabled) |
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| `GP6` | Disable USB keyboard & mouse support. This is useful if you only want to use PS/2. |
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| `GP7` | Enable the special USB absolute mouse for Windows 98. |
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| `GP8` | Prefer the relative USB mouse over the absolute one. |
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| `GP9` | Prefer the Windows 98 USB absolute mouse over the regular absolute one (if enabled). |
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!!! example
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To enable Windows 98 absolute mouse, just connect pin `GP9` to any `GND` [on the Pico](https://pico.pinout.xyz).
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!!! warning
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PS/2 is not implemented now. Soon (r) (c) (tm)
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-----
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## Flashing the firmware
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To upload the firmware to Pico HID, you can use any computer with a USB port.
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1. [Download](https://github.com/pikvm/kvmd/releases) the latest release of the firmware. The file is called `pico-hid.uf2`.
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2. Press the white button on the Pico board and plug it using USB cable to the computer.
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3. Release the button.
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4. The Pico board appears as a flash drive on the host computer.
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5. Copy the `pico-hid.uf2` file to this flash drive.
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6. Safely disconnect the USB device.
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-----
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## The final steps
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Connect the Pico HID to the host computer using the USB cable.
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If you are building PiKVM V1, then no further action with the Pico HID is required.
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If you are making the Pico HID for V2 or V3, add the following lines to the PiKVM configuration and reboot it.
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!!! note "KVMD >= 3.241 is required for the Pico HID"
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* `/boot/config.txt`
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```ini
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dtoverlay=spi0-1cs
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```
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* `/etc/kvmd/override.yaml`:
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```yaml
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kvmd:
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hid:
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type: spi
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chip: 0
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bus: 0
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sw_cs_pin: 7
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sw_cs_per_byte: true
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reset_pin: 25
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reset_inverted: true
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reset_self: true
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power_detect_pin: 16
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power_detect_pull_down: true
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```
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-----
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## Replacing the legacy Arduino HID
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!!! warning
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**This section is intended for advanced users of the [legacy Arduino HID](arduino_hid.md).**
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It may seem tempting, but **don't to use the Arduino HID for new PiKVM builds**
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just because you have it at your fingertips. Connecting and flashing Arduino
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is much more time consuming than Pico. In addition, different Arduino board works
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with different voltages, may or may not have SPI (for the Pico, we use SPI to free up
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the UART on Raspberry Pi for the console and other useful things), etc.
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Using the Pico HID is the recommended fast and standard way in the PiKVM world.
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The Pico HID can be used to replace the [legacy Arduino HID](arduino_hid.md).
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Moreover, it can use both Serial (UART) port and SPI. The connection scheme is also noticeably simplified,
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getting rid of the transistor for the Reset line and level shifter for RX/TX (MOSI/MISO).
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??? example "For the Arduino HID over SPI"
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Throw away the Reset transistor and level shifter, and follow this guide
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from the very beginning, as if you were connecting Pico HID for V2/V3.
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??? example "For the classic Serial (UART) HID"
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Get rid of the transistor and level shifter, and follow this guide
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from the very beginning, but the schemes and configs will be slightly different.
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* The `GP22` on the Pico is connected directly to the `GND`. This enables UART mode instead of default SPI.
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* In the original V0, `GPIO4` [on the Raspberry Pi](https://pinout.xyz) was used for the Reset line.
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Now we recommend to use `GPIO25` for consistency reasons.
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However, you can use `GPIO4` by changing the `reset_pin` value in the config example below.
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On the scheme, this is a yellow wire, the `RUN (Pico) -> GPIO25 (Pi)` line.
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??? example "Simple wiring diagram"
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<img src="serial_breadboard.png" />
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??? example "Electrical schematic diagram"
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<img src="serial_scheme.png" />
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??? example "Configs"
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* Don't add line `dtoverlay=spi0-1cs` to the `/boot/config.txt` file. It's only needed for SPI.
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* `/etc/kvmd/override.yaml`:
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```yaml
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kvmd:
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hid:
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type: serial
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device: /dev/kvmd-hid
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reset_pin: 25
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reset_inverted: true
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reset_self: true
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power_detect_pin: 16
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power_detect_pull_down: true
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```
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