[Core] Add Raspberry Pi RP2040 support (#14877)

* Disable RESET keycode because of naming conflicts

* Add Pico SDK as submodule

* Add RP2040 build support to QMK

* Adjust USB endpoint structs for RP2040

* Add RP2040 bootloader and double-tap reset routine

* Add generic and pro micro RP2040 boards

* Add RP2040 onekey keyboard

* Add WS2812 PIO DMA enabled driver and documentation

Supports regular and open-drain output configuration. RP2040 GPIOs are
sadly not 5V tolerant, so this is a bit use-less or needs extra hardware
or you take the risk to fry your hardware.

* Adjust SIO Driver for RP2040

* Adjust I2C Driver for RP2040

* Adjust SPI Driver for RP2040

* Add PIO serial driver and documentation

* Add general RP2040 documentation

* Apply suggestions from code review

Co-authored-by: Nick Brassel <nick@tzarc.org>

Co-authored-by: Nick Brassel <nick@tzarc.org>

43 files changed, 2025 insertions, 96 deletions

diff --git a/.gitmodules b/.gitmodules
index 681693a5a4..48c7035afa 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -18,3 +18,6 @@
 [submodule "lib/printf"]
 	path = lib/printf
 	url = https://github.com/qmk/printf
+[submodule "lib/pico-sdk"]
+	path = lib/pico-sdk
+	url = https://github.com/qmk/pico-sdk.git
diff --git a/Makefile b/Makefile
index 4c2e6a04dc..fc6d016448 100644
--- a/Makefile
+++ b/Makefile
@@ -401,6 +401,7 @@ ifndef SKIP_GIT
 	if [ ! -e lib/lufa ]; then git submodule sync lib/lufa && git submodule update --depth 50 --init lib/lufa; fi
 	if [ ! -e lib/vusb ]; then git submodule sync lib/vusb && git submodule update --depth 50 --init lib/vusb; fi
 	if [ ! -e lib/printf ]; then git submodule sync lib/printf && git submodule update --depth 50 --init lib/printf; fi
+	if [ ! -e lib/pico-sdk ]; then git submodule sync lib/pico-sdk && git submodule update --depth 50 --init lib/pico-sdk; fi
 	git submodule status --recursive 2>/dev/null | \
 	while IFS= read -r x; do \
 		case "$$x" in \
diff --git a/builddefs/bootloader.mk b/builddefs/bootloader.mk
index eba8e280e4..3d4c03b01c 100644
--- a/builddefs/bootloader.mk
+++ b/builddefs/bootloader.mk
@@ -200,6 +200,10 @@ ifeq ($(strip $(BOOTLOADER)), tinyuf2)
     OPT_DEFS += -DBOOTLOADER_TINYUF2
     BOOTLOADER_TYPE = tinyuf2
 endif
+ifeq ($(strip $(BOOTLOADER)), rp2040)
+    OPT_DEFS += -DBOOTLOADER_RP2040
+    BOOTLOADER_TYPE = rp2040
+endif
 ifeq ($(strip $(BOOTLOADER)), halfkay)
     OPT_DEFS += -DBOOTLOADER_HALFKAY
     BOOTLOADER_TYPE = halfkay
diff --git a/builddefs/common_features.mk b/builddefs/common_features.mk
index b447c6743d..2edc1bdef0 100644
--- a/builddefs/common_features.mk
+++ b/builddefs/common_features.mk
@@ -547,7 +547,7 @@ ifeq ($(strip $(BACKLIGHT_ENABLE)), yes)
     endif
 endif
 
-VALID_WS2812_DRIVER_TYPES := bitbang pwm spi i2c
+VALID_WS2812_DRIVER_TYPES := bitbang pwm spi i2c vendor
 
 WS2812_DRIVER ?= bitbang
 ifeq ($(strip $(WS2812_DRIVER_REQUIRED)), yes)
@@ -637,7 +637,7 @@ ifneq ($(strip $(DEBOUNCE_TYPE)), custom)
 endif
 
 
-VALID_SERIAL_DRIVER_TYPES := bitbang usart
+VALID_SERIAL_DRIVER_TYPES := bitbang usart vendor
 
 SERIAL_DRIVER ?= bitbang
 ifeq ($(filter $(SERIAL_DRIVER),$(VALID_SERIAL_DRIVER_TYPES)),)
diff --git a/builddefs/mcu_selection.mk b/builddefs/mcu_selection.mk
index d5fb731e08..d676e0c06a 100644
--- a/builddefs/mcu_selection.mk
+++ b/builddefs/mcu_selection.mk
@@ -116,6 +116,41 @@ ifneq ($(findstring MK66FX1M0, $(MCU)),)
   BOARD ?= PJRC_TEENSY_3_6
 endif
 
+ifneq ($(findstring RP2040, $(MCU)),)
+  # Cortex version
+  MCU = cortex-m0plus
+
+  # ARM version, CORTEX-M0/M1 are 6, CORTEX-M3/M4/M7 are 7
+  CHIBIOS_PORT = ARMv6-M-RP2
+
+  ## chip/board settings
+  # - the next two should match the directories in
+  #   <chibios[-contrib]>/os/hal/ports/$(MCU_PORT_NAME)/$(MCU_SERIES)
+  #   OR
+  #   <chibios[-contrib]>/os/hal/ports/$(MCU_FAMILY)/$(MCU_SERIES)
+  MCU_FAMILY = RP
+  MCU_SERIES = RP2040
+
+  # Linker script to use
+  # - it should exist either in <chibios>/os/common/ports/ARMCMx/compilers/GCC/ld/
+  #   or <keyboard_dir>/ld/
+  STARTUPLD_CONTRIB = $(CHIBIOS_CONTRIB)/os/common/startup/ARMCMx/compilers/GCC/ld
+  MCU_LDSCRIPT ?= RP2040_FLASH
+  LDFLAGS += -L $(STARTUPLD_CONTRIB)
+
+  # Startup code to use
+  #  - it should exist in <chibios>/os/common/startup/ARMCMx/compilers/GCC/mk/
+  MCU_STARTUP ?= rp2040
+
+  # Board: it should exist either in <chibios>/os/hal/boards/,
+  # <keyboard_dir>/boards/, or drivers/boards/
+  BOARD ?= GENERIC_PROMICRO_RP2040
+
+  # Default UF2 Bootloader settings
+  UF2_FAMILY ?= RP2040
+  FIRMWARE_FORMAT ?= uf2
+endif
+
 ifneq ($(findstring STM32F042, $(MCU)),)
   # Cortex version
   MCU = cortex-m0
diff --git a/data/schemas/definitions.jsonschema b/data/schemas/definitions.jsonschema
index 2cf76a351c..8b68a58482 100644
--- a/data/schemas/definitions.jsonschema
+++ b/data/schemas/definitions.jsonschema
@@ -102,6 +102,10 @@
                 "pattern": "^LINE_PIN\\d{1,2}$"
             },
             {
+                "type": "string",
+                "pattern": "^GP\\d{1,2}$"
+            },
+            {
                 "type": "integer"
             },
             {
diff --git a/data/schemas/keyboard.jsonschema b/data/schemas/keyboard.jsonschema
index ec5377b3b3..8aca807e38 100644
--- a/data/schemas/keyboard.jsonschema
+++ b/data/schemas/keyboard.jsonschema
@@ -42,7 +42,7 @@
         },
         "processor": {
             "type": "string",
-            "enum": ["cortex-m0", "cortex-m0plus", "cortex-m3", "cortex-m4", "MKL26Z64", "MK20DX128", "MK20DX256", "MK66FX1M0", "STM32F042", "STM32F072", "STM32F103", "STM32F303", "STM32F401", "STM32F405", "STM32F407", "STM32F411", "STM32F446", "STM32G431", "STM32G474", "STM32L412", "STM32L422", "STM32L432", "STM32L433", "STM32L442", "STM32L443", "GD32VF103", "WB32F3G71", "WB32FQ95", "atmega16u2", "atmega32u2", "atmega16u4", "atmega32u4", "at90usb162", "at90usb646", "at90usb647", "at90usb1286", "at90usb1287", "atmega32a", "atmega328p", "atmega328", "attiny85", "unknown"]
+            "enum": ["cortex-m0", "cortex-m0plus", "cortex-m3", "cortex-m4", "MKL26Z64", "MK20DX128", "MK20DX256", "MK66FX1M0", "RP2040", "STM32F042", "STM32F072", "STM32F103", "STM32F303", "STM32F401", "STM32F405", "STM32F407", "STM32F411", "STM32F446", "STM32G431", "STM32G474", "STM32L412", "STM32L422", "STM32L432", "STM32L433", "STM32L442", "STM32L443", "GD32VF103", "WB32F3G71", "WB32FQ95", "atmega16u2", "atmega32u2", "atmega16u4", "atmega32u4", "at90usb162", "at90usb646", "at90usb647", "at90usb1286", "at90usb1287", "atmega32a", "atmega328p", "atmega328", "attiny85", "unknown"]
         },
         "audio": {
             "type": "object",
@@ -86,7 +86,7 @@
         },
         "bootloader": {
             "type": "string",
-            "enum": ["atmel-dfu", "bootloadhid", "bootloadHID", "custom", "caterina", "halfkay", "kiibohd", "lufa-dfu", "lufa-ms", "md-boot", "qmk-dfu", "qmk-hid", "stm32-dfu", "stm32duino", "gd32v-dfu", "wb32-dfu", "unknown", "usbasploader", "USBasp", "tinyuf2"],
+            "enum": ["atmel-dfu", "bootloadhid", "bootloadHID", "custom", "caterina", "halfkay", "kiibohd", "lufa-dfu", "lufa-ms", "md-boot", "qmk-dfu", "qmk-hid", "stm32-dfu", "stm32duino", "gd32v-dfu", "wb32-dfu", "unknown", "usbasploader", "USBasp", "tinyuf2", "rp2040"],
         },
         "bootloader_instructions": {
             "type": "string",
diff --git a/docs/_summary.md b/docs/_summary.md
index e6d636402b..da007bccb6 100644
--- a/docs/_summary.md
+++ b/docs/_summary.md
@@ -165,6 +165,7 @@
     * Arm/ChibiOS
       * [Selecting an MCU](platformdev_selecting_arm_mcu.md)
       * [Early initialization](platformdev_chibios_earlyinit.md)
+      * [Raspberry Pi RP2040](platformdev_rp2040.md)
 
   * QMK Reference
     * [Contributing to QMK](contributing.md)
diff --git a/docs/compatible_microcontrollers.md b/docs/compatible_microcontrollers.md
index cee8986829..a594fe0620 100644
--- a/docs/compatible_microcontrollers.md
+++ b/docs/compatible_microcontrollers.md
@@ -65,6 +65,12 @@ You can also use any ARM chip with USB that [ChibiOS](https://www.chibios.org) s
  * [MK66FX1M0](https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mcus/k-series-cortex-m4/k6x-ethernet/kinetis-k66-180-mhz-dual-high-speed-full-speed-usbs-2mb-flash-microcontrollers-mcus-based-on-arm-cortex-m4-core:K66_180)
    * PJRC Teensy 3.6
 
+### Raspberry Pi
+
+* [RP2040](https://www.raspberrypi.com/documentation/microcontrollers/rp2040.html)
+
+For a detailed overview about the RP2040 support by QMK see the [dedicated RP2040 page](platformdev_rp2040.md).
+
 ## Atmel ATSAM
 
 There is limited support for one of Atmel's ATSAM microcontrollers, that being the [ATSAMD51J18A](https://www.microchip.com/wwwproducts/en/ATSAMD51J18A) used by the [Massdrop keyboards](https://github.com/qmk/qmk_firmware/tree/master/keyboards/massdrop). However, it is not recommended to design a board with this microcontroller as the support is quite specialized to Massdrop hardware.
diff --git a/docs/flashing.md b/docs/flashing.md
index dfb255f2dc..5e5dcb34e4 100644
--- a/docs/flashing.md
+++ b/docs/flashing.md
@@ -362,3 +362,42 @@ CLI Flashing sequence:
 ### `make` Targets
 
 * `:uf2-split-left` and `:uf2-split-right`: Flashes the firmware but also sets the handedness setting in EEPROM by generating a side specific firmware.
+
+## Raspberry Pi RP2040 UF2
+
+The `rules.mk` setting for this bootloader is `rp2040`, and can be specified at the keymap or user level.
+
+To ensure compatibility with the rp2040 bootloader, make sure this block is present in your `rules.mk`:
+
+```make
+# Bootloader selection
+BOOTLOADER = rp2040
+```
+
+Compatible flashers:
+
+* Any application able to copy a file from one place to another, such as _macOS Finder_ or _Windows Explorer_.
+
+Flashing sequence:
+
+1. Enter the bootloader using any of the following methods:
+    * Tap the `QK_BOOTLOADER` keycode
+    * Hold the `BOOTSEL` button on the PCB while plugin in the usb cable.
+    * Double-tap the `RESET` button on the PCB<sup>1</sup>.
+2. Wait for the OS to detect the device
+3. Copy the .uf2 file to the new USB disk
+4. Wait for the keyboard to become available
+
+or
+
+CLI Flashing sequence:
+
+1. Enter the bootloader using any of the following methods:
+    * Tap the `QK_BOOTLOADER` keycode
+    * Hold the `BOOTSEL` button on the PCB while plugin in the usb cable.
+    * Double-tap the `RESET` button on the PCB<sup>1</sup>.
+2. Wait for the OS to detect the device
+3. Flash via QMK CLI eg. `qmk flash --keyboard handwired/onekey/rpi_pico --keymap default`
+4. Wait for the keyboard to become available
+
+<sup>1</sup>: This works only if QMK was compiled with `RP2040_BOOTLOADER_DOUBLE_TAP_RESET` defined.
diff --git a/docs/platformdev_rp2040.md b/docs/platformdev_rp2040.md
new file mode 100644
index 0000000000..9426efa29a
--- /dev/null
+++ b/docs/platformdev_rp2040.md
@@ -0,0 +1,125 @@
+# Raspberry Pi RP2040
+
+The following table shows the current driver status for peripherals on RP2040 MCUs:
+
+| System                               | Support                                        |
+| ------------------------------------ | ---------------------------------------------- |
+| [ADC driver](adc_driver.md)          | Support planned (no ETA)                       |
+| [Audio](audio_driver.md)             | Support planned (no ETA)                       |
+| [I2C driver](i2c_driver.md)          | :heavy_check_mark:                             |
+| [SPI driver](spi_driver.md)          | :heavy_check_mark:                             |
+| [WS2812 driver](ws2812_driver.md)    | :heavy_check_mark: using `PIO` driver          |
+| [External EEPROMs](eeprom_driver.md) | :heavy_check_mark: using `I2C` or `SPI` driver |
+| [EEPROM emulation](eeprom_driver.md) | Support planned (no ETA)                       |
+| [serial driver](serial_driver.md)    | :heavy_check_mark: using `SIO` or `PIO` driver |
+| [UART driver](uart_driver.md)        | Support planned (no ETA)                       |
+
+## GPIO
+
+<img alt="Raspberry Pi Pico pinout" src="https://i.imgur.com/nLaiYDE.jpg" width="48%"/>
+<img alt="Sparkfun RP2040 Pro Micro pinout" src="https://i.imgur.com/1TPAhrs.jpg" width="48%"/>
+
+!> The GPIO pins of the RP2040 are not 5V tolerant!
+
+### Pin nomenclature
+
+To address individual pins on the RP2040, QMK uses the `GPx` abbreviation -- where the `x` stands for the GPIO number of the pin. This number can likely be found on the official pinout diagram of your board. Note that these GPIO numbers match the RP2040 MCU datasheet, and don't necessarily match the number you see printed on the board. For instance the Raspberry Pi Pico uses numbers from 1 to 40 for their pins, but these are not identical to the RP2040's GPIO numbers. So if you want to use the pin 11 of the Pico for your keyboard, you would refer to it as `GP8` in the config files.
+
+### Alternate functions
+
+The RP2040 features flexible GPIO function multiplexing, this means that every pin can be connected to nearly all the internal peripherals like I2C, SPI, UART or PWM. This allows for flexible PCB designs that are much less restricted in the selection of GPIO pins. To find out which pin can use which peripheral refer to the official [Raspberry PI RP2040 datasheet](https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf#page=14) section 1.4.3 GPIO functions.
+
+## Selecting hardware peripherals and drivers
+
+QMK RP2040 support builds upon ChibiOS and thus follows their convention for activating drivers and associated hardware peripherals. These tables only give a quick overview which values have to be used, please refer to the ChibiOS specific sections on the driver pages.
+
+### I2C Driver
+
+| RP2040 Peripheral | `mcuconf.h` values | `I2C_DRIVER` |
+| ----------------- | ------------------ | ------------ |
+| `I2C0`            | `RP_I2C_USE_I2C0`  | `I2CD1`      |
+| `I2C1`            | `RP_I2C_USE_I2C1`  | `I2CD2`      |
+
+To configure the I2C driver please read the [ChibiOS/ARM](i2c_driver.md#arm-configuration) section.
+
+### SPI Driver
+
+| RP2040 Peripheral | `mcuconf.h` values | `SPI_DRIVER` |
+| ----------------- | ------------------ | ------------ |
+| `SPI0`            | `RP_SPI_USE_SPI0`  | `SPID0`      |
+| `SPI1`            | `RP_SPI_USE_SPI1`  | `SPID1`      |
+
+To configure the SPI driver please read the [ChibiOS/ARM](spi_driver.md#chibiosarm-configuration) section.
+
+## Double-tap reset boot-loader entry :id=double-tap
+
+The double-tap reset mechanism is an alternate way in QMK to enter the embedded mass storage UF2 boot-loader of the RP2040. It enables bootloader entry by a fast double-tap of the reset pin on start up, which is similar to the behavior of AVR Pro Micros. This feature activated by default for the Pro Micro RP2040 board, but has to be configured for other boards. To activate it, add the following options to your keyboards `config.h` file:
+
+```c
+#define RP2040_BOOTLOADER_DOUBLE_TAP_RESET // Activates the double-tap behavior
+#define RP2040_BOOTLOADER_DOUBLE_TAP_RESET_TIMEOUT 200U // Timeout window in ms in which the double tap can occur.
+#define RP2040_BOOTLOADER_DOUBLE_TAP_RESET_LED_MASK 0U // Specify a optional status led which blinks when entering the bootloader
+```
+
+## Pre-defined RP2040 boards
+
+QMK defines two boards that you can choose from to base your RP2040 powered keyboard upon. These boards provide pre-configured default pins and drivers.
+
+### Generic Pro Micro RP2040
+
+This is the default board that is chosen, unless any other RP2040 board is selected in your keyboards `rules.mk` file. It assumes a pin layout for the I2C, SPI and Serial drivers which is identical to the Sparkfun Pro Micro RP2040, however all values can be overwritten by defining them in your keyboards `config.h` file. The [double-tap](#double-tap) reset to enter boot-loader behavior is activated by default.
+
+
+| Driver configuration define                                                | Value                                |
+| -------------------------------------------------------------------------- | ------------------------------------ |
+| **I2C driver**                                                             |                                      |
+| `I2C_DRIVER`                                                               | `I2CD2`                              |
+| `I2C1_SDA_PIN`                                                             | `GP2`                                |
+| `I2C1_SCL_PIN`                                                             | `GP3`                                |
+| **SPI driver**                                                             |                                      |
+| `SPI_DRIVER`                                                               | `SPID0`                              |
+| `SPI_SCK_PIN`                                                              | `GP18`                               |
+| `SPI_MISO_PIN`                                                             | `GP20`                               |
+| `SPI_MOSI_PIN`                                                             | `GP19`                               |
+| **Serial driver**                                                          |                                      |
+| `SERIAL_USART_DRIVER` ([SIO Driver](serial_driver.md#the-sio-driver) only) | `SIOD0`                              |
+| `SOFT_SERIAL_PIN`                                                          | undefined, use `SERIAL_USART_TX_PIN` |
+| `SERIAL_USART_TX_PIN`                                                      | `GP0`                                |
+| `SERIAL_USART_RX_PIN`                                                      | `GP1`                                |
+
+?> The pin-outs of Adafruit's KB2040 and Boardsource's Blok both deviate from the Sparkfun Pro Micro RP2040. Lookup the pin-out of these boards and adjust your keyboards pin definition accordingly if you want to use these boards.
+
+### Generic RP2040 board
+
+This board can be chosen as a base for RP2040 keyboards which configure all necessary pins and drivers themselves and do not wish to leverage the configuration matching the Generic Pro Micro RP2040 board. Thus it doesn't provide any pre-configured pins or drivers. To select this board add the following line to your keyboards `rules.mk` file.
+
+```make
+BOARD = GENERIC_RP_RP2040
+```
+
+## Split keyboard support
+
+Split keyboards are fully supported using the [serial driver](serial_driver.md) in both full-duplex and half-duplex configurations. Two driver subsystems are supported by the RP2040, the hardware UART based `SIO` and the Programmable IO based `PIO` driver.
+
+| Feature                       | [SIO Driver](serial_driver.md#the-sio-driver) | [PIO Driver](serial_driver.md#the-pio-driver) |
+| ----------------------------- | --------------------------------------------- | --------------------------------------------- |
+| Half-Duplex operation         |                                               | :heavy_check_mark:                            |
+| Full-Duplex operation         | :heavy_check_mark:                            | :heavy_check_mark:                            |
+| `TX` and `RX` pin swapping    |                                               | :heavy_check_mark:                            |
+| Any GPIO as `TX` and `RX` pin | Only UART capable pins                        | :heavy_check_mark:                            |
+| Simple configuration          |                                               | :heavy_check_mark:                            |
+
+The `PIO` driver is much more flexible then the `SIO` driver, the only "downside" is the usage of `PIO` resources which in turn are not available for advanced user programs. Under normal circumstances, this resource allocation will be a non-issue.
+
+## RP2040 second stage bootloader selection
+
+As the RP2040 does not have any internal flash memory it depends on an external SPI flash memory chip to store and execute instructions from. To successfully interact with a wide variety of these chips a second stage bootloader that is compatible with the chosen external flash memory has to be supplied with each firmware image. By default an `W25Q080` compatible bootloader is assumed, but others can be chosen by adding one of the defines listed in the table below to your keyboards `config.h` file. 
+
+| Compatible with flash chip | Selection                          |
+| :------------------------- | ---------------------------------- |
+| W25Q080                    | Selected by default                |
+| AT25SF128A                 | `#define RP2040_FLASH_AT25SF128A`  |
+| GD25Q64CS                  | `#define RP2040_FLASH_GD25Q64CS`   |
+| W25X10CL                   | `#define RP2040_FLASH_W25X10CL`    |
+| IS25LP080                  | `#define RP2040_FLASH_IS25LP080`   |
+| Generic 03H flash          | `#define RP2040_FLASH_GENERIC_03H` |
diff --git a/docs/serial_driver.md b/docs/serial_driver.md
index 7c0daec9b1..fff63109a1 100644
--- a/docs/serial_driver.md
+++ b/docs/serial_driver.md
@@ -74,11 +74,11 @@ Targeting ARM boards based on ChibiOS, where communication is offloaded to a USA
 +-------+                 +-------+
 ```
 
-Only one GPIO pin is needed for the Half-duplex driver, as only one wire is used for receiving and transmitting data. This pin is refereed to as the `SERIAL_USART_TX_PIN` in the configuration. Take care that the pin you chose can act as the TX pin of the USART peripheral. A simple TRS or USB cable provides enough conductors for this driver to work. As the split connection is configured to work in open-drain mode, an **external pull-up resistor is needed to keep the line high**. Resistor values of 1.5kΩ to 8.2kΩ are known to work.
+Only one GPIO pin is needed for the Half-duplex driver, as only one wire is used for receiving and transmitting data. This pin is referred to as the `SERIAL_USART_TX_PIN` in the configuration. Take care that the pin you chose can act as the TX pin of the USART peripheral. A simple TRS or USB cable provides enough conductors for this driver to work. As the split connection is configured to work in open-drain mode, an **external pull-up resistor is needed to keep the line high**. Resistor values of 1.5kΩ to 8.2kΩ are known to work.
 
 ### Setup
 
-To use the Half-duplex driver follow these steps to activate it.
+To use the Half-duplex driver follow these steps to activate it. If you target the Raspberry Pi RP2040 PIO implementation skip step 1.
 
 1. Change the `SERIAL_DRIVER` to `usart` in your keyboards `rules.mk` file:
 
@@ -86,7 +86,13 @@ To use the Half-duplex driver follow these steps to activate it.
 SERIAL_DRIVER = usart
 ```
 
-2. Configure the hardware of your keyboard via the `config.h` file:
+2. (RP2040 PIO only!) Change the `SERIAL_DRIVER` to `vendor` in your keyboards `rules.mk` file:
+
+```make
+SERIAL_DRIVER = vendor
+```
+
+3. Configure the hardware of your keyboard via the `config.h` file:
 
 ```c
 #define SERIAL_USART_TX_PIN B6     // The GPIO pin that is used split communication.
@@ -99,7 +105,7 @@ For STM32 MCUs several GPIO configuration options can be changed as well. See th
 #define SERIAL_USART_TX_PAL_MODE 7 // Pin "alternate function", see the respective datasheet for the appropriate values for your MCU. default: 7
 ```
 
-3. Decide either for ChibiOS `SERIAL` or `SIO` subsystem, see the section ["Choosing a ChibiOS driver subsystem"](#choosing-a-chibios-driver-subsystem).
+1. Decide either for `SERIAL`, `SIO` or `PIO` subsystem, see the section ["Choosing a driver subsystem"](#choosing-a-driver-subsystem).
 
 <hr>
 
@@ -125,11 +131,11 @@ Targeting ARM boards based on ChibiOS where communication is offloaded to an USA
 
 Two GPIO pins are needed for the Full-duplex driver, as two distinct wires are used for receiving and transmitting data. The pin transmitting data is the `TX` pin and refereed to as the `SERIAL_USART_TX_PIN`, the pin receiving data is the `RX` pin and refereed to as the `SERIAL_USART_RX_PIN` in this configuration. Please note that `TX` pin of the master half has to be connected with the `RX` pin of the slave half and the `RX` pin of the master half has to be connected with the `TX` pin of the slave half! Usually this pin swap has to be done outside of the MCU e.g. with cables or on the PCB. Some MCUs like the STM32F303 used on the Proton-C allow this pin swap directly inside the MCU. A simple TRRS or USB cable provides enough conductors for this driver to work.
 
-To use this driver the usart peripherals `TX` and `RX` pins must be configured with the correct Alternate-functions. If you are using a Proton-C everything is already setup, same is true for STM32F103 MCUs. For MCUs which are using a modern flexible GPIO configuration you have to specify these by setting `SERIAL_USART_TX_PAL_MODE` and `SERIAL_USART_RX_PAL_MODE`. Reefer to the corresponding datasheets of your MCU or find those settings in the section ["Alternate Functions for selected STM32 MCUs"](#alternate-functions-for-selected-stm32-mcus).
+To use this driver the usart peripherals `TX` and `RX` pins must be configured with the correct Alternate-functions. If you are using a Proton-C everything is already setup, same is true for STM32F103 MCUs. For MCUs which are using a modern flexible GPIO configuration you have to specify these by setting `SERIAL_USART_TX_PAL_MODE` and `SERIAL_USART_RX_PAL_MODE`. Refer to the corresponding datasheets of your MCU or find those settings in the section ["Alternate Functions for selected STM32 MCUs"](#alternate-functions-for-selected-stm32-mcus).
 
 ### Setup
 
-To use the Full-duplex driver follow these steps to activate it.
+To use the Full-duplex driver follow these steps to activate it. If you target the Raspberry Pi RP2040 PIO implementation skip step 1.
 
 1. Change the `SERIAL_DRIVER` to `usart` in your keyboards `rules.mk` file:
 
@@ -137,7 +143,13 @@ To use the Full-duplex driver follow these steps to activate it.
 SERIAL_DRIVER = usart
 ```
 
-2. Configure the hardware of your keyboard via the `config.h` file:
+2. (RP2040 PIO only!) Change the `SERIAL_DRIVER` to `vendor` in your keyboards `rules.mk` file:
+
+```make
+SERIAL_DRIVER = vendor
+```
+
+3. Configure the hardware of your keyboard via the `config.h` file:
 
 ```c
 #define SERIAL_USART_FULL_DUPLEX   // Enable full duplex operation mode.
@@ -153,11 +165,11 @@ For STM32 MCUs several GPIO configuration options, including the ability for `TX
 #define SERIAL_USART_TX_PAL_MODE 7 // Pin "alternate function", see the respective datasheet for the appropriate values for your MCU. default: 7
 ```
 
-3. Decide either for ChibiOS `SERIAL` or `SIO` subsystem, see the section ["Choosing a ChibiOS driver subsystem"](#choosing-a-chibios-driver-subsystem).
+1. Decide either for `SERIAL`, `SIO` or `PIO` subsystem, see the section ["Choosing a driver subsystem"](#choosing-a-driver-subsystem).
 
 <hr>
 
-## Choosing a ChibiOS driver subsystem
+## Choosing a driver subsystem
 
 ### The `SERIAL` driver
 
@@ -219,6 +231,17 @@ Where 'n' matches the peripheral number of your selected USART on the MCU.
  #define SERIAL_USART_DRIVER SIOD3
  ```
  
+### The `PIO` driver
+
+The `PIO` subsystem is a Raspberry Pi RP2040 specific implementation, using the integrated PIO peripheral and is therefore only available on this MCU. Because of the flexible nature of the PIO peripherals, **any** GPIO pin can be used as a `TX` or `RX` pin. Half-duplex and Full-duplex operation is fully supported. The Half-duplex operation mode uses the built-in pull-ups and GPIO manipulation on the RP2040 to drive the line high by default. An external pull-up is therefore not necessary.
+
+Configure the hardware via your config.h:
+```c
+#define SERIAL_PIO_USE_PIO1 // Force the usage of PIO1 peripheral, by default the Serial implementation uses the PIO0 peripheral
+```
+
+The Serial PIO program uses 2 state machines, 13 instructions and the complete interrupt handler of the PIO peripheral it is running on.
+
 <hr>
 
 ## Advanced Configuration
diff --git a/docs/ws2812_driver.md b/docs/ws2812_driver.md
index 8acac0b3aa..54e6e77d81 100644
--- a/docs/ws2812_driver.md
+++ b/docs/ws2812_driver.md
@@ -11,11 +11,12 @@ These LEDs are called "addressable" because instead of using a wire per color, e
 ## Supported Driver Types
 
 |          | AVR                | ARM                |
-|----------|--------------------|--------------------|
+| -------- | ------------------ | ------------------ |
 | bit bang | :heavy_check_mark: | :heavy_check_mark: |
 | I2C      | :heavy_check_mark: |                    |
 | SPI      |                    | :heavy_check_mark: |
 | PWM      |                    | :heavy_check_mark: |
+| PIO      |                    | :heavy_check_mark: |
 
 ## Driver configuration
 
@@ -33,11 +34,11 @@ The default setting is 280 µs, which should work for most cases, but this can b
 Some variants of the WS2812 may have their color components in a different physical or logica