diff --git a/libraries/AP_HAL_ChibiOS/hwdef/CUAVv5/README.md b/libraries/AP_HAL_ChibiOS/hwdef/CUAVv5/README.md
index a45e6cb105..af6b76e479 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/CUAVv5/README.md
+++ b/libraries/AP_HAL_ChibiOS/hwdef/CUAVv5/README.md
@@ -55,7 +55,7 @@ The CUAVv5 supports up to 14 PWM outputs. First first 8 outputs (labelled
 outputs support all PWM output formats, but not DShot.
 
 The remaining 6 outputs (labelled AUX1 to AUX6) are the "auxillary"
-outputs. These are directly attached to the STM32F427 and support all
+outputs. These are directly attached to the STM32F765 and support all
 PWM protocols as well as DShot.
 
 All 14 PWM outputs have GND on the top row, 5V on the middle row and
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/README.md b/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/README.md
new file mode 100644
index 0000000000..4d39ce596d
--- /dev/null
+++ b/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/README.md
@@ -0,0 +1,125 @@
+# Pixhawk4 Flight Controller
+
+The Pixhawk4 flight controller is sold by [Holybro](http://www.holybro.com/product/55)
+
+## Features
+
+ - STM32F765 microcontroller
+ - Two IMUs: ICM20689 and BMI055
+ - MS5611 SPI barometer
+ - builtin SPI IST8310 magnetometer
+ - microSD card slot
+ - 6 UARTs plus USB
+ - 14 PWM outputs
+ - Four I2C and two CAN ports
+ - External Buzzer
+ - external safety Switch
+ - voltage monitoring for servo rail and Vcc
+ - two dedicated power input ports for external power bricks
+
+## Pinout
+
+![Pixhawk4 Board](pixhawk4-pinout.jpg "Pixhawk4")
+
+## UART Mapping
+
+ - SERIAL0 -> USB
+ - SERIAL1 -> UART2 (Telem1)
+ - SERIAL2 -> UART3 (Telem2)
+ - SERIAL3 -> UART1 (GPS)
+ - SERIAL4 -> UART4 (GPS2)
+ - SERIAL5 -> UART6 (spare)
+ - SERIAL6 -> UART7 (spare, debug)
+
+The Telem1 and Telem2 ports have RTS/CTS pins, the other UARTs do not
+have RTS/CTS.
+
+The UART7 connector is labelled debug, but is available as a general
+purpose UART with ArduPilot.
+
+## RC Input
+ 
+RC input is configured on the port marked DSM/SBUS RC. This connector
+supports all RC protocols. Two cables are available for this port. To
+use software binding of Spektrum satellite receivers you need to use
+the Spektrum satellite cable.
+
+## PWM Output
+
+The Pixhawk4 supports up to 14 PWM outputs. First first 8 outputs (labelled
+"MAIN") are controlled by a dedicated STM32F100 IO controller. These 8
+outputs support all PWM output formats, but not DShot.
+
+The remaining 6 outputs (labelled AUX1 to AUX6) are the "auxillary"
+outputs. These are directly attached to the STM32F765 and support all
+PWM protocols as well as DShot.
+
+The 8 main PWM outputs are in 3 groups:
+
+ - PWM 1 and 2 in group1
+ - PWM 3 and 4 in group2
+ - PWM 5, 6, 7 and 8 in group3
+
+The 6 auxillary PWM outputs are in 2 groups:
+
+ - PWM 1, 2, 3 and 4 in group1
+ - PWM 5 and 6 in group2
+
+Channels within the same group need to use the same output rate. If
+any channel in a group uses DShot then all channels in the group need
+to use DShot.
+
+## Battery Monitoring
+
+The board has two dedicated power monitor ports on 6 pin
+connectors. The correct battery setting parameters are dependent on
+the type of power brick which is connected.
+
+## Compass
+
+The Pixhawk4 has a builtin IST8310 compass. Due to potential
+interference the board is usually used with an external I2C compass as
+part of a GPS/Compass combination.
+
+## GPIOs
+
+The 6 PWM ports can be used as GPIOs (relays, buttons, RPM etc). To
+use them you need to limit the number of these pins that is used for
+PWM by setting the BRD_PWM_COUNT to a number less than 6. For example
+if you set BRD_PWM_COUNT to 4 then PWM5 and PWM6 will be available for
+use as GPIOs.
+
+The numbering of the GPIOs for PIN variables in ArduPilot is:
+
+ - AUX1 50
+ - AUX2 51
+ - AUX3 52
+ - AUX4 53
+ - AUX5 54
+ - AUX6 55
+
+## Analog inputs
+
+The Pixhawk4 has 7 analog inputs
+
+ - ADC Pin0 -> Battery Voltage
+ - ADC Pin1 -> Battery Current Sensor
+ - ADC Pin2 -> Battery Voltage 2
+ - ADC Pin3 -> Battery Current Sensor 2
+ - ADC Pin4 -> ADC port pin 2
+ - ADC Pin14 -> ADC port pin 3
+ - ADC Pin10 -> ADC 5V Sense
+ - ADC Pin11 -> ADC 3.3V Sense
+ - ADC Pin103 -> RSSI voltage monitoring
+
+## Loading Firmware
+
+The board comes pre-installed with an ArduPilot compatible bootloader,
+allowing the loading of *.apj firmware files with any ArduPilot
+compatible ground station.
+
+## Acknowledgements
+
+Thanks to
+[PX4](https://docs.px4.io/en/flight_controller/pixhawk4.html) for
+images used under the [CC-BY 4.0 license](https://creativecommons.org/licenses/by/4.0/)
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/pixhawk4-pinout.jpg b/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/pixhawk4-pinout.jpg
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