config.txt

[pi4]
#########
# uart configuration
#
# uart  hardware  path         connector  tx             rx
# 1     mini      /dev/ttyS0   Serial 1   GPIO14 PIN 8   GPIO15 PIN 10
# 3     pl011     /dev/ttyAMA1 Serial 3   GPIO4  PIN 7   GPIO5  PIN 29
# 4     pl011     /dev/ttyAMA2 Serial 4   GPIO8  PIN 24  GPIO9  PIN 21
# 5     pl011     /dev/ttyAMA3 Serial 5   GPIO12 PIN 32  GPIO13 PIN 33

# enable the uart1 dtoverlay to be applied
# this fixes the videocore frequency on raspberry pi 4 to 500MHz
# this is because the uart1 clock is derived from videocore clock
enable_uart=1

dtoverlay=uart1
dtoverlay=uart3
dtoverlay=uart4
dtoverlay=uart5

#########
# i2c configuration
#
# i2c0 - internal bus
# SCL0 GPIO1 PIN 28
# SDA0 GPIO0 PIN 27
# CAT24C32 @ 0x50
#
# i2c1 - internal bus
# SCL1 GPIO3 PIN 5
# SDA1 GPIO2 PIN 3
# AK09915 @ 0x0C
# MMC5883 @ 0x30
# ADS1115 @ 0x48
#
# i2c4 - internal bus
# SCL4 GPIO7 PIN 26
# SDA4 GPIO6 PIN 31
# PCA9685 @ 0x40
# BMP280  @ 0x76
#
# i2c6 - external bus for i2c connectors
# SCL6 GPIO23 PIN 16
# SDA6 GPIO22 PIN 15
#
# NOTE: the i2c-dev kernel module needs to be loaded for the i2c bus to be accessible under
# /dev/i2c-*
# `sudo modprobe i2c-dev` or add `i2c-dev` to /etc/modules-load.d/modules.conf

# enable i2c0 mux
# after kernel 5, i2c0 is muxed between the camera/dsi i2c bus on GPIO 44/45
# and the i2c bus on GPIO 0/1
# this creates 3 devices: i2c-0, i2c-10, and i2c-11
# i2c-0: the i2c bus on the header pins (GPIO 0/1)
# i2c-10: the i2c bus on the camera/dsi pins (GPIO 44/45)
# i2c-11: the parent i2c device/mux. accessing this device uses whichever of the child devices was accessed
# do not use this in combination with dtoverlay=i2c0, or with dtparam=i2c_arm=on
dtparam=i2c_vc=on

dtoverlay=i2c1
dtoverlay=i2c4,pins_6_7
dtoverlay=i2c6,pins_22_23

#########
# spi configuration

dtparam=spi=on

# spi0 bus specially set up to drive neopixel rgb led
# MOSI0 GPIO10 PIN 19 neopixel DIN /dev/spi0.0
dtoverlay=spi0-led

# spi1 bus with 3 chip selects
# MOSI1 GPIO20 PIN 38
# MISO1 GPIO19 PIN 35
# SCLK1 GPIO21 PIN 40
# CS0   GPIO18 PIN 12 not connected
# CS1   GPIO17 PIN 11 not connected
# CS2   GPIO16 PIN 36 ICM20602 /dev/spi1.2
dtoverlay=spi1-3cs

#########
# gpio configuration

# User LEDs - output drive high
# LED1 GPIO24 PIN 18
# LED2 GPIO25 PIN 22
# LED3 GPIO11 PIN 23
gpio=11,24,25=op,pu,dh

# PWM output enable gpio 37 output drive low
gpio=37=op,pd,dl