Raspberry Pi

General Pi

Pinouts

Lets talk Pi pinout and HATS all very important. There is a great resource that says it way better here

i2c non root

Add user to i2c group and create udev rule /etc/udev/rules.d/50-i2c.rules

SUBSYSTEM=="i2c-dev", GROUP="i2c", MODE="0660"

Hangs On Boot

If the rpi is hanging on boot with the message random: crng init done.

If running Pi headless at boot the kernel waits for mouse movements to initialize the random number generator.

Install and start haveged to solve this.

sudo apt -y install haveged
sudo systemctl enable haveged

Manage WiFi

Check that the WiFi antenna isn't blocked.

sudo rfkill list all

To unblock your antenna use.

sudo rfkill unblock 0

wpa_supplicant

First kill all wpa_supplicant workers and then test your configuration file for errors.

Basic wpa_supplicant template /etc/wpa_supplicant/wpa_supplicant.conf

ctrl_interface=/var/run/wpa_supplicant GROUP=netdev
country=CA
update_config=1

network={
  scan_ssid=1
  ssid=""
  psk=""
}

sudo killall wpa_supplicant

Add -d flag on the end to make it more verbose

sudo wpa_supplicant -c/etc/wpa_supplicant/wpa_supplicant.conf -iwlan0

Pi4

USB Boot Issues

Some firmware in external USB enclosures can cause problems with booting. First step to resolving these issues is to install Raspberry Pi OS on a Micro SD card, boot, and sudo apt update & sudo apt -y full-upgrade. Any firmware upgrades will be performed by rpi-eeprom-update service and applied after next reboot. More information can be found at boot eeprom documentation.

usb-storage.quirks

Booted from your SD card without your external USB enclosure connected run sudo dmesg -C, now plug in the device and run sudo dmesg. The idVendor and idProduct are the two hexadecimal values you require.

Add these two values to the beginning of your /boot/cmdline.txt with usb-storage.quirks.

usb-storage.quirks=aaaa:bbbb:u <-- You must add the :u following your two values.

Reboot the system and check that quirks have been applied.

dmesg | grep usb-storage

Bootloader and Conditional Filters

Bootloader Config

You can find the docs here.

Conditional Filters

You can find the docs here.