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Raspberry Pi FAQ & Troubleshooting

A collection of common issues, error messages, and solutions for Raspberry Pi hardware and software.

Power & Throttling Issues​

Lightning Bolt Icon (Under-voltage)​

This indicates your power supply is dropping below 4.63V.

  • Diagnostics: Run vcgencmd get_throttled to check the status code (see vcgencmd Guide for details).
  • Solution: Use a high-quality 5V/3A power supply and a thick USB cable.

Raspberry Pi 4 USB-C Design Flaw​

Early RPi 4 models have a non-compliant USB-C implementation that prevents them from powering up when using "smart" or E-marked cables (like Apple's USB-C cables).

Networking & Connectivity​

No wlan0 Interface​

If the WiFi interface is missing:

lshw -short
dmesg | grep -i "brcmfmac\|firmware"
sudo modprobe brcmfmac
  • Potential Kernel Bug: For some users, disabling specific features in the Broadcom driver helps:
    /etc/modprobe.d/brcmfmac.conf
    options brcmfmac feature_disable=0x82000
  • Relevant Discussion (GitHub)

Regulatory Database Error​

platform regulatory.0: Direct firmware load for regulatory.db failed with error -2

  • Cause: Missing wireless regulatory database files.
  • Solution (Alpine Linux): apk add wireless-regdb.

brcmfmac: brcmf_set_channel: set chanspec 0x100e fail, reason -52​

Common when trying to set a channel not supported by the current region or hardware. Ensure your country code is set correctly in raspi-config.

System Performance & Stability​

Improving SSH/Entropy Performance​

Raspberry Pi lacks a hardware random number generator in some older models, which can make SSH connection establishment slow.

# Use haveged to generate entropy
apk add haveged
rc-update add haveged
service haveged start

Kernel Hangs: vchiq-keep/0 blocked​

INFO: task vchiq-keep/0:427 blocked for more than 362 seconds.

  • Context: VCHIQ (Video Core Image Queue) is the interface between the ARM CPU and the VideoCore GPU firmware. This often indicates a hang in the GPU firmware or a memory management issue (CMA).
  • Troubleshooting: Try increasing gpu_mem in config.txt or checking for power/voltage issues that might cause the GPU firmware to crash.

Configuration & Peripherals​

Enabling SPI & I2C​

Ensure these are enabled in your hardware configuration:

/boot/config.txt
dtparam=spi=on
dtparam=i2c_arm=on

USB Keyboard Not Working (RPi 4)​

  • Cause: Often caused by insufficient power or USB current limits.
  • Solution: Increase USB current limit (if supported by firmware): 
    echo "max_usb_current=1" | sudo tee -a /boot/config.txt