TEST PI

A Raspberry Pi Hat for testing embedded Linux boards.

Key features:

• Well visible 23mm LEDs, red & green
• Buzzer
• One-Wire interface
• 3.3V UART interface (same pin-out as the FTDI UART cable)
• 2 Grove connectors with 2 digital outputs each
• EEPROM to store the hat-id

You may find this HAT useful in embedded Linux flash- or test stations. Connect up to 4 relays to control the board power and boot pins.

Installation

Compile the device tree overlay

dtc -@ -I dts -O dtb -o test_pi_overlay.dtbo test_pi_overlay.dts

Install the device tree overlay

sudo mv test_pi_overlay.dtbo /boot/overlays/

Edit /boot/config.txt to load the overlay at boot:

dtoverlay=test_pi_overlay

Reboot the Raspberry Pi:

sudo reboot

Testing the Features

Check One-Wire:

ls /sys/bus/w1/devices/

If you have a 1-Wire device (e.g., DS18B20 sensor), it should appear here.

Check UART:

ls -l /dev/serial*

It should show /dev/serial0 mapped to ttyS0.

Toggle Buzzer Output:

cho "1" > /sys/class/gpio/gpio17/value  # Turn GPIO17 ON
echo "0" > /sys/class/gpio/gpio17/value  # Turn GPIO17 OFF

Toogle LED Outputs:

cho "1" > /sys/class/gpio/gpio17/value  # Turn GPIO17 ON
echo "0" > /sys/class/gpio/gpio17/value  # Turn GPIO17 OFF

Toggle Digital Outputs:

cho "1" > /sys/class/gpio/gpio17/value  # Turn GPIO17 ON
echo "0" > /sys/class/gpio/gpio17/value  # Turn GPIO17 OFF