Day09 - GPIO LED Driver

Objective

Control LED via kernel driver using gpiod

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Step 1 - Build Module

make

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Step 2 - Build Device Tree Overlay

dtc -@ -I dts -O dtb -o mygpio-led.dtbo mygpio-led-overlay.dts

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Step 3 - Load Driver

sudo insmod mygpio.ko
sudo dtoverlay mygpio-led

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Step 4 - Verify

ls -l /dev/mygpio
dmesg | grep mygpio

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Step 5 - Test

echo 1 | sudo tee /dev/mygpio
echo 0 | sudo tee /dev/mygpio
cat /dev/mygpio

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Expected Result

• LED ON/OFF
• read returns correct state

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Troubleshooting

• Check dmesg
• Ensure overlay loaded
• Ensure GPIO not used by others

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