I'm doing an IoT project. I had a problem related to GPIO pin 14. Even though I solved the problem, now I have questions about pin 14. the question is below.

During booting, relay connected to 14pin become ON and after 1 or 2 seconds it become OFF. The problem is solved now by setting the pin as input and pull-down in dt-blob.bin. One question is come from here, which is that why the same problem is not happened to pin 15 although the default setting of them almost the same and what happen to pin 14 during booting

pin@p14 { function = "uart0";  termination = "no_pulling"; drive_strength_mA = < 8 >; }; // TX uart0
pin@p15 { function = "uart0";  termination = "pull_up";    drive_strength_mA = < 8 >; }; // RX uart0

After a test with an external pull-down circuit, it was discovered that the signal is not related to pull-up or pull-down.

Thanks for reading!


GPIO 14/15 may be used to provide a system console.

GPIO 14 (connected to pin 8) has console output during boot.

GPIO 15 (connected to pin 10) is used for console input.

You can use raspi-config in Raspbian to disable this behaviour.

Interfacing Options -> Serial -> Would you like a login shell to be accessible over serial? No


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  • After setting GPIO pin 14 as default, I tried this, but the same problem was occurred. – 김예성 Sep 2 '19 at 4:10

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