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RPi3B first serial port (PL011 ttyAMA0) Rx not working?

Posted: Wed Dec 05, 2018 7:41 am
by rpi3user
Hello all,

I've got an issue with my RPi3B and the PL011 ttyAMA0 serial port.

This port is normally mapped to the Bluetooth chip. When I move the PL011 ttyAMA0 port to the GPIO headers via the DT Overlay (either disable-bt or bt-miniuart), I get proper serial output from the RPi on the attached PC using a terminal program. However, typing characters in the terminal program of the PC does not produce anything received on the RPi side. The scenario is the same for the U-Boot bootloader and Linux (Raspbian Jessie).

However, removing the DT Overlays and adding enable_uart=1 to config.txt makes U-Boot and Linux use the MiniUART (ttyS0) and everything works fine, so the PC terminal program and its USB-to-serial-dongle (3.3V) can be ruled out.

I am using latest firmware from the foundation's web site.

Anyone else has seen similar issues? I suspect an issue with the mapping of the Rx Pin to the PL011 in the DT Overlays but I am unable to dig into this deeper.