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I have a board running linux and it doesn't boot when connecting a specific hardware, the board doesn't even load the kernel so i have to use a serial cable to see what's causing the issue, currently i don't have a serial to usb converter so i would like to know if i can use the raspberry pi instead, i've used an arduino board as converter before and was wondering if this is possible with a raspberry pi basically i would like to connect Tx and Rx to the board and use a program like minicom inside the raspberry to watch the boot sequence.

UPDATE: I'm using raspberry pi 3 model B running raspbian jessie

uname -a : Linux raspberrypi 4.4.50-v7+ #970 SMP Mon Feb 20 19:18:29 GMT 2017 armv7l GNU/Linux

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  • No problem provided 1) the other system uses 3V3 TTL on its TX line, 2) you set the correct baud rate on the Pi, and 3) the other system is configured to output on TX during boot.
    – joan
    Commented Mar 12, 2017 at 5:26

1 Answer 1

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In general, no - this is possible but not simple. The hardware UART on the Pi is usually used as a boot console (to help in debugging random crashes during boot, etc.) In order to use to UART as a general purpose device, you need to disable this.

If you want to change the console UART, you need to edit (as root) /boot/cmdline.txt.

Then delete console=ttyAMA0,115200 and kgdboc=ttyAMA0,115200

Also edit /etc/inittab and comment out the line like T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

Bear in mind that the I/O is 3.3v, so it will be fine for connecting directly to another mcu, but not to a RS232 port.

More details here

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  • cmdline.txt doesn't have console=ttyAMA0,115200 but it has console=serial0,115200 which i deleted, also since raspbian no longer uses inittab i used systemctl to disable serial service but found that it was already disabled, after reboot tried to use minicom with ttyAMA0 but couldn't get any data, tried to short the TX and Rx but i'm not getting loop back either
    – MOHAMMAD RASIM
    Commented Mar 11, 2017 at 19:22

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