UART on my pi cannot send data, I can receive data from another machine, but I cannot send any data using the 'tx' pin of UART. I also try to connect 'tx' and 'rx' on my pi, but still no data is sent or received.
I think it's a software problem, because I tried to burn a fresh image of Raspbean to my SD card, UART works fine. But with my existing system image, it cannot send data. I have made a lot of changes on my current system and want to keep it, but I don't know what I should do to make UART work correctly.
I have followed this blog, and still does not work. http://www.irrational.net/2012/04/19/using-the-raspberry-pis-serial-port/
I have run gpiotest from here http://abyz.me.uk/rpi/pigpio/examples.html#Shell_code
And the result is good as shown below.
Skipped non-user gpios: 0 1 28 29 30 31 Tested user gpios: 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Failed user gpios: None