For TX/RX pins, I think that you mainly need to set the two pins to mode1. Once that is done, those pins are under the control of the Uart.
Have you tried using MRAA to init it. You should be able to call: mraa_uart_init(0);
With the context you can call: mraa_uart_get_dev_path
Which should give you the path name and the like for the device that you can then open and then use termios control to setup the uart... I do some of this in my projects, although mostly I have been using USB devices for uarts...
Thank you for your answer
Indeed using MRAA was my first try for UART communication, together with termios
After retrieving the path with mraa_uart_init and mraa_uart_get_dev_path, TX and RX stay at low level which make me think of an issue with my config (UART being usually based on an idle high level)
Opening and writing did not result in any activity on the pins, that's why I tried several configurations using a terminal
I am currently thinking about a possible hardware problem with the level shifter on the GPIO breakout board, I will provide an update if I can find where it does come from !
I would also double check your wiring, and check voltages. Not sure which Sparkfun one you have example: (https://www.sparkfun.com/products/11771)
Need to make sure both Vcca and Vccb are hooked up. One with 1.8v and the other with 3.3 or ... And make sure both grounds are hooked up.
Thank you for this advice KurtE,
I have checked that power supply (1.8V & 3.3V) and ground are properly connected.
Interestingly the issue is only for the TX pin, all other pins have a proper voltage shifting
I may have made a mistake on my first wiring which led to drive more than the 50 mA limitation of the TXB0108 on the board