Getting ttyS1 working in cyclone v


I am using DE0 Nano with Cyclone V SoC and Angstrom running on HPS.

I have enabled the UART1 in Qsys with FPGA option, and then routed the Tx and Rx to GPIO_0 pins 0 and 1.
I have verified in ‘/etc/systemd/system’ that getty is being used with ‘ttyS0’.
However any write to ‘/dev/ttyS1’ provides nothing on the GPIO pins. (verified with oscilloscope)
For example echo 0xFF > /dev/ttyS1

Also echo 0xFF > /dev/ttyS0 produces an output 0XFF on the console. .

Does anyone know what can be the issue here?


have You also updated a preloader? The preloader sets peripherals of the processor at booting time, so it also makes UART1 (and other things set up at Qsys) ready to function in a point of view of hardware. As far as You have not done it yet, it should help You. Try to look at:
Best regards…


Yes. the preloader was updated. Actually the issue was with the mapping to the GPIO pins. I had incorrectly mapped a variable to the GPIO pin and hence it was never actually receiving anything from the UART;