Some UART configuration parameters are not accepted (Colibri VF50 / linux)

Technical Support
, , ,
1

On the Colibri VF50 board, it is not possible to configure the UART for two stop bits.

# stty -F /dev/ttyLP2 9600 cs8 cstopb
stty: /dev/ttyLP2: cannot perform all requested operations

It is also not possible to configure the UART with 7 data bits and no parity bits.

# stty -F /dev/ttyLP2 9600 cs7 -parenb -parodd
stty: /dev/ttyLP2: cannot perform all requested operations

The same problems occur when using the C tcsetattr function instead of the stty command.

2

Hi @mdoreille and Welcome to the Toradex Community!

Could you provide the version of the hardware (including carrier board) and software of your module?

What is your application? What are you trying to do?

Best regards,
Jaski

3

The carrier board is a custom board.

The software is buildroot version 2017.02.2.
The linux kernel version is 4.4.59.

The DMA is activated for UART.

The software is a serial to TCP data forwarder that already works on other boards (ARM7).
It can accept any UART configurations from the TCP link.

Some specifics configurations don’t work on the Colibri V50. For example 7 data bits without parity bit for any baudrate. Or any configuration with 2 stop bits.

Best Regards,
Mathias

4

Looking at the VFxxx controller reference manual, and looking at the linux driver sources, it is simply a limitation of the UART that does not support 7 data bits without parity as well as 2 stop bits.

Thanks,
Mathias

5

Thanks for your Input.

Best regards,
Jaski