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P2040: How to send/receive data on second UART

Question asked by gourav jain on Nov 22, 2018
Latest reply on Dec 20, 2018 by Pavel Chubakov

Hi All,

P2040 do support 4 UARTs. Out of 4 i'm using two, UART0 and UART1.

Both UARTs are working as a console dev in standalone case.

by changing followings,

1) RCW value.

2) CONFIG_CONS_INDEX  1 or 2 in the /include/configs/P2041RDB.h file in the u-boot source.

3) root=/dev/ram rw console=ttyS0,115200 or root=/dev/ram rw console=ttyS1,115200


Till here everything is fine.

But when i tried to make UART1 as a console and UART0 just to send/receive normal data, UART1 is working properly while no transaction in UART0.

Wrote a small application for sending data in UART0,




char data[] = "aa";
int fd, i;
fd = open("/dev/ttyS0", O_RDWR);
if(fd <0)


for (i=0; i<10; i++){
         write(data, sizeof(data), 1, fd);


Expected data on UART0 terminal(rs-232), But not coming.

Would be very thankful if someone help me out.