How to read RPMSG messages from M4 to A53 on i.MX 8M Mini

[latorta]

Hi everyone,

I successfully run the echo example on my custom board based on i.MX 8M Mini.

imx_rpmsg_tty module works and I'm able to send some bytes from A53 to M4.

The example anyway should write back the same bytes via the rpmsg_lite_send_nocopy function from M4 to A53.

In fact I find these line with dmesg

[ 3.572174] rpmsg_tty_cb68 65 6c 6c 6f 20 77 6f 72 6c 64 21 hello world!

but if i run this command:

cat /dev/ttyRPMSG

the output is empty.

Of course i can run

echo blabla > /dev/ttyRPMSG

and just like before I find the answer from M4 with dmesg but the cat command gives an empty result.

What's the correct procedure to read the tty?

Thank you!

[joanxie · Accepted solution]

you need to assigns it a file descriptor, writes and reads to int, then closes it, pls refer to the "step 5" 

"https://developer.toradex.com/getting-started/advanced-module-heterogeneous-multicore-processing-hmp..."