Problem with writing rpmsg from Linux app

Technical Support
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1

Hello,

I am starting to work with Cortex-M4 of the iMX7, sending and receiving RPMsg and I was wondering If I could get any tip on what I am doing wrong, here it is what I am doing:

On Cortex-M4:

Following these articles:

I was able to get running the str_echo_freertos example

In Linux side:

I was able to send and recieve message with the following:

root@b2qt-colibri-imx7-emmc:~# modprobe imx_rpmsg_tty
[   20.817876] imx_rpmsg_tty virtio0.rpmsg-openamp-demo-channel.-1.0: new channel: 0x400 -> 0x0!
[   20.826821] Install rpmsg tty driver!
root@b2qt-colibri-imx7-emmc:~# stty -F /dev/ttyRPMSG0 -echo  && exec 3<> /dev/ttyRPMSG0
root@b2qt-colibri-imx7-emmc:~# echo Test from command line >&3
root@b2qt-colibri-imx7-emmc:~# cat <&3
Test from command line

^C
root@b2qt-colibri-imx7-emmc:~#

And now, I created a simple C program that could send and receive messages, but is not working properly, here it is:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <termios.h>

#define TTY_RPMSG "/dev/ttyRPMSG0"

int main(int argc, char *argv[])
{
	int fd, len;
	struct termios tty_settings;
	char buf[100] = {0};

	if (argv[1] == NULL)
	{
		printf("error: needs to specify a message to send\n");
		return EXIT_FAILURE;
	}

	printf("Start '%s'\r\n", __TIME__);

	fd = open(TTY_RPMSG, O_RDWR | O_NOCTTY | O_SYNC | O_NDELAY);
	if(fd < 0)
	{
		printf("error: port could not be opened '%s'\n", TTY_RPMSG);
		return EXIT_FAILURE;
	}

	/* Get the current attributes of the Serial port */
	tcgetattr(fd, &tty_settings);

	/* Set raw mode */
	cfmakeraw(&tty_settings);    
	tcsetattr(fd, TCSANOW, &tty_settings);

	printf("to write: '%s'\n", argv[1]);
    /* Original line that was getting the wrong length of argv[1] */
	/* write(fd, argv[1], sizeof(argv[1])); */
    /* Getting the correct length with strlen */
	write(fd, argv[1], strlen(argv[1]));
	tcdrain(fd);
    /* Sleep not needed */
	/* sleep(1); */

	while (1)
	{
		len = read(fd, buf, sizeof(buf));
		if (len > 0)
		{
			buf[len] = 0;
			printf("received:\r\n");
			printf("    len = %d\r\n", len);
			printf("    buf = %s\r\n\r\n", buf);
			fflush(stdout);
		}	
	}
	close(fd); 

	return EXIT_SUCCESS;
}

I compile, run my code and I get this:

root@b2qt-colibri-imx7-emmc:~# modprobe imx_rpmsg_tty
[   36.076102] imx_rpmsg_tty virtio0.rpmsg-openamp-demo-channel.-1.0: new channel: 0x400 -> 0x0!
[   36.084932] Install rpmsg tty driver!
root@b2qt-colibri-imx7-emmc:~# ./send_rpmsg_linux_g 1234567890
Start '15:58:05'
to write: '1234567890'
received:
    len = 4
    buf = 1234

^C
root@b2qt-colibri-imx7-emmc:~#

It looks like the full message was not sent.

From the output of the Cortex-M4 terminal:

RPMSG String Echo FreeRTOS RTOS API Demo...
RPMSG Init as Remote
Name service handshake is done, M4 has setup a rpmsg channel [0 ---> 1024]
Get Message From Master Side : "1234" [len : 4]

Any tip on how to get the full message sent?

Thanks

2

I found what was wrong:

I am getting the argv[1] length wrong, (facepalm)

At line 41, in the write I’ve changed to strlen and it works fine:

    ...
	write(fd, argv[1], strlen(argv[1]));
	tcdrain(fd);
    ...

Sorry

3

Perfect that you found a solution. Thanks for the feedback.