rc_uart_loopback.c

/**
 * @file rc_uart_loopback.c
 * @example    rc_uart_loopback
 *
 * This is a test to check read and write operation of UART buses. For this
 * example to work, connect the RX and TX wires of one of the included 4-pin
 * JST-SH pigtails and plug into the UART1 or UART5 headers. You may also elect
 * to test UART0 on the debug header or UART2 on the GPS header. The test
 * strings this programs transmits will then loopback to the RX channel.
 */

#include <stdio.h>
#include <stdlib.h> // for atoi
#include <string.h>
#include <rc/uart.h>

#define BUF_SIZE        32
#define TIMEOUT_S       0.5
#define BAUDRATE        115200

static void __print_usage(void)
{
        printf("\n");
        printf("Usage: rc_uart_loopback {bus}\n");
        printf("This sends a short message out the specified bus and then\n");
        printf("reads it back in. This requires connecting RX to TX to make a loopback.\n");
        printf("For Robotics Cape or BeagleBone Blue specify bus 0,1,2 or 5\n");
        printf("\n");
        return;
}

int main(int argc, char *argv[])
{
        char* test_str = "Hello World";
        int bytes = strlen(test_str); // get number of bytes in test string
        uint8_t buf[BUF_SIZE];
        int ret; // return value
        int bus; // which bus to use

        // Parse arguments
        if(argc!=2){ //argc==2 actually means one argument given
                __print_usage();
                return -1;
        }
        else bus = atoi(argv[1]);

        if(!(bus==0||bus==1||bus==2||bus==5)){
                __print_usage();
                return -1;
        }

        printf("\ntesting UART bus %d\n\n", bus);
        // disable canonical (0), 1 stop bit (1), disable parity (0)
        if(rc_uart_init(bus, BAUDRATE, TIMEOUT_S, 0,1,0)){
                printf("Failed to rc_uart_init%d\n", bus);
                return -1;
        }

        // Flush and Write
        printf("Sending  %d bytes: %s \n", bytes, test_str);
        rc_uart_flush(bus);
        rc_uart_write(bus, (uint8_t*)test_str, bytes);

        // Read
        printf("reading bytes:\n");
        memset(buf,0,sizeof(buf));
        ret = rc_uart_read_bytes(bus, buf, bytes);
        if(ret<0) fprintf(stderr,"Error reading bus\n");
        else if(ret==0) printf("timeout reached, %d bytes read\n", ret);
        else printf("Received %d bytes: %s \n", ret, buf);

        // now write again
        printf("\n");
        printf("Sending  %d bytes: %s \n", bytes, test_str);
        rc_uart_write(bus, (uint8_t*)test_str, bytes);

        // read back as line
        printf("reading line:\n");
        memset(buf,0,sizeof(buf));
        ret = rc_uart_read_line(bus, buf, sizeof(buf));
        if(ret<0) fprintf(stderr,"Error reading bus\n");
        else if(ret==0) printf("timeout reached, %d bytes read\n", ret);
        else printf("Received %d bytes: %s \n", ret, buf);

        // close
        rc_uart_close(bus);
        return 0;
}