Hi Shane,
I have used a code originally written for RasPi for loobpack test:
/*
* SPI testing utility (using spidev driver)
*
* Copyright (c) 2007 MontaVista Software, Inc.
* Copyright (c) 2007 Anton Vorontsov <avorontsov@ru.mvista.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License.
*
* Cross-compile with cross-gcc -I/path/to/cross-kernel/include
*/
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
static void pabort(const char *s)
{
perror(s);
abort();
}
static const char *device = "/dev/spidev1.1";
static uint8_t mode;
static uint8_t bits = 8;
static uint32_t speed = 500000;
static uint16_t delay;
static void transfer(int fd)
{
int ret;
uint8_t tx[] = {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x40, 0x00, 0x00, 0x00, 0x00, 0x95,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xDE, 0xAD, 0xBE, 0xEF, 0xBA, 0xAD,
0xF0, 0x0D,
};
uint8_t rx[ARRAY_SIZE(tx)] = {0, };
struct spi_ioc_transfer tr = {
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = ARRAY_SIZE(tx),
.delay_usecs = delay,
.speed_hz = speed,
.bits_per_word = bits,
};
ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
if (ret < 1)
pabort("can't send spi message");
for (ret = 0; ret < ARRAY_SIZE(tx); ret++) {
if (!(ret % 6))
puts("");
printf("%.2X ", rx[ret]);
}
puts("");
}
static void print_usage(const char *prog)
{
printf("Usage: %s [-DsbdlHOLC3]\n", prog);
puts(" -D --device device to use (default /dev/spidev1.1)\n"
" -s --speed max speed (Hz)\n"
" -d --delay delay (usec)\n"
" -b --bpw bits per word \n"
" -l --loop loopback\n"
" -H --cpha clock phase\n"
" -O --cpol clock polarity\n"
" -L --lsb least significant bit first\n"
" -C --cs-high chip select active high\n"
" -3 --3wire SI/SO signals shared\n");
exit(1);
}
static void parse_opts(int argc, char *argv[])
{
while (1) {
static const struct option lopts[] = {
{ "device", 1, 0, 'D' },
{ "speed", 1, 0, 's' },
{ "delay", 1, 0, 'd' },
{ "bpw", 1, 0, 'b' },
{ "loop", 0, 0, 'l' },
{ "cpha", 0, 0, 'H' },
{ "cpol", 0, 0, 'O' },
{ "lsb", 0, 0, 'L' },
{ "cs-high", 0, 0, 'C' },
{ "3wire", 0, 0, '3' },
{ "no-cs", 0, 0, 'N' },
{ "ready", 0, 0, 'R' },
{ NULL, 0, 0, 0 },
};
int c;
c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
if (c == -1)
break;
switch (c) {
case 'D':
device = optarg;
break;
case 's':
speed = atoi(optarg);
break;
case 'd':
delay = atoi(optarg);
break;
case 'b':
bits = atoi(optarg);
break;
case 'l':
mode |= SPI_LOOP;
break;
case 'H':
mode |= SPI_CPHA;
break;
case 'O':
mode |= SPI_CPOL;
break;
case 'L':
mode |= SPI_LSB_FIRST;
break;
case 'C':
mode |= SPI_CS_HIGH;
break;
case '3':
mode |= SPI_3WIRE;
break;
case 'N':
mode |= SPI_NO_CS;
break;
case 'R':
mode |= SPI_READY;
break;
default:
print_usage(argv[0]);
break;
}
}
}
int main(int argc, char *argv[])
{
int ret = 0;
int fd;
parse_opts(argc, argv);
fd = open(device, O_RDWR);
if (fd < 0)
pabort("can't open device");
/*
* spi mode
*/
ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
if (ret == -1)
pabort("can't set spi mode");
ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
if (ret == -1)
pabort("can't get spi mode");
/*
* bits per word
*/
ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
if (ret == -1)
pabort("can't set bits per word");
ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
if (ret == -1)
pabort("can't get bits per word");
/*
* max speed hz
*/
ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
if (ret == -1)
pabort("can't set max speed hz");
ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
if (ret == -1)
pabort("can't get max speed hz");
printf("spi mode: %d\n", mode);
printf("bits per word: %d\n", bits);
printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);
transfer(fd);
close(fd);
return ret;
}
Source: RASPBERRY PI SPI LOOPBACK TESTING
From my understanding of the code this should work fine on Xavier NX or indeed on any dev board with spi interface.
I have compiled the code as per the instructions on the website:
$ gcc -o spidev_test spidev_test.c
Then I have executed the code using the same instruction as in the tutorial:
$ ./spidev_test -D /dev/spidev0.0
And the results are:
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF
Which from the documentation of this little useful program would mean that the SPI interface is indeed working correctly? Unless (and this is where my knowledge is still lacking) getting FF or 00 throughout means that it is not.
I have tested this on RasPi just to make sure it works, and the result is as bove but with 00 not FF.
EDIT:
Update, I had the wrong pins shorted :facepalm: , now my results are:
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)
FF FF FF FF FF FF
40 00 00 00 00 95
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
DE AD BE EF BA AD
F0 0D
Which confirms that the SPI is indeed working.