内核版本：3.14.65
CPU：Am335x
1、编译内核：
make menuconfig
Device Drivers ->
<*>SPI support ->
<*>McSPI driver for omap
<*>User mode SPI device driver support
2、添加设备树
bb_spi0_pins: pinmux_bb_spi0_pins {
pinctrl-single,pins = <
0x150 0x30 /* spi0_sclk.spi0_sclk, INPUT_PULLUP | MODE0 */
0x154 0x30 /* spi0_d0.spi0_d0, INPUT_PULLUP | MODE0 */
0x158 0x10 /* spi0_d1.spi0_d1, OUTPUT_PULLUP | MODE0 */
0x15c 0x10 /* spi0_cs0.spi0_cs0, OUTPUT_PULLUP | MODE0 */
>;
};
&spi0 {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&bb_spi0_pins>;
channel@0 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <0>;
spi-max-frequency = <16000000>;
spi-cpha;
};
channel@1 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <1>;
spi-max-frequency = <16000000>;
};
};
编译内核和设备树，下载入开发板。
3、查看SPI是否被注册入Dev中：
ls /dev
console ram8 tty40
cpu_dma_latency ram9 tty41
full random tty42
hwrng root tty43
i2c- rtc0 tty44
input snd tty45
kmem spidev1.0 tty46
kmsg spidev1.1 tty47
log tty tty48
loop-control tty0 tty49
可以看到spidev已经被注册入设备中啦。
3、测试程序的编写：可以借鉴或者直接用Doucment/spi/spi_text.c下的文件。
/*
* 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])) #define WREN 0x06 //set write enable Latch
#define WRDI 0x04 // write disable
#define RDSR 0x05 // read status register
#define WRSR 0x01 // Write Status Register
#define READ 0x03 // Read memory Data
#define WRITE 0x02 // Write memory Data static void pabort(const char *s)
{
perror(s);
abort();
} static const char *device = "/dev/spidev1.0";
static uint8_t mode;
static uint8_t bits = ;
static uint32_t speed = ;
static uint16_t delay; static void transfer_read(int fd)
{
int ret;
uint8_t tx[] = {
0x03, 0x10, 0x00,
}; uint8_t rx[] = {, };
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,
}, {
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = ARRAY_SIZE(rx),
.delay_usecs = delay,
.speed_hz = speed,
.bits_per_word = bits,
},
}; ret = ioctl(fd, SPI_IOC_MESSAGE(), &tr);
if (ret < )
pabort("can't send spi message"); for (ret = ; ret < ARRAY_SIZE(tx); ret++) {
if (!(ret % ))
puts("");
printf("%.5X ", rx[ret]);
}
puts("");
} static void transfer(int fd)
{
int ret;
uint8_t tx[] = {
0x06, 0x02, 0x10, 0x00, 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)] = {, };
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(), &tr);
if (ret < )
pabort("can't send spi message"); for (ret = ; ret < ARRAY_SIZE(tx); ret++) {
if (!(ret % ))
puts("");
printf("%.5X ", 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();
} static void parse_opts(int argc, char *argv[])
{
while () {
static const struct option lopts[] = {
{ "device", , , 'D' },
{ "speed", , , 's' },
{ "delay", , , 'd' },
{ "bpw", , , 'b' },
{ "loop", , , 'l' },
{ "cpha", , , 'H' },
{ "cpol", , , 'O' },
{ "lsb", , , 'L' },
{ "cs-high", , , 'C' },
{ "3wire", , , '' },
{ "no-cs", , , 'N' },
{ "ready", , , 'R' },
{ NULL, , , },
};
int c; c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL); if (c == -)
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 '':
mode |= SPI_3WIRE;
break;
case 'N':
mode |= SPI_NO_CS;
break;
case 'R':
mode |= SPI_READY;
break;
default:
print_usage(argv[]);
break;
}
}
} int main(int argc, char *argv[])
{
int ret = ;
int fd; parse_opts(argc, argv); fd = open(device, O_RDWR);
if (fd < )
pabort("can't open device"); //mode = mode | 0 | SPI_LSB_FIRST; /*
* spi mode
*/
ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
if (ret == -)
pabort("can't set spi mode"); ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
if (ret == -)
pabort("can't get spi mode"); /*
* bits per word
*/
ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
if (ret == -)
pabort("can't set bits per word"); ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
if (ret == -)
pabort("can't get bits per word"); /*
* max speed hz
*/
ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
if (ret == -)
pabort("can't set max speed hz"); ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
if (ret == -)
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/); //transfer(fd); while()
{
//transfer(fd);
transfer_read(fd);
//write(fd,buf_me,1);
} close(fd); return ret;
}
需要注意:
是内核中SPI的数据发送和接收都是以byte为单位的。所以假如设置per_bits_word不是8or16or32时用上面的程序会出错的。假如设置的per_bits_word为9（https://blog.****.net/yasin_lee/article/details/54632982），那么在设置
struct spi_ioc_transfer tr 这个结构体时.len的长度一定要注意了。因为驱动在判断per_bits_word>8时，会用两个字节来存放要发送的数据的，大于16就会用4个字节来存放要发送的数据。
.len = ARRAY_SIZE(tx),ARRAY_SIZE只能计算tx数组的的元素的个数，并不会计算tx数组所占的字节数。所以当per_bits_word%8 > 时（也就是非8的整数倍），若是还用.len = ARRAY_SIZE(tx)
来计算SPI发送数据的长度，会引起内核崩溃的。 可以用以下方法来计算长度：
.len = sizeof(tx)，
.len = ARRAY_SIZE(tx)*2//（16>per_bits_word>8）
.len = ARRAY_SIZE(tx)*4//(32>per_bits_word>16) 根据测试在用这个函数发送数据时：
ioctl(fd, SPI_IOC_MESSAGE(1), &tr)
每配置一个 struct spi_ioc_transfer tr 结构体就相当于拉低一次CS，当然前提是配置CS低有效。
也就是SPI每发送一个SPI_IOC_MESSAGE,CS被拉低一次，可以通过这个来编写不同的SPI的接口芯片访问方式（暂时是这样理解的，等spi芯片到了，可以测试一下）。 还有就是此版本的SPI驱动并不支持低字节优先发送，假如设置了低字节优先发送的模式，会报以下错误：
spidev spi1.: setup: unsupported mode bits
can't set spi mode: Invalid argument
Aborted
可以从内核源码中了解相关信息：linux-3.14.65/drivers/spi/spi.c
* Note that this call will fail if the protocol driver specifies an option
* that the underlying controller or its driver does not support. For
* example, not all hardware supports wire transfers using nine bit words,
* LSB-first wire encoding, or active-high chipselects.
*/
int spi_setup(struct spi_device *spi)
{
unsigned bad_bits, ugly_bits;
int status = ;
若是没有SPI芯片可以用来测试的话，可已将AM335x的Tx与Rx脚短接，这样也可以测试驱动及驱动测试程序的好坏。