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Here is a very simple demo application that shows how to read the Flash ID from an SPI Flash device:

/*

* Sample application that makes use of the SPIDEV interface * to access an SPI slave device. Specifically, this sample * reads a Device ID of a JEDEC-compliant SPI Flash device. */ #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <linux/types.h> #include <linux/spi/spidev.h> #include <stdint.h> #include <stdio.h> #include <string.h> #include <errno.h> int main(int argc, char **argv) { /*

* This assumes that a 'mdev -s' has been run to create

* /dev/spidev* devices after the kernel bootstrap.

* First number is the "bus" (SPI contoller id), second number

* is the "chip select" of the specific SPI slave

* ...

* char *name = "/dev/spidev1.1";

*/

char *name;

int fd;

struct spi_ioc_transfer xfer[2];

unsigned char buf[32], *bp;

int len, status;

name = argv[1];

fd = open(name, O_RDWR);

if (fd < 0) {

perror("open");

return 1;

}

memset(xfer, 0, sizeof xfer);

memset(buf, 0, sizeof buf);

len = sizeof buf;

/*

* Send a GetID command

*/

buf[0] = 0x9f;

len = 6;

xfer[0].tx_buf = (unsigned long)buf;

xfer[0].len = 1;

xfer[1].rx_buf = (unsigned long) buf;

xfer[1].len = 6;

status = ioctl(fd, SPI_IOC_MESSAGE(2), xfer);

if (status < 0) {

perror("SPI_IOC_MESSAGE");

return;

}

printf("response(%d): ", status);

for (bp = buf; len; len--)

printf("%02x ", *bp++);

printf("\n");

}

Here is how the application runs on the STM32F4 target:

~ # /spidev_flash /dev/spidev3.0

response(7): 20 20 16 10 00 00 ~ #

SPI输出数据的同时必将读回数据来，因为要读回6个数据来，所以这里使用了缓冲区1的长度为6.

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