spi.c

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>


static void pabort(const char *s)
{
		perror(s);
		abort();
}
int main()
{
	int dev = open("/dev/spidev0.0", O_RDWR); //open file descriptor to the spi device
	int file = open("spictest.bin", O_RDWR| O_TRUNC | O_CREAT , S_IRWXU); // open a file in the current folder, delete previous content, create a new file if it doenst exist, set permissions
	
	if (dev < 0)
		pabort("can't open device");
	int ret;
	int mode = SPI_MODE_1;	
	ret = ioctl(dev, SPI_IOC_WR_MODE, &mode); // set and get spi parameters
	if (ret == -1)	
		pabort("can't set spi mode");
	ret = ioctl(dev, SPI_IOC_RD_MODE, &mode);
	if (ret == -1)
		pabort("can't get spi1 mode");
	int bits = 8;
	ret = ioctl(dev, SPI_IOC_WR_BITS_PER_WORD ,&bits );
	if (ret == -1)
		pabort("can't set bits per word");
	ret = ioctl(dev, SPI_IOC_RD_BITS_PER_WORD, &bits);
	if (ret == -1)
		pabort("can't get bits per word");
	int speed = 80000000;
	ret = ioctl(dev, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
	if(ret == -1)
		pabort("can't set max speed");
	ret = ioctl(dev, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
	if(ret == -1)
		pabort("can't get max speed");

	int sector = 1024; // set how much bytes to read in one transfer
	u_int8_t tx[4+1024]; // create array with 4 bytes for the command + address and [sector] bytes for reading
        u_int8_t rx[4+1024] = {0, };
	
	u_int8_t cmd = 0x03; // what command to execute (Read data)
	int address;	
	
        struct spi_ioc_transfer tr = { // fill the struct with the arrays, length of the transfer, delay, speed and bits per word
               	.tx_buf = (unsigned long)tx,
               	.rx_buf = (unsigned long)rx,
               	.len = 4+sector,
               	.delay_usecs = 0,
               	.speed_hz = speed,
               	.bits_per_word = bits,
       	};

	int transfers=1024*(4096/sector); // calculate how many transfers to do
	
	for(int i=0;i<transfers;i++){
		address = i*sector; // which address to start reading from	
		tx[0] = cmd; // set first byte as the command
		tx[1] = (address >> 16) & 0b11111111; // split address to the next 3 bytes
		tx[2] = (address >> 8) & 0b11111111;
		tx[3] = address & 0b11111111;
		
        	ret = ioctl(dev, SPI_IOC_MESSAGE(1), &tr); // run the transfer using the struct
        	if (ret < 1)
                	pabort("can't send spi message");

		lseek(file,0,SEEK_END); // move the file pointer to the end of the output file
		write(file,&(rx[4]),sector); // write from the 5th byte of the rx array, the first for are from the writing of the command
	}
	close(dev);// close both files
	close(file);
}