// Rapsberry Pi: SPI in C - Versione 0.51 - Luglio 2013
// Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/elettronica-di-base/RaspberryPi/spi-c.htm

// Compile:  gcc multi.c -std=c99 -o multi
// Run as user with R&W right on /dev/spidev0.* (NOT ROOT!)
// vv@vvrpi ~ $ ./multi 
// Using MAX1240 - Read multiple voltage

#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 SPI_SPEED 2000000                       // SPI frequency clock
#define VREF 2.500				// MAX1240 voltag reference
#define SAMPLES 1000				// Number of samples

static const char *device = "/dev/spidev0.0";	// MAX1240 CD to RPi CS0
static uint8_t mode = SPI_MODE_0;		// SPI_MODE_0 

static void exit_on_error (const char *s)	// Exit and print error code
{ 	perror(s);
  	abort();
} 

int main(int argc, char *argv[])
{
	int fd;
	int data;
	double volt[SAMPLES];
	
      	uint16_t rx[SAMPLES];    	// RX buffer (16 bit unsigned integer array)
      	
        struct  spi_ioc_transfer tr[SAMPLES];

        for (int i = 0; i < SAMPLES; i++)
        {
          tr[i].tx_buf = (unsigned long)NULL;
          tr[i].rx_buf = (unsigned long)&rx[i];
          tr[i].len = 2;             
          tr[i].delay_usecs = 0;
          tr[i].speed_hz = SPI_SPEED;
          tr[i].bits_per_word = 8;
          tr[i].cs_change = 1;                                                                                        
        }
                
       	// Open SPI device
       	if ((fd = open(device, O_RDWR)) < 0) exit_on_error ("Can't open SPI device");

	// Set SPI mode
	if (ioctl(fd, SPI_IOC_WR_MODE, &mode) == -1) exit_on_error ("Can't set SPI mode");

       	// Read data
       	if (ioctl(fd, SPI_IOC_MESSAGE(SAMPLES), tr) < 1) exit_on_error ("Can't send SPI message");
                
        for (int i = 0; i < SAMPLES; i++)	// Convert to voltage
        { printf("RAW; %X  ", rx[i]);
          if (!(rx[i] & 0x0080) ) printf (" FAIL  ");		// FAIL FAIL FAIL! (see text)
          data = ((rx[i] << 5) | (rx[i] >> 11)) & 0x0FFF;
          printf ("Data %d \n", data);
          volt[i] = VREF * data / 4096;
        }
        
       	printf("Rapsberry Pi: SPI in C - Versione 0.5 - Luglio 2013\n");
       	printf("Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)\n");
        printf("Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.\n");
        printf("Creative Commons | Attribution-Share Alike 3.0 Unported\n");
        printf("https://www.vincenzov.net/tutorial/elettronica-di-base/RaspberryPi/spi-c.htm\n\n");

        printf("Reading multiple data from MAX1240 on %s\n\n", device);
        
        for (int i = 0; i < SAMPLES; i++)
          printf("Voltage: %f V \n", volt[i]);
                          
	close(fd);

	return (0);
}