// File: lm75aWW.cpp
// lm75aww.cpp
// Talk to lm75a - WRONG WAY - example of Wrong Way to do it
// Author: Jim Merkle, 10/31/2017

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#include <stdint.h>
#include <errno.h>
#include <linux/i2c.h>
#include <time.h>            // nanosleep

#define PROG_NAME	"lm75aww"

// I2C Address
#define LM75A   0x48

#ifndef u8
typedef unsigned char u8;
#endif
#ifndef u16
typedef unsigned short u16;
#endif

// LM75A Registers
#define LM75A_REG_TEMP    0
#define LM75A_REG_CONF    1
#define LM75A_REG_THYST   2
#define LM75A_REG_TOS     3
#define LM75A_REG_PROD_ID 7  /* only applicable for TI manufactured part */

// Power On Defaults:
// 0: Read only temperature - 2 bytes
// 1: 0x00 Configuration
// 2: 0x4B THYST - 75 degrees C - 2 bytes
// 3: 0x50 TOS - 80 degrees C - 2 bytes
// 7: 0xA1 (TI only)

void msleep(int milliseconds)
{
	//usleep(milliseconds * 1000); // limited method
	struct timespec ts;
	ts.tv_sec = milliseconds / 1000;
	ts.tv_nsec = (milliseconds % 1000) * 1000000;
	nanosleep(&ts, NULL);
}

void printbinary16(u16 number)
{
  u16 mask = 0x8000; // most significant bit set
  while (mask) {
	printf("%c",mask & number?'1':'0');
	mask >>= 1;
  }
}

void dump(void * address, int bytes)
{
    u8 * pData = (u8 *)address;
    int count = 0;
    // display rows of 16 bytes per row
    while (bytes > 0) {
        printf("%02X ",*pData++);
        count ++;
        if(!(count % 16)) printf("\n");
        bytes--;
    }
}

int main(int argc, char * argv[])
{
	//printf("Content-type: text/html\n\n");
	// Open the i2c bus device where the chip resides
	int file = open("/dev/i2c-1",O_RDWR);
	if(file<0) {
		printf("Failed to open the bus.");
		/* ERROR HANDLING; you can check errno to see what went wrong */
		exit(1);
	}

	// Method to define the default I2C device to interract with - NOT NEEDED for correct method
	int addr = LM75A;          // The I2C address of the I2C device
	if (ioctl(file, I2C_SLAVE, addr) < 0) {
		printf("Failed to acquire bus access and/or talk to slave.\n");
		/* ERROR HANDLING; you can check errno to see what went wrong */
		exit(1);
	}

	// By default, the LM75A configuration register is 0x00, and index points to register 0x00 (Temperature)
	
	while (1) {
		//u8 index = LM75A_REG_TEMP; // Read temperature register
		//ssize_t write(int fd, const void *buf, size_t count);
		//ssize_t read(int fd, void *buf, size_t count);
		u8 temperatureRegs[2]; // The MSB (first byte) is degree C units, the LSB is fractional component


		// Wrong way to read
		ssize_t bytesRead = read(file,temperatureRegs,2);
		if(bytesRead != 2) {
		  printf("read() error! bytesRead: %d\n",bytesRead);
		  sleep(2);
		  continue;
		}
		//printf("bytesRead: %d\n",bytesRead);
		//dump(temperatureRegs,sizeof(temperatureRegs));

        // This should be accurate for both positive and negative temperatures:
        u16 uTemp = (u16)temperatureRegs[0] << 8 | (u16)temperatureRegs[1]; // high byte followed by low byte
		
		float fTemp = (short)uTemp;
		fTemp /= 256; // The float will keep the remainder
		// Convert into Fahrenheit
		float fTempf = fTemp*9/5 + 32;
		//printf("\033cTemp %0.1fF\n",fTempf);
		//printbinary16(uTemp);
		printf("  0x%04X  %0.3fC  ",uTemp,fTemp);
		printf("%0.1fF\n",fTempf);

		sleep(1);
	}

	// clean up
	close(file);


	return 0;
}