/*
Code pour lire la data du I2C decibel meter
Pour compiler le code: gcc -o sound_meter sound_meter.c
Connexion I2C: 
SDA to Pi Pico GPIO 2
SCL to Pi Pico GPIO 3

Device connected on addr 0x48

to start the script:
sudo /var/www/nebuleair_pro_4g/sound_meter/sound_meter

0x00 : 	VERSION register
0x01 :  Device ID (byte 1)
0x02 : 	Device ID
0x03 : 	Device ID
0x04 : 	Device ID (byte 4)
0x05 : 	SKRATCH register
0x06 : 	CONTROL register
0x07 : 	TAVG high register
0x08 : 	TAVG low register
0x09 : 	RESET register

0x0A : Decibel register (Latest sound intensity value in decibels, averaged over the last Tavg time period.)

0x0B : Min register (Minimum value of decibel reading captured since power-up or manual reset of MIN/MAX registers.)
0x0C : Max register (Maximum value of decibel reading captured since power-up or manual reset of MIN/MAX registers.)

#Le Tavg est programmé sur 2 octets: le high byte et le low byte.
 0x07          #Averaging time (high byte) in milliseconds for calculating sound intensity levels. (default 0x03 -> 3)
 0x08          #Averaging time (low byte) in milliseconds for calculating sound intensity levels. (default 0xE8 -> 232)
 valeur = (Tavg_high x 256) + Tavg_low
		= (3 * 256) + 232
		= 1000 ms 
		= 1 s

*/

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>

int main()
{
	int file;
	char data;
 
	// Open I2C1 for reading the sound meter module registers
	if ((file = open("/dev/i2c-1", O_RDWR)) < 0)
	{
		perror("Failed to open I2C1!");
		exit(1);
	}
	
	// 0x48 is the decibel meter I2C address
	if (ioctl(file, I2C_SLAVE, 0x48) < 0)
	{
		perror("db Meter module is not connected/recognized at I2C addr = 0x48");
		close(file);
		exit(1);
	}
	
	// Decibel value is stored in register 0x0A
	data = 0x0A;

	// Write the register address (0x0A) to the device
	if (write(file, &data, 1) != 1)
	{
		perror("Failed to write register 0x0A");
		close(file);
		exit(1);
	}

	// Read one byte from the device
	if (read(file, &data, 1) != 1)
	{
		perror("Failed to read register 0x0A");
		close(file);
		exit(1);
	}

	// Display the sound level
	printf("%d\n", data);

	// Close the I2C connection
	close(file);
	return 0;
}