#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

char currentVolume;
int digiPot;

void setLVolume(char Volume) {
  int result;

  // Send the lower 5 bits (0-32) of Volume to the volume register for channel 0
  result = wiringPiI2CWrite(digiPot, Volume & 0x1F);

  if(result == -1) {
    printf("Error writing to digital potentiometer\n");
  }
}

void setRVolume(char Volume) {
  int result;

  // Send the lower 5 bits (0-32) of Volume to the volume register for channel 1
  result = wiringPiI2CWrite(digiPot, (Volume & 0x3F) | 0x40);

  if(result == -1) {
    printf("Error writing to digital potentiometer\n");
  }
}

void volumeUp(void) {
    setLVolume(++currentVolume);
    setRVolume(currentVolume);
}

void volumeDown(void) {
    setLVolume(--currentVolume);
    setRVolume(currentVolume);
}

int main (void) {
  // Start up WiringPi, using the GPIO pin numbering
  if (wiringPiSetupGpio() == -1)
    exit (1) ;

  // Setup I2C to talk to the digipot
  digiPot = wiringPiI2CSetup(0x50);
  if(digiPot == -1) {
    printf("Couldn't connect to digital poteniometer\n");
    return -1;
  }

  // Setup the PWM to generate the -5V rail for the digipot
  pinMode(18,PWM_OUTPUT);
  pwmSetMode(PWM_MODE_MS);
  pwmSetClock(512); // 512 = 17.5kHz, 256 = 35kHz, 128 = 70kHz, 64 = 140kHz
  pwmSetRange(2);
  pwmWrite (18, 1);

  // Enable the volume control
  pinMode(27,OUTPUT);
  digitalWrite(27,LOW);

  // Volume Up Button
  pinMode(22,INPUT);
  pullUpDnControl(22,PUD_UP);
  wirintPiISR(22, INT_EDGE_FALLING, &volumeUp);

  // Volume Down Button
  pinMode(23,INPUT);
  pullUpDnControl(23,PUD_UP);
  wirintPiISR(23, INT_EDGE_FALLING, &volumeDown);

  // Set the volume to about 30% on startup
  currentVolume = 10;
  setLVolume(currentVolume);
  setRVolume(currentVolume);

  // Any extra init code can go here

  for (;;) delay(1000);
}