// need 0.1uf cap between vcc and ground for proper operation
// need 10k pull up resistor on scl and sda for i2c to work correctly

// Pin Mappings (Per TinyCore)
// ATTiny Pin  -- Arduino Pin
//    01           17/PA2/RESET
//    02           0/PD0/RXD
//    03           1/PD1/TXD
//    04           2/PA1/XTAL2
//    05           3/PA0/XTAL1
//    06           4/PD2/INT0
//    07           5/PD3/INT1
//    08           6/PD4
//    09           7/PD5
//    10           GND 
//    11           8/PD6
//    12           9/PB0/PCINT0
//    13           10/PB1/PCINT1
//    14           11/PB2/PCINT2/OC0A
//    15           12/PB3/PCINT3/OC1A
//    16           13/PB4/PCINT4/OC1B
//    17           14/PB5/PCINT5/MOSI/DI/SDA
//    18           15/PB6/PCINT6/MISO/DO
//    19           16/PB7/PCINT7/SCK/SCL
//    20           VCC

// i2c ATTiny Pins
// sda: 17
// scl: 19

// DIP Switch ATTiny Pins
// 2 - 9

#define I2C_ADDRESS 0x96

#include <Wire.h>

void setup() {
  pinMode(0, INPUT);
  pinMode(1, INPUT);
  pinMode(2, INPUT);
  pinMode(3, INPUT);
  pinMode(4, INPUT);
  pinMode(5, INPUT);
  pinMode(6, INPUT);
  pinMode(7, INPUT);
  
  Wire.begin(I2C_ADDRESS);
  Wire.onRequest(requestEvent);
}

void loop() {
  delay(100);
}

// function that executes whenever data is requested by master
// this function is registered as an event, see setup()
byte dip_switch = 0b00000000;
void requestEvent() {
  bitWrite(dip_switch, 0, digitalRead(0));
  bitWrite(dip_switch, 1, digitalRead(1));
  bitWrite(dip_switch, 2, digitalRead(2));
  bitWrite(dip_switch, 3, digitalRead(3));
  bitWrite(dip_switch, 4, digitalRead(4));
  bitWrite(dip_switch, 5, digitalRead(5));
  bitWrite(dip_switch, 6, digitalRead(6));
  bitWrite(dip_switch, 7, digitalRead(7));
  Wire.write(dip_switch);
}