/*
 * MIT License
 * 
 * Copyright (c) 2018 Nis Wechselberg
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * Firmware for MiCS-6841-based I2C adapter board.
 * Implements a behaviour compatible to the Seeedstudio 
 * Grove Mutichannel Gas Sensor-library.
 * 
 * Using ATmega core from:
 * https://raw.githubusercontent.com/carlosefr/atmega/master/package_carlosefr_atmega_index.json
 * 
 * Pin mapping:
 * Heater Enable (out): PB0 / Digital 8 (Active low)
 * NH3 resistance (in): PC0 / Analog 0
 * RED resistance (in): PC1 / Analog 1
 * OX  resistance (in): PC2 / Analog 2
 * 
 * SDA: PC4 / Analog 4
 * SCL: PC5 / Analog 5
 */
#ifndef MiCS6814_V1_H
#define MiCS6814_V1_H


// Include Wire library for I2C support
#include <Wire.h>
#include <EEPROM.h>


// Pin mapping constants
#define HEATER      8
#define NH3_IN      A0
#define RED_IN      A1
#define OX_IN       A2


/*
 * I2C commands
 * 
 * Taken from Grove Mutichannel Gas Sensor Library, just some renaming done here
 */
#define CMD_GET_NH3             1     // Retrieve current resistance for NH3 sensor channel
#define CMD_GET_RED             2     // Retrieve current resistance for RED sensor channel
#define CMD_GET_OX              3     // Retrieve current resistance for OX sensor channel
#define CMD_GET_ALL             4     // Retrieve all sensor resistance channels
#define CMD_CHANGE_I2C          5     // Change I2C address of the sensor
#define CMD_READ_EEPROM         6     // Read stored uint16_t data from EEPROM (MSB is transmitted first)
#define CMD_SET_R0              7     // Set custom R0 values
#define CMD_GET_R0              8     // Retrieve current R0 values
#define CMD_GET_R0_DEFAULT      9     // Retrieve default R0 values
#define CMD_CONTROL_LED         10    // Control status LED (no LED on my board, but Grove supports is, so ... meh!)
#define CMD_CONTROL_PWR         11    // Heater control


/* EEPROM Addresses
 *  
 * These match the addresses used in the Grove library
 * If the library was implemented in a sensible fashion I would 
 * be free to use my own mapping here.
 * However, the library accesses eeprom data directly quite frequently, so ... meh!
 */
#define EEPROM_VERSION_ID       0     // Identifier for the current version, Grove uses value 1126 to identify version 2 of their sensor.
#define EEPROM_R0_DEFAULT_NH3   2
#define EEPROM_R0_DEFAULT_RED   4
#define EEPROM_R0_DEFAULT_OX    6
#define EEPROM_R0_NH3           8
#define EEPROM_R0_RED           10
#define EEPROM_R0_OX            12
#define EEPROM_I2C_ADDR         20

#define DATA_VERSION_ID         1126
#define DATA_I2C_ADDR           0x04
#define DATA_R0_DEFAULT_NH3     123
#define DATA_R0_DEFAULT_RED     123
#define DATA_R0_DEFAULT_OX      123


// Runtime data
uint32_t timer;             // Timer value of last update
uint16_t resistanceNH3;     // Current resistance value for NH3 channel
uint16_t resistanceRED;     // Current resistance value for RED channel
uint16_t resistanceOX;      // Current resistance value for OX channel
uint8_t  i2CResp[6];        // Buffer for I2C response
uint8_t  i2CRespLength;     // Amount of bytes to be sent to master

#endif