// i2c-mcp4725-dac.cpp
//
// Written by Andrew Meyer <ajm@leaflabs.com>
// Modified by Marti Bolivar <mbolivar@leaflabs.com>
//
// Simple program showing how to control an MCP4725 DAC using the
// libmaple I2C interface. There's an MCP4725 breakout board available
// on SparkFun:
//
// http://www.sparkfun.com/products/8736
//
// How to use:
//
// 1. Connect the DAC SDA and SCL pins to I2C2, with a pullup
//    resistor (1 KOhm should work) to VCC.
// 2. Load the sketch and connect to SerialUSB.
// 3. Press the button.
//
// The program then makes sure the DAC is connected properly (during
// setup()), then has the DAC output a sawtooth wave (with loop()).

#include <wirish/wirish.h>
#include <libmaple/i2c.h>

#define MCP_ADDR         0x60
#define MCP_WRITE_DAC    0b01000000
#define MCP_WRITE_EEPROM 0b01100000
#define MCP_PD_NORMAL    0b00000000
#define MCP_PD_1K        0b00000010
#define MCP_PD_100K      0b00000100
#define MCP_PD_500K      0b00000110

static uint8 write_msg_data[3];
static i2c_msg write_msg;

static uint8 read_msg_data[5];
static i2c_msg read_msg;

/*
 * DAC control routines
 */

void mcp_i2c_setup(void) {
    write_msg.addr = MCP_ADDR;
    write_msg.flags = 0; // write, 7 bit address
    write_msg.length = sizeof(write_msg_data);
    write_msg.xferred = 0;
    write_msg.data = write_msg_data;

    read_msg.addr = MCP_ADDR;
    read_msg.flags = I2C_MSG_READ;
    read_msg.length = sizeof(read_msg_data);
    read_msg.xferred = 0;
    read_msg.data = read_msg_data;
}

void mcp_write_val(uint16 val) {
    write_msg_data[0] = MCP_WRITE_DAC | MCP_PD_NORMAL;
    uint16 tmp = val >> 4;
    write_msg_data[1] = tmp;
    tmp = (val << 4) & 0x00FF;
    write_msg_data[2] = tmp;

    i2c_master_xfer(I2C2, &write_msg, 1, 0);
}

uint16 mcp_read_val() {
    uint16 tmp = 0;

    i2c_master_xfer(I2C2, &read_msg, 1, 2);

    /* We don't care about the status and EEPROM bytes (0, 3, and 4). */
    tmp = (read_msg_data[1] << 4);
    tmp += (read_msg_data[2] >> 4);
    return tmp;
}

int mcp_test() {
    uint16 val;
    uint16 test_val = 0x0101;

    SerialUSB.println("Testing the MCP4725...");
    /* Read the value of the register (should be 0x0800 if factory fresh) */
    val = mcp_read_val();
    SerialUSB.print("DAC Register = 0x");
    SerialUSB.println(val, HEX);

    mcp_write_val(test_val);
    SerialUSB.print("Wrote 0x");
    SerialUSB.print(test_val, HEX);
    SerialUSB.println(" to the DAC");

    val = mcp_read_val();
    SerialUSB.print("DAC Register = 0x");
    SerialUSB.println(val, HEX);

    if (val != test_val) {
        SerialUSB.println("ERROR: MCP4725 not responding correctly");
        return 0;
    }

    SerialUSB.println("MCP4725 seems to be working");
    return 1;
}

/*
 * setup() and loop()
 */

void setup() {
    pinMode(BOARD_BUTTON_PIN, INPUT);
    i2c_master_enable(I2C2, 0);
    mcp_i2c_setup();

    waitForButtonPress();
    ASSERT(mcp_test());

    SerialUSB.println("Starting sawtooth wave");
}

void loop() {
    static uint16 dout = 0;

    mcp_write_val(dout);

    dout += 50;
    if (dout >= 32768) {
        dout = 0;
    }
}

// -- init() and main() -------------------------------------------------------

__attribute__((constructor)) void premain() {
    init();
}

int main(void) {
    setup();

    while (true) {
        loop();
    }
    return 0;
}