/*
 * This program reads/writes the EEPROM on the Digilent Orbit BoosterPack
 * The Orbit BoosterPack has a Microchip 24LC256 I2C EEPROM.
 */

#include "TM4C123GH6PM.h"

void I2C0_init(void);
int I2C0_byteRead(int slaveAddr, short memAddr, unsigned char* data);
int I2C0_byteWrite(int slaveAddr, short memAddr, const unsigned char data);

#define SLAVE_ADDR 0x54     /* 1010 100. Microchip 24LC256 */

int main(void) {
    volatile int error;

    unsigned char buffer[8];
    short addr;

    I2C0_init();
    
    addr = 0x34;
    error = I2C0_byteWrite(SLAVE_ADDR, addr, 'M');
    error = I2C0_byteRead(SLAVE_ADDR, addr, buffer);
    
    while(1) {
    }
}

// Wait until I2C master is not busy and return error code.
// Busy status bit has a latency.  The function call overhead takes care of it.
static int I2C_wait_till_done(void) {
    // wait until I2C master is not busy
    while(I2C0->MCS & 1);
    // return I2C error code
    return I2C0->MCS & 0xE;
}

void I2C0_init(void) {
    SYSCTL->RCGCGPIO |= 0x02;   // enable clock to GPIOB
    SYSCTL->RCGCI2C |= 0x01;    // enable clock to I2C0

    // PORTB 2, 3 for I2C0
    GPIOB->AFSEL |= 0x0C;       // PORTB 2, 3 for I2C0
    GPIOB->PCTL &= ~0x0000FF00; // PORTB 2, 3 for I2C0
    GPIOB->PCTL |= 0x00003300;
    GPIOB->DEN |= 0x0C;         // PORTB 2, 3 as digital pins
    GPIOB->ODR |= 0x08;         // PORTB 2, 3 as open drain

    I2C0->MCR = 0x10;   // master mode
    I2C0->MTPR = 6;     // 100 kHz @ 16 MHz
    //I2C0->MTPR = 24;     // 50 kHz @ 50 MHz
}

// Write one byte with two byte memory address write first
int I2C0_byteWrite(int slaveAddr, short memAddr, const unsigned char data) {
    int error;

    // write: S-(addr+w)-ACK-addrH-ACK-addrL-ACK-data-ACK-P
    I2C0->MSA = slaveAddr << 1;
    I2C0->MDR = (memAddr >> 8) & 0xFF;  // send high byte of memory address
    I2C0->MCS = 3;                      // S-(addr+w)-ACK-addrH-ACK

    error = I2C_wait_till_done();   // wait until write is complete
    if (error)
        return error;

    I2C0->MDR = memAddr & 0xFF;     // send low byte of memory address
    I2C0->MCS = 1;                  // -addrL-ACK-

    error = I2C_wait_till_done();   // wait until write is complete
    if (error)
        return error;

    I2C0->MDR = data;               // write the data
    I2C0->MCS = 5;                  // -data-ACK-P
    error = I2C_wait_till_done();   // wait until write is complete
    while(I2C0->MCS & 0x40);        // wait until bus is not busy
    error = I2C0->MCS & 0xE;
    if (error)
        return error;

    // polling for programming complete (wait until an ack for address write)
    do
    {
        I2C0->MSA = slaveAddr << 1;
        I2C0->MDR = memAddr;
        I2C0->MCS = 7;                      // S-(addr+w)-ACK-addr-ACK=P
        error = I2C_wait_till_done();       // wait until write is complete
        while(I2C0->MCS & 0x40);            // wait until bus is not busy
    } while(I2C0->MCS & 4);                 // repeat if address was not acked
    return 0;
}

// Read one byte with two byte memory address write first
int I2C0_byteRead(int slaveAddr, short memAddr, unsigned char* data) {
    int error;

    // read: S-(addr+w)-ACK-addrH-ACK-addrL-ACK-S-(addr+r)-ACK-data-NACK-P
    I2C0->MSA = slaveAddr << 1;
    I2C0->MDR = (memAddr >> 8) & 0xFF;
    I2C0->MCS = 3;                      // S-(addr+w)-ACK-addrH-ACK
    error = I2C_wait_till_done();
    if (error)
        return error;

    I2C0->MDR = memAddr & 0xFF;         // send low byte of memory address
    I2C0->MCS = 0x1;                    // -addrL-ACK-
    error = I2C_wait_till_done();
    if (error)
        return error;

    I2C0->MSA = (slaveAddr << 1) + 1;   // restart and read
    I2C0->MCS = 0x7;                    // -S-(addr+r)-data-NACK-P
    error = I2C_wait_till_done();

    *data = I2C0->MDR;                  // get the data read
    while(I2C0->MCS & 0x40);            // wait until bus is not busy

    return 0;
}

// This function is called by the startup assembly
// code to perform system specific initialization tasks.
void SystemInit(void) {
    // Grant coprocessor access
    // This is required since TM4C123G has
    // a floating point coprocessor
    SCB->CPACR |= 0x00f00000;
}