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#include "defines.h"
#include "I2C1.h"

extern I2C1_DATA i2c_data;

// Set up the data structures for the base_I2C.code
// Should be called once before any i2c routines are called
void I2C1_Init(void) {
    I2C_1_CLK_TRIS = 1;
    I2C_1_DAT_TRIS = 1;
    
    i2c_data.buffer_in_len = 0;
    i2c_data.buffer_in_read_ind = 0;
    i2c_data.buffer_in_write_ind = 0;
    
    i2c_data.operating_state = I2C_IDLE;
    i2c_data.return_status = 0;

    i2c_data.master_dest_addr = 0;
    i2c_data.master_status = I2C_MASTER_IDLE;
    
    // Enable I2C interrupt
    PIE1bits.SSP1IE = 1;
}

// Setup the PIC to operate as a master.
void I2C1_Configure_Master(uint8_t speed) {
    SSP1STAT = 0x0;
    SSP1CON1 = 0x0;
    SSP1CON2 = 0x0;
    SSP1CON3 = 0x0;
    SSP1CON1bits.SSPM = 0x8; // I2C Master Mode
    if (speed == 0x01) {
        SSP1ADD = 0x13;         // Operate at 400KHz (32MHz)
        SSP1STATbits.SMP = 1;    // Disable Slew Rate Control
    } else if (speed == 0x02) {
        SSP1ADD = 0x07;         // Operate at 1Mhz (32Mhz)
        SSP1STATbits.SMP = 1;    // Disable Slew Rate Control
    } else {
        SSP1ADD = 0x4F;         // Operate at 100KHz (32MHz)
        SSP1STATbits.SMP = 0;    // Enable Slew Rate Control
    }
    SSP1CON1bits.SSPEN = 1;  // Enable MSSP1 Module
}

// Sends length number of bytes in msg to specified address (no R/W bit)
void I2C1_Master_Send(uint8_t address, uint8_t length, uint8_t *msg) {
    if (length == 0)
        return;
    
    // Copy message to send into buffer and save length/address
    for (uint8_t i = 0; i < length; i++) {
        i2c_data.buffer_in[i] = msg[i];
    }
    i2c_data.buffer_in_len = length;
    i2c_data.master_dest_addr = address;
    i2c_data.buffer_in_read_ind = 0;
    i2c_data.buffer_in_write_ind = 0;

    // Change status to 'next' operation
    i2c_data.operating_state = I2C_SEND_ADDR;
    i2c_data.master_status = I2C_MASTER_SEND;
    
    // Generate start condition
    SSP1CON2bits.SEN = 1;
}

// Reads length number of bytes from address (no R/W bit)
void I2C1_Master_Recv(uint8_t address, uint8_t length) {
    if (length == 0)
        return;

    // Save length and address to get data from
    i2c_data.buffer_in_len = length;
    i2c_data.master_dest_addr = address;
    i2c_data.buffer_in_read_ind = 0;
    i2c_data.buffer_in_write_ind = 0;

    // Change status to 'next' operation
    i2c_data.operating_state = I2C_SEND_ADDR;
    i2c_data.master_status = I2C_MASTER_RECV;
    
    // Generate start condition
    SSP1CON2bits.SEN = 1;
}

// Writes msg to address then reads length number of bytes from address
void I2C1_Master_Restart(uint8_t address, uint8_t msg, uint8_t length) {
    uint8_t c;
    if (length == 0) {
        c = msg;
        I2C1_Master_Send(address, 1, &c);
        return;
    }

    // Save length and address to get data from
    i2c_data.buffer_in[0] = msg;
    i2c_data.buffer_in_len = length;
    i2c_data.master_dest_addr = address;
    i2c_data.buffer_in_read_ind = 0;
    i2c_data.buffer_in_write_ind = 0;

    // Change status to 'next' operation
    i2c_data.operating_state = I2C_SEND_ADDR;
    i2c_data.master_status = I2C_MASTER_RESTART;

    // Generate start condition
    SSP1CON2bits.SEN = 1;
}

void I2C1_Interrupt_Handler() {
    // If we are in the middle of sending data
    if (i2c_data.master_status == I2C_MASTER_SEND) {
        switch (i2c_data.operating_state) {
            case I2C_IDLE:
                break;
            case I2C_SEND_ADDR:
                // Send the address with read bit set
                i2c_data.operating_state = I2C_CHECK_ACK_SEND;
                SSP1BUF = (i2c_data.master_dest_addr << 1) | 0x0;
                break;
            case I2C_CHECK_ACK_SEND:
                // Check if ACK is received or not
                if (!SSP1CON2bits.ACKSTAT) {
                    // If an ACK is received, send next byte of data
                    if (i2c_data.buffer_in_read_ind < i2c_data.buffer_in_len) {
                        SSP1BUF = i2c_data.buffer_in[i2c_data.buffer_in_read_ind];
                        i2c_data.buffer_in_read_ind++;
                    } else {
                        // If no more data is to be sent, send stop bit
                        i2c_data.operating_state = I2C_IDLE;
                        SSP1CON2bits.PEN = 1;
                        i2c_data.master_status = I2C_MASTER_IDLE;
                        i2c_data.return_status = I2C_SEND_OK;
                    }
                } else {
                    // If a NACK is received, stop transmission and send error
                    i2c_data.operating_state = I2C_IDLE;
                    SSP1CON2bits.PEN = 1;
                    i2c_data.master_status = I2C_MASTER_IDLE;
                    i2c_data.return_status = I2C_SEND_FAIL;
                }
                break;
        }
    // If we are in the middle of receiving data
    } else if (i2c_data.master_status == I2C_MASTER_RECV) {
        switch (i2c_data.operating_state) {
            case I2C_IDLE:
                break;
            case I2C_SEND_ADDR:
                // Send address with write bit set
                i2c_data.operating_state = I2C_CHECK_ACK_RECV;
                uint8_t tmp = (i2c_data.master_dest_addr << 1);
                tmp |= 0x01;
                SSP1BUF = tmp;
                break;
            case I2C_CHECK_ACK_RECV:
                // Check if ACK is received
                if (!SSP1CON2bits.ACKSTAT) {
                    // If an ACK is received, set module to receive 1 byte of data
                    i2c_data.operating_state = I2C_RCV_DATA;
                    SSP1CON2bits.RCEN = 1;
                } else {
                    // If a NACK is received, stop transmission and send error
                    i2c_data.operating_state = I2C_IDLE;
                    SSP1CON2bits.PEN = 1;
                    i2c_data.master_status = I2C_MASTER_IDLE;
                    i2c_data.return_status = I2C_RECV_FAIL;
                }
                break;
            case I2C_RCV_DATA:
                // On receive, save byte into buffer
                // TODO: Handle I2C buffer overflow
                i2c_data.buffer_in[i2c_data.buffer_in_write_ind] = SSP1BUF;
                i2c_data.buffer_in_write_ind++;
                if (i2c_data.buffer_in_write_ind < i2c_data.buffer_in_len) {
                    // If we still need to read, send an ACK to the slave
                    i2c_data.operating_state = I2C_REQ_DATA;
                    SSP1CON2bits.ACKDT = 0;  // ACK
                    SSP1CON2bits.ACKEN = 1;
                } else {
                    // If we are done reading, send an NACK to the slave
                    i2c_data.operating_state = I2C_SEND_STOP;
                    SSP1CON2bits.ACKDT = 1;  // NACK
                    SSP1CON2bits.ACKEN = 1;
                }
                break;
            case I2C_REQ_DATA:
                // Set module to receive one byte of data
                i2c_data.operating_state = I2C_RCV_DATA;
                SSP1CON2bits.RCEN = 1;
                break;
            case I2C_SEND_STOP:
                // Send the stop bit and copy message to send to Main()
                i2c_data.operating_state = I2C_IDLE;
                SSP1CON2bits.PEN = 1;
                i2c_data.master_status = I2C_MASTER_IDLE;
                i2c_data.return_status = I2C_RECV_OK;
                break;
        }
    } else if (i2c_data.master_status == I2C_MASTER_RESTART) {
        switch (i2c_data.operating_state) {
            case I2C_IDLE:
                break;
            case I2C_SEND_ADDR:
                // Send the address with read bit set
                i2c_data.operating_state = I2C_CHECK_ACK_SEND;
                SSP1BUF = (i2c_data.master_dest_addr << 1) | 0x0;
                break;
            case I2C_CHECK_ACK_SEND:
                // Check if ACK is received or not
                if (!SSP1CON2bits.ACKSTAT) {
                    // If an ACK is received, send first byte of data
                    SSP1BUF = i2c_data.buffer_in[0];
                    i2c_data.operating_state = I2C_CHECK_ACK_RESTART;
                } else {
                    // If a NACK is received, stop transmission and send error
                    i2c_data.operating_state = I2C_IDLE;
                    SSP1CON2bits.PEN = 1;
                    i2c_data.master_status = I2C_MASTER_IDLE;
                    i2c_data.return_status = I2C_SEND_FAIL;
                }
                break;
            case I2C_CHECK_ACK_RESTART:
                if (!SSP1CON2bits.ACKSTAT) {
                    SSP1CON2bits.RSEN = 1;
                    i2c_data.operating_state = I2C_SEND_ADDR_2;
                } else {
                    // If a NACK is received, stop transmission and send error
                    i2c_data.operating_state = I2C_IDLE;
                    SSP1CON2bits.PEN = 1;
                    i2c_data.master_status = I2C_MASTER_IDLE;
                    i2c_data.return_status = I2C_SEND_FAIL;
                }
                break;
            case I2C_SEND_ADDR_2:
                // Send the address with read bit set
                i2c_data.operating_state = I2C_CHECK_ACK_RECV;
                uint8_t tmp = (i2c_data.master_dest_addr << 1);
                tmp |= 0x01;
                SSP1BUF = tmp;
                break;
            case I2C_CHECK_ACK_RECV:
                // Check if ACK is received
                if (!SSP1CON2bits.ACKSTAT) {
                    // If an ACK is received, set module to receive 1 byte of data
                    i2c_data.operating_state = I2C_RCV_DATA;
                    SSP1CON2bits.RCEN = 1;
                } else {
                    // If a NACK is received, stop transmission and send error
                    i2c_data.operating_state = I2C_IDLE;
                    SSP1CON2bits.PEN = 1;
                    i2c_data.master_status = I2C_MASTER_IDLE;
                    i2c_data.return_status = I2C_RECV_FAIL;
                }
                break;
            case I2C_RCV_DATA:
                // On receive, save byte into buffer
                // TODO: Handle I2C buffer overflow
                i2c_data.buffer_in[i2c_data.buffer_in_write_ind] = SSP1BUF;
                i2c_data.buffer_in_write_ind++;
                if (i2c_data.buffer_in_write_ind < i2c_data.buffer_in_len) {
                    // If we still need to read, send an ACK to the slave
                    i2c_data.operating_state = I2C_REQ_DATA;
                    SSP1CON2bits.ACKDT = 0;  // ACK
                    SSP1CON2bits.ACKEN = 1;
                } else {
                    // If we are done reading, send an NACK to the slave
                    i2c_data.operating_state = I2C_SEND_STOP;
                    SSP1CON2bits.ACKDT = 1;  // NACK
                    SSP1CON2bits.ACKEN = 1;
                }
                break;
            case I2C_REQ_DATA:
                // Set module to receive one byte of data
                i2c_data.operating_state = I2C_RCV_DATA;
                SSP1CON2bits.RCEN = 1;
                break;
            case I2C_SEND_STOP:
                // Send the stop bit
                i2c_data.operating_state = I2C_IDLE;
                SSP1CON2bits.PEN = 1;
                i2c_data.master_status = I2C_MASTER_IDLE;
                i2c_data.return_status = I2C_RECV_OK;
                break;
        }
    }
}

/* Returns 0 if I2C module is currently busy, otherwise returns status code */
uint8_t I2C1_Get_Status() {
//    if (i2c_data.operating_mode == I2C_MODE_MASTER) {
        if (i2c_data.master_status != I2C_MASTER_IDLE || i2c_data.buffer_in_len == 0) {
            return 0;
        } else {
            return i2c_data.return_status;
        }
}

uint8_t I2C1_Buffer_Len() {
    return i2c_data.buffer_in_len;
}

/* Returns 0 if I2C module is currently busy, otherwise returns buffer length */
uint8_t I2C1_Read_Buffer(uint8_t *buffer) {
    uint8_t i = 0;
    while (i2c_data.buffer_in_len != 0) {
        buffer[i] = i2c_data.buffer_in[i2c_data.buffer_in_read_ind];
        i++;
        if (i2c_data.buffer_in_read_ind == MAXI2C1BUF-1) {
            i2c_data.buffer_in_read_ind = 0;
        } else {
            i2c_data.buffer_in_read_ind++;
        }
        i2c_data.buffer_in_len--;
    }
    return i;
}