Tooltron

#include "cardreader.h"

//#define SD

#define CR_CL       (_BV(PIND5))

#define CR_CLK      (_BV(PIND6))

#define CR_DATA     (_BV(PIND7))

#ifdef TRACK2

    #define CR_MAX_IDX  4

    #define CR_SS       ':'         // Start sentinal

#else

    #define CR_MAX_IDX  6

    #define CR_SS       '%'         // Start sentinal

#endif

#define CR_ES       '?'         // End sentinal

// This is only written in the PCINT2 intterupt or in the main loop

// but not concurrently. read_card acts as an implicit lock

volatile cr_flag_t cr_flag;

volatile uint8_t cr_buf[512];

volatile uint16_t cr_buf_idx;

volatile uint8_t read_card;

#ifdef TRACK2

const char cr_dict[] = {'0', '1', '2', '3', '4', '5', '6', '7',

                        '8', '9', ':', ';', '<', '=', '>', '?'};

#else

const char cr_dict[] = {' ', '!', '"', '#', '$', '%', '&', '\'',

                        '(', ')', '*', '+', ',', '-', '.', '/',

                        '0', '1', '2', '3', '4', '5', '6', '7',

                        '8', '9', ':', ';', '<', '=', '>', '?',

                        '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',

                        'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',

                        'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',

                        'X', 'Y', 'Z', '[', '\\',']', '^', '_'};

#endif

void card_reader_setup(void) {

    // Turn on pin interrupts for pins D7, D6, D5

    PCICR = _BV(PCIE2);

    PCMSK2 = _BV(PCINT22) | _BV(PCINT21);

    // Make pins D7, D6, D5 inputs

    DDRD &= ~_BV(DDD7) & ~_BV(DDD6) & ~_BV(DDD5); 

    cr_buf_idx = 0;

    cr_flag = CR_NONE;

    read_card = 0;

}

int8_t parse_card(uint8_t *buf, uint8_t *buflen) {

    int32_t i = cr_buf_idx - 1;

    uint8_t j = 0;

    uint8_t start_sentinal = 0;

    uint8_t byte_idx = 0;

    uint8_t byte = 0;

    uint8_t parity;

    // Look for the start sentinal

    while (start_sentinal == 0) {

        byte = (((byte >> 1) & 0x1F) | (cr_buf[i] << 5));

        if (cr_dict[byte] == CR_SS) {

            start_sentinal = 1;

            (buf)[j++] = cr_dict[byte];

            // Skip parity bit

            i--;

        }

        // Increment bits

        i--;

        // Ran out of buffer to search, no start sentinal found

        if (i == 0) {

            return CR_ERR_NO_START;

        }

    }

    // Prepare for reading of data

    byte = 0;

    byte_idx = 0;

    parity = 0;

    while (i >= 0) {

        // Parity bit

        if (byte_idx == CR_MAX_IDX) {

            if (!(cr_buf[i]) != (parity % 2)) {

                return CR_ERR_BAD_PARITY;

            }

            (buf)[j++] = cr_dict[byte];

            // Stop at the stop sentinal

            if (cr_dict[byte] == CR_ES) {

                *buflen = j;

                return 0;

            }

            byte_idx = 0;

            byte = 0;

            parity = 0;

        // Data bits

        } else {

            byte = (((byte >> 1) & 0x1F) | (cr_buf[i] << 5));

            byte_idx++;

            parity += cr_buf[i];

        }

        // Goto next bit in cr_buf

        i--;

    }

    return CR_ERR_NO_STOP;

}

ISR(PCINT2_vect) {    

    static uint8_t reading = 0;         // Currently reading

    // Only read card if we are expecting it

    if (!read_card) {

        return;

    }

    // Check if the card is inserted or not

    if (!(PIND & CR_CL) && (!reading)) {

        cr_flag = CR_NONE;

        cr_buf_idx = 0;

        reading = 1;

    // check if the card has finished swiping

    } else if (PIND & CR_CL) {

        cr_flag = CR_GOOD;

        reading = 0;

        return;

    }

    // Read data in on the downtick of the clock

    if (!(PIND & CR_CLK)) {

        // Read data from card reader and flip since ours inverts

        cr_buf[cr_buf_idx] = !(PIND & CR_DATA);

        cr_buf_idx++;

    }

}