#include <stdio.h>

#include <stdio.h>
#include "sdc.h"

// Add data to crc with polynomial 0x1021
// https://stackoverflow.com/a/23726131
static uint16_t crc16(uint16_t crc, uint8_t data)
{
uint8_t x = crc >> 8 ^ data;
x ^= x>>4;
crc = (crc << 8) ^ ((uint16_t)(x << 12)) ^ ((uint16_t)(x <<5)) ^ ((uint16_t)x);
return crc;
}

void sdc_init(SDC *sdc)
{
sdc->initstat = 0;
sdc->recvidx = 0;
sdc->sendidx = -1;
sdc->fp = NULL;
sdc->cmd17bytes = -1;
sdc->cmd24bytes = -2;
}

byte sdc_spix(SDC *sdc, byte val)
{
byte resp = 0xff;
if (sdc->initstat < 8) {
// not woken yet.
sdc->initstat++;
return resp;
}
if (sdc->sendidx >= 0) {
resp = sdc->sendbuf[sdc->sendidx++];
if (sdc->sendidx == 5) {
sdc->sendidx = -1;
}
return resp;
}
if (sdc->cmd17bytes >= 0) {
if (sdc->fp) {
resp = getc(sdc->fp);
}
sdc->crc16 = crc16(sdc->crc16, resp);
sdc->cmd17bytes++;
if (sdc->cmd17bytes == 512) {
sdc->sendbuf[3] = sdc->crc16 >> 8;
sdc->sendbuf[4] = sdc->crc16 & 0xff;
sdc->sendidx = 3;
sdc->cmd17bytes = -1;
}
return resp;
}
if (sdc->cmd24bytes == -1) {
if (val == 0xff) {
// it's ok to receive idle bytes before the data token.
return resp;
}
if (val == 0xfe) {
// data token, good
sdc->cmd24bytes = 0;
} else {
// something is wrong, cancel cmd24
sdc->cmd24bytes = -2;
}
return resp;
}
if (sdc->cmd24bytes >= 0) {
if (sdc->cmd24bytes < 512) {
if (sdc->fp) {
putc(val, sdc->fp);
}
sdc->crc16 = crc16(sdc->crc16, val);
} else if (sdc->cmd24bytes == 512) {
// CRC MSB
if (val == (sdc->crc16>>8)) {
fprintf(stderr, "Good CRC16 MSB\n");
} else {
fprintf(stderr, "Bad CRC16 MSB\n");
}
} else {
if (val == (sdc->crc16&0xff)) {
fprintf(stderr, "Good CRC16 LSB\n");
} else {
fprintf(stderr, "Bad CRC16 LSB\n");
}
// valid response for CMD24
sdc->sendbuf[4] = 0x05;
sdc->sendidx = 4;
sdc->cmd24bytes = -3;
}
sdc->cmd24bytes++;
return resp;
}
if ((sdc->recvidx == 0) && ((val > 0x7f) || (val < 0x40))) {
// not a command
return resp;
}
sdc->recvbuf[sdc->recvidx++] = val;
if (sdc->recvidx < 6) {
// incomplete command
return resp;
}
// Command complete
val &= 0x3f;
sdc->recvidx = 0;
uint8_t *b = sdc->recvbuf;
uint8_t cmd = b[0] & 0x3f;
uint16_t arg1 = (b[1] << 8) | b[2];
uint16_t arg2 = (b[3] << 8) | b[4];
// printf("cmd %02x %04x %04x\n", cmd, arg1, arg2);
if (sdc->initstat == 8) {
// At this stage, we're expecting CMD0
if (cmd == 0) {
sdc->initstat++;
sdc->sendbuf[4] = 0x01;
sdc->sendidx = 4;
}
return resp;
}
if (sdc->initstat == 9) {
// At this stage, we're expecting CMD8 with 0x1aa arg2
if ((cmd == 8) && (arg2 == 0x01aa)) {
sdc->initstat++;
sdc->sendbuf[0] = 0x01;
sdc->sendbuf[1] = 0;
sdc->sendbuf[2] = 0;
sdc->sendbuf[3] = 0x01;
sdc->sendbuf[4] = 0xaa;
sdc->sendidx = 0;
} else {
sdc-> initstat = 8;
}
return resp;
}
if (sdc->initstat == 10) {
// At this stage, we're expecting CMD55
if (cmd == 55) {
sdc->initstat++;
sdc->sendbuf[4] = 0x01;
sdc->sendidx = 4;
} else {
sdc->initstat = 8;
}
return resp;
}
if (sdc->initstat == 11) {
// At this stage, we're expecting CMD41
if ((cmd == 41) && (arg1 == 0x4000)) {
sdc->initstat++;
sdc->sendbuf[4] = 0x00;
sdc->sendidx = 4;
} else {
sdc->initstat = 8;
}
return resp;
}
// We have a fully initialized card.
if (cmd == 17) {
if (sdc->fp) {
fseek(sdc->fp, arg2*512, SEEK_SET);
}
sdc->sendbuf[3] = 0x00;
// data token
sdc->sendbuf[4] = 0xfe;
sdc->sendidx = 3;
sdc->cmd17bytes = 0;
sdc->crc16 = 0;
return resp;
}
if (cmd == 24) {
if (sdc->fp) {
fseek(sdc->fp, arg2*512, SEEK_SET);
}
sdc->sendbuf[4] = 0x00;
sdc->sendidx = 4;
sdc->cmd24bytes = -1;
sdc->crc16 = 0;
return resp;
}
// Simulate success for any unknown command.
sdc->sendbuf[4] = 0x00;
sdc->sendidx = 4;
return resp;
}