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- #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;
- }
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