Added inital spi based sd card code. Working on CRC7 code that works.

fpga/zsbl/sd.c

@@ -0,0 +1,31 @@
+#include "sd.h"
+#include "spi.h"
+
+uint8_t crc7(uint8_t prev, uint8_t in) {
+    // CRC polynomial 0x89
+    uint8_t remainder = prev & in;
+    remainder ^= (remainder >> 4) ^ (remainder >> 7);
+    remainder ^= remainder << 4;
+    return remainder & 0x7f;
+}
+
+uint16_t crc16(uint16_t crc, uint8_t data) {
+    // CRC polynomial 0x11021
+    crc = (uint8_t)(crc >> 8) | (crc << 8);
+    crc ^= data;
+    crc ^= (uint8_t)(crc >> 4) & 0xf;
+    crc ^= crc << 12;
+    crc ^= (crc & 0xff) << 5;
+    return crc;
+}
+
+uint8_t sd_cmd(uint8_t cmd, uint32_t arg, uint8_t crc) {
+  spi_send_byte
+}
+
+void init_sd(){
+  init_spi();
+
+  
+}
+

fpga/zsbl/sd.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <stdint.h>
+
+uint8_t crc7(uint8_t prev, uint8_t in);
+uint16_t crc16(uint16_t crc, uint8_t data);
+uint8_t sd_cmd(uint8_t cmd, uint32_t arg, uint8_t crc);
+void init_sd();
+

fpga/zsbl/spi.c

@@ -48,4 +48,3 @@ uint8_t spi_send_byte(uint8_t byte) {
   return result;
 }
 
-

fpga/zsbl/spi.h

@@ -40,6 +40,7 @@
 void write_reg(uintptr_t addr, uint32_t value);
 uint32_t read_reg(uintptr_t addr);
 uint8_t spi_send_byte(uint8_t byte);
+
 void spi_init();
 
 #endif