Diff: main.cpp

Revision:

0:9b6d6fa5c401

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Apr 17 23:34:09 2018 +0000
@@ -0,0 +1,232 @@
+#include "mbed.h"
+ /* SPI Command Format
+ * ------------------
+ * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
+ *
+ * +---------------+------------+------------+-----------+----------+--------------+
+ * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
+ * +---------------+------------+------------+-----------+----------+--------------+
+ *
+ * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
+ *
+ * All Application Specific commands shall be preceded with APP_CMD (CMD55).
+ *
+ * SPI Response Format
+ * -------------------
+ * The main response format (R1) is a status byte (normally zero). Key flags:
+ *  idle - 1 if the card is in an idle state/initialising
+ *  cmd  - 1 if an illegal command code was detected
+ *
+ *    +-------------------------------------------------+
+ * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
+ *    +-------------------------------------------------+
+ *
+ * R1b is the same, except it is followed by a busy signal (zeros) until
+ * the first non-zero byte when it is ready again.
+ *
+ * Data Response Token
+ * -------------------
+ * Every data block written to the card is acknowledged by a byte
+ * response token
+ *
+ * +----------------------+
+ * | xxx | 0 | status | 1 |
+ * +----------------------+
+ *              010 - OK!
+ *              101 - CRC Error
+ *              110 - Write Error
+ *
+ * Single Block Read and Write
+ * ---------------------------
+ *
+ * Block transfers have a byte header, followed by the data, followed
+ * by a 16-bit CRC. In our case, the data will always be 512 bytes.
+ *
+ * +------+---------+---------+- -  - -+---------+-----------+----------+
+ * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
+ * +------+---------+---------+- -  - -+---------+-----------+----------+
+ */
+
+
+#define SD_COMMAND_TIMEOUT 5000
+
+#define R1_IDLE_STATE           (1 << 0)
+#define R1_ERASE_RESET          (1 << 1)
+#define R1_ILLEGAL_COMMAND      (1 << 2)
+#define R1_COM_CRC_ERROR        (1 << 3)
+#define R1_ERASE_SEQUENCE_ERROR (1 << 4)
+#define R1_ADDRESS_ERROR        (1 << 5)
+#define R1_PARAMETER_ERROR      (1 << 6)
+
+#define SDCARD_FAIL 0
+#define SDCARD_V1   1
+#define SDCARD_V2   2
+#define SDCARD_V2HC 3
+#define SD_DBG             0
+
+SPI sd(PB_15, PB_14, PB_13); //miso,mosi, sclk
+DigitalOut ssel (PB_12);
+
+int cmd(int cmd, int arg);
+int cmd8();
+int cmd58();
+int initialise_card();
+int cdv;   
+  
+
+void main ()
+{
+    spi.format(16, 0);
+    sd.frequency(2);
+    while(1)
+     sd.write(0xAA);
+     
+    initialise_card();
+    
+}
+
+
+int cmd(int cmd, int arg) {
+    ssel = 0;
+
+    // send a command
+    sd.write(0x40 | cmd);
+    sd.write(arg >> 24);
+    sd.write(arg >> 16);
+    sd.write(arg >> 8);
+    sd.write(arg >> 0);
+    sd.write(0x95);
+
+    // wait for the repsonse (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        int response = sd.write(0xFF);
+        if (!(response & 0x80)) {
+            ssel= 1;
+            sd.write(0xFF);
+            return response;
+        }
+    }
+    ssel = 1;
+    sd.write(0xFF);
+    return -1; // timeout
+}
+
+
+int initialise_card_v1() {
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        cmd(55, 0);
+        if (cmd(41, 0) == 0) {
+            cdv = 512;
+            debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
+            return SDCARD_V1;
+        }
+    }
+
+    debug("Timeout waiting for v1.x card\n");
+    return SDCARD_FAIL;
+}
+
+int initialise_card_v2() {
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        wait_ms(50);
+        cmd58();
+        cmd(55, 0);
+        if (cmd(41, 0x40000000) == 0) {
+            cmd58();
+            debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
+            cdv = 1;
+            return SDCARD_V2;
+        }
+    }
+
+    debug("Timeout waiting for v2.x card\n");
+    return SDCARD_FAIL;
+}
+
+
+int initialise_card() {
+    // Set to SCK for initialisation, and clock card with cs = 1
+    sd.frequency(100000);
+    ssel = 1;
+    for (int i = 0; i < 16; i++) {
+        sd.write(0xFF);
+    }
+
+    // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
+    if (cmd(0, 0) != R1_IDLE_STATE) {
+        debug("No disk, or could not put SD card in to SPI idle state\n");
+        return SDCARD_FAIL;
+    }
+
+    // send CMD8 to determine whther it is ver 2.x
+    int r = cmd8();
+    if (r == R1_IDLE_STATE) {
+        return initialise_card_v2();
+    } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
+        return initialise_card_v1();
+    } else {
+        debug("Not in idle state after sending CMD8 (not an SD card?)\n");
+        return SDCARD_FAIL;
+    }
+}
+
+
+int cmd8() {
+    ssel = 0;
+
+    // send a command
+    sd.write(0x40 | 8); // CMD8
+    sd.write(0x00);     // reserved
+    sd.write(0x00);     // reserved
+    sd.write(0x01);     // 3.3v
+    sd.write(0xAA);     // check pattern
+    sd.write(0x87);     // crc
+
+    // wait for the repsonse (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
+        char response[5];
+        response[0] = sd.write(0xFF);
+        if (!(response[0] & 0x80)) {
+            for (int j = 1; j < 5; j++) {
+                response[i] = sd.write(0xFF);
+            }
+            ssel = 1;
+            sd.write(0xFF);
+            return response[0];
+        }
+    }
+    ssel = 1;
+    sd.write(0xFF);
+    return -1; // timeout
+}
+
+
+int cmd58() {
+    ssel = 0;
+    int arg = 0;
+
+    // send a command
+    sd.write(0x40 | 58);
+    sd.write(arg >> 24);
+    sd.write(arg >> 16);
+    sd.write(arg >> 8);
+    sd.write(arg >> 0);
+    sd.write(0x95);
+
+    // wait for the repsonse (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        int response = sd.write(0xFF);
+        if (!(response & 0x80)) {
+            int ocr = sd.write(0xFF) << 24;
+            ocr |= sd.write(0xFF) << 16;
+            ocr |= sd.write(0xFF) << 8;
+            ocr |= sd.write(0xFF) << 0;
+            ssel = 1;
+            sd.write(0xFF);
+            return response;
+        }
+    }
+    ssel = 1;
+    sd.write(0xFF);
+    return -1; // timeout
+}
\ No newline at end of file