Merge branch 'master' of ichibi:/home/git/Repositories/pato-z80-home-computer

prototiping-with-arduino/sdcard-test/sdcard-test.ino

@@ -0,0 +1,143 @@
+/**
+ * SPI SD-Card test sketch
+ * Reads the first 128 bytes from sdcard and prints it out as ascii characters in serial monitor at 9200 baud
+ * 
+ * Implementation of the specification at http://elm-chan.org/docs/mmc/mmc_e.html
+ */
+
+#define CS 5    // aka CAT3
+#define MOSI 4  // aka DI or CMD
+#define SCK 3   // aka CAT3
+#define MISO 2  // aka DAT0
+
+void setup() {
+  pinMode(CS, OUTPUT);
+  pinMode(MOSI, OUTPUT);
+  pinMode(SCK, OUTPUT);
+  pinMode(MISO, INPUT);
+
+  Serial.begin(9600);
+
+  /***** Init sequence *******/
+
+  // Wait 1ms
+  delay(1);
+
+  Serial.println("Init card...");
+
+
+  // >= 75 clocks with CS and DI high
+  digitalWrite(CS, HIGH);
+  digitalWrite(MOSI, HIGH);
+  for (byte i=0; i<80; i++) {
+    clk();
+  }
+
+  // CMD0 with CS low (Software reset). Means "Leave native mode and enter SPI mode"
+  digitalWrite(CS, LOW);
+  byte arg[] = {0x00,0x00,0x00,0x00};
+  sendCommand(B01000000, arg); // First two bits are always 01. Command is 0 (000000).
+  byte resp = receiveResponse();
+  Serial.print("    CMD0 response: ");
+  Serial.println(resp, HEX);
+  // Now card is in idle mode
+
+  // Send CMD8 (check voltage) to find if sd version is 2 or previous
+  byte arg2[] = {0x00,0x00,0x00,0x00};
+  sendCommand(B01001000, arg2); // CMD8
+  resp = receiveResponse();
+  Serial.print("    CMD8 response: ");
+  Serial.println(resp, HEX);
+
+  if (resp == 5) {
+    // CMD8 Illegal command: sd version 1.X
+
+    while(true) {
+      // Now send ACMD41. ACMD is a CMD55 followed by a CMDxx
+      byte arg3[] = {0x00,0x00,0x00,0x00};
+      sendCommand(B01110111, arg3); // CMD55
+      //resp = receiveResponse();
+      Serial.print("    CMD55 response: ");
+      Serial.println(resp, HEX);
+      byte arg4[] = {0x40,0x00,0x00,0x00};
+      sendCommand(B01101001, arg4); // CMD41
+      resp = receiveResponse();
+      Serial.print("    CMD41 response: ");
+      Serial.println(resp, HEX);
+    }
+  } else {
+    Serial.print("Sd version 2 not supported.");
+  }
+  
+  
+  digitalWrite(CS, HIGH);
+
+}
+
+void loop() {}
+
+/**
+ * Sends a clock cycle
+ */
+void clk() {
+  digitalWrite(SCK, HIGH);
+  //delayMicroseconds(1);
+  digitalWrite(SCK, LOW);
+  //delayMicroseconds(1);
+}
+
+/**
+ * Sends a command to card.
+ * The sent CRC field is valid for the CMD0 message.
+ * This is ok, since the CRC field will not be checked in SPI mode.
+ * @param index: the command index byte. First two bytes are the sync bytes "01".
+ */
+void sendCommand(byte index, byte arg[]) {
+  // Send command index (2+6=8 bits)
+  sendByte(index);
+  // Send argument (32 bit)
+  for(byte i=0; i<4; i++) {
+    sendByte(arg[i]);
+  }
+  // Send CRC with final stop bit (7+1=8 bits)
+  sendByte(B10010101);  // We send always the CMD0 CRC, because is not checked in SPI mode
+}
+
+/**
+ * Sends a byte to the card. The two MSB must be 01 as per specification.
+ * Byte is sent MSB first.
+ */
+void sendByte(byte b) {
+  for (byte i=0; i<8; i++) {
+    // If last bit is 1 set MOSI HIGH, else LOW
+    digitalWrite(MOSI, (b & B10000000) == B10000000 ? HIGH : LOW);
+    //Serial.print((b & B10000000) == B10000000 ? "1" : "0");
+    clk();
+    // Shift byte to have, in the next cycle, the next bit in last position
+    b = b << 1;
+  }
+}
+
+/**
+ * Receives the response from card
+ * MSB first.
+ */
+byte receiveResponse() {
+  digitalWrite(CS, LOW);
+  digitalWrite(MOSI, HIGH);
+  
+  // continuously toggle the SD CLK signal and observe the MISO line for data:
+  // message response starts with 0
+  while (digitalRead(MISO)) {
+    clk();
+  }  // Wait for first 0
+
+  byte resp = 0;
+  // Read 8 bits
+  for (byte i=0; i<8; i++) {
+    resp = resp << 1;
+    resp = resp | digitalRead(MISO);
+    clk();
+  }
+  return resp;
+}