Testing SD card

TestPrograms/SDCardSpeedTest/SDCardSpeedTest.ino

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+/*
+ * This sketch is a simple binary write/read benchmark.
+ */
+#include <SdFat.h>
+#include <SdFatUtil.h>
+
+// SD chip select pin
+const uint8_t chipSelect = BUILTIN_SDCARD;
+
+#define FILE_SIZE_MB 5
+#define FILE_SIZE (1000000UL*FILE_SIZE_MB)
+#define BUF_SIZE 100
+
+uint8_t buf[BUF_SIZE];
+
+// file system
+SdFat sd;
+
+// test file
+SdFile file;
+
+// Serial output stream
+ArduinoOutStream cout(Serial);
+//------------------------------------------------------------------------------
+// store error strings in flash to save RAM
+#define error(s) sd.errorHalt_P(PSTR(s))
+//------------------------------------------------------------------------------
+void setup() {
+  Serial.begin(9600);
+  while (!Serial){}  // wait for Leonardo
+  Serial.println();
+}
+//------------------------------------------------------------------------------
+void loop() {
+  uint32_t maxLatency;
+  uint32_t minLatency;
+  uint32_t totalLatency;
+
+  // discard any input
+  while (Serial.read() >= 0) {}
+
+  // pstr stores strings in flash to save RAM
+  cout << pstr("Type any character to start\n");
+  while (Serial.read() <= 0) {}
+  delay(400);  // catch Due reset problem
+  
+  cout << pstr("Free RAM: ") << FreeRam() << endl;
+
+  // initialize the SD card at SPI_FULL_SPEED for best performance.
+  // try SPI_HALF_SPEED if bus errors occur.
+  if (!sd.begin(chipSelect, SPI_FULL_SPEED)) sd.initErrorHalt();
+
+  cout << pstr("Type is FAT") << int(sd.vol()->fatType()) << endl;
+
+  // open or create file - truncate existing file.
+  if (!file.open("BENCH.DAT", O_CREAT | O_TRUNC | O_RDWR)) {
+    error("open failed");
+  }
+
+  // fill buf with known data
+  for (uint16_t i = 0; i < (BUF_SIZE-2); i++) {
+    buf[i] = 'A' + (i % 26);
+  }
+  buf[BUF_SIZE-2] = '\r';
+  buf[BUF_SIZE-1] = '\n';
+
+  cout << pstr("File size ") << FILE_SIZE_MB << pstr("MB\n");
+  cout << pstr("Buffer size ") << BUF_SIZE << pstr(" bytes\n");
+  cout << pstr("Starting write test.  Please wait up to a minute\n");
+
+  // do write test
+  uint32_t n = FILE_SIZE/sizeof(buf);
+  maxLatency = 0;
+  minLatency = 9999999;
+  totalLatency = 0;
+  uint32_t t = millis();
+  for (uint32_t i = 0; i < n; i++) {
+    uint32_t m = micros();
+    if (file.write(buf, sizeof(buf)) != sizeof(buf)) {
+      error("write failed");
+    }
+    m = micros() - m;
+    if (maxLatency < m) maxLatency = m;
+    if (minLatency > m) minLatency = m;
+    totalLatency += m;
+  }
+  file.sync();
+  t = millis() - t;
+  double s = file.fileSize();
+  cout << pstr("Write ") << s/t << pstr(" KB/sec\n");
+  cout << pstr("Maximum latency: ") << maxLatency;
+  cout << pstr(" usec, Minimum Latency: ") << minLatency;
+  cout << pstr(" usec, Avg Latency: ") << totalLatency/n << pstr(" usec\n\n");
+  cout << pstr("Starting read test.  Please wait up to a minute\n");
+  // do read test
+  file.rewind();
+  maxLatency = 0;
+  minLatency = 9999999;
+  totalLatency = 0;
+  t = millis();
+  for (uint32_t i = 0; i < n; i++) {
+    buf[BUF_SIZE-1] = 0;
+    uint32_t m = micros();
+    if (file.read(buf, sizeof(buf)) != sizeof(buf)) {
+      error("read failed");
+    }
+    m = micros() - m;
+    if (maxLatency < m) maxLatency = m;
+    if (minLatency > m) minLatency = m;
+    totalLatency += m;
+    if (buf[BUF_SIZE-1] != '\n') {
+      error("data check");
+    }
+  }
+  t = millis() - t;
+  cout << pstr("Read ") << s/t << pstr(" KB/sec\n");
+  cout << pstr("Maximum latency: ") << maxLatency;
+  cout << pstr(" usec, Minimum Latency: ") << minLatency;
+  cout << pstr(" usec, Avg Latency: ") << totalLatency/n << pstr(" usec\n\n");
+  cout << pstr("Done\n\n");
+  file.close();
+}