SRAM::Stream::write, performance optimization

Author: mikaelpatel

examples/Stream/Stream.ino

@@ -23,7 +23,7 @@ SRAM<BOARD::D10>::Stream<10000> temps(sram, 10000);
 
 const int N = 1000;
 int count = 0;
-uint32_t s0, m0, m1, m2, m3, m4, m5;
+uint32_t s0, m0, m1, m2, m3, m4, m5, m6, m7;
 
 void setup()
 {
@@ -39,8 +39,8 @@ void loop()
     Serial.println(analogRead(A0));
   }
   Serial.println();
-  m0 = micros() - s0;
   Serial.flush();
+  m0 = micros() - s0;
 
   // Print N analog samples to sram stream
   s0 = micros();
@@ -61,6 +61,7 @@ void loop()
   s0 = micros();
   while (temps.available())
     Serial.write(temps.read());
+  Serial.flush();
   m3 = micros() - s0;
 
   // Write to sram stream
@@ -74,12 +75,31 @@ void loop()
   for (int i = 0; i < count; i++) sum += ios.read();
   m5 = micros() - s0;
 
+  // Write N analog samples to sram stream
+  s0 = micros();
+  int sample;
+  for (int i = 0; i < N; i++) {
+    sample = analogRead(A0);
+    ios.write((const uint8_t*) &sample, sizeof(sample));
+  }
+  m6 = micros() - s0;
+
+  // Read N analog samples from sram stream and print to serial
+  s0 = micros();
+  while (ios.available()) {
+    ios.readBytes((uint8_t*) &sample, sizeof(sample));
+    Serial.println(sample);
+  }
+  Serial.flush();
+  m7 = micros() - s0;
+
   Serial.print(F("Samples, N = "));
   Serial.println(N);
   Serial.print(F("Serial.print, m0 = "));
   Serial.println(m0 / N);
   Serial.print(F("SRAM::Stream.print, m1 = "));
   Serial.println(m1 / N);
+  Serial.println();
   Serial.print(F("SRAM::Stream.available, count = "));
   Serial.println(count);
   Serial.print(F("SRAM::Stream.write/read, m2 = "));
@@ -90,6 +110,14 @@ void loop()
   Serial.println(m4 / count);
   Serial.print(F("SRAM::Stream.read, m5 = "));
   Serial.println(m5 / count);
+  Serial.println();
+  Serial.print(F("SRAM::Stream.available, N*2 = "));
+  Serial.println(N * 2);
+  Serial.print(F("SRAM::Stream.write(2), m6 = "));
+  Serial.println(m6 / N);
+  Serial.print(F("SRAM::Stream.read(2)/Serial.print, m7 = "));
+  Serial.println(m7 / N);
+  Serial.println();
 
   delay(1000);
 }

src/Driver/SRAM.h

@@ -125,6 +125,34 @@ class SRAM : protected SPI::Device<0, MSBFIRST, FREQ, SS_PIN> {
       return (sizeof(byte));
     }
 
+    /**
+     * @override{Stream}
+     * Write given buffer and numbe of bytes to stream. Return number
+     * of bytes written.
+     * @param[in] bufffer to write.
+     * @param[in] size number of byets to write.
+     * @return number of bytes.
+     */
+    virtual size_t write(const uint8_t *buffer, size_t size)
+    {
+      uint16_t room = SIZE - m_count;
+      if (room == 0) return (0);
+      if (size > room) size = room;
+      size_t res = size;
+      room = SIZE - m_put;
+      if (size > room) {
+	m_sram.write(m_addr + m_put, buffer, room);
+	buffer += room;
+	size -= room;
+	m_count += room;
+	m_put = 0;
+      }
+      m_sram.write(m_addr + m_put, buffer, size);
+      m_count += size;
+      m_put += size;
+      return (res);
+    }
+
     /**
      * @override{Stream}
      * Returns number of bytes available for read().