Diff: main.cpp

Revision:

0:076821894a5d

Child:

1:f2da7082966e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Oct 26 19:25:24 2017 +0000
@@ -0,0 +1,55 @@
+/*
+  Project: AnalogSine (based on Nucleo_sinwave_output example)
+  File: main.cpp
+  Modified by by: Dr. C. S. Tritt
+  Last revision on: 9/26/17 (v. 1.0)
+
+  Generates sine and cosine wave forms to demonstrate D to A operation. Use a
+  data buffer for maximum speed (not necessary for 4 mS samples & 1.0 Hz 
+  signal). Output clips at a bit 0 and 3.3 V, so use AMPLITUDE <= 0.4 and 
+  OFFSET = 1.1. Zoom Horizontal scale out on MSOX2012A scopes and wait for 
+  refresh. Without wait, max. freq. (with both channels) is about 2 kHz.
+*/
+#include "mbed.h"
+
+#if !DEVICE_ANALOGOUT // Flag set by mbed.
+    #error AnalogOut is not supported on this device.  // Abort compilation.
+#else
+    AnalogOut my_Sin(PA_4); // Sine
+    AnalogOut my_Cos(PA_5); // Cosine
+    
+    const float PI = 3.14159265f; // Value of Pi for radians calculation.
+    const float AMPLITUDE = 0.4f; // x * 3.3V. D to A is limited to < 3.3 V.
+    const float OFFSET = 1.1f; // Make signal all possitive.
+    
+    // Configuration for sinewave output
+    const int BUFFER_SIZE = 250; // Elements (i.e., points).
+    float buffer[BUFFER_SIZE];
+    
+    void calculate_sinewave(void); // Fills buffer.
+    
+    int main()
+    {
+        printf("Sinewave example\n");
+        calculate_sinewave();
+        while(true) {
+            // sinewave output
+            for (int i = 0; i < BUFFER_SIZE; i++) {
+                my_Sin.write(buffer[i]); // Output a point.
+                // Generate Cosine by shifting sine by 1/4 cycle.
+                my_Cos.write(buffer[(i + BUFFER_SIZE/4) % BUFFER_SIZE]);
+                wait_ms(4); // Was wait_us(10); Remove for max. freq.
+            }
+        }
+    }
+    
+    void calculate_sinewave(void) // This function fills the buffer.
+    {
+        for (int i = 0; i < BUFFER_SIZE; i++) {
+            // Calculate radians from 0 to 2*Pi.
+            float rads = (2.0f * PI * (float) i / (float)BUFFER_SIZE);
+            // Fill the buffer.
+            buffer[i] = AMPLITUDE * (sin(rads) + OFFSET); // Sine of radians.
+        }
+    }
+#endif
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