Diff: main.cpp

Revision:

0:05e2c9ca68e2

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Apr 13 08:59:47 2018 +0000
@@ -0,0 +1,73 @@
+#include "mbed.h"
+/* Include arm_math.h mathematic functions */
+#include "arm_math.h"
+/* Include mbed-dsp libraries */
+#include "arm_common_tables.h"
+#include "arm_const_structs.h"
+#include "math_helper.h"
+
+/* FFT settings */
+#define SAMPLES                 512             /* 256 real party and 256 imaginary parts */
+#define FFT_SIZE                SAMPLES / 2     /* FFT size is always the same size as we have samples, so 256 in our case */
+
+/* Global variables */
+float32_t Input[SAMPLES];
+float32_t Output[FFT_SIZE];
+bool      trig=0;
+/* MBED class APIs */
+DigitalOut myled(LED1);
+AnalogIn   myADC(A1);
+AnalogOut  myDAC(D13);
+Serial     pc(USBTX, USBRX);
+Ticker     timer;
+
+void sample(){
+    trig=1;
+    }
+
+int main() {
+
+    //arm_cfft_instance_f32 S;   // ARM CFFT module
+    float maxValue;            // Max FFT value is stored here
+    uint32_t maxIndex;         // Index in Output array where max value is
+    bool once=0;
+    pc.baud(115200);
+    pc.printf("Starting FFT\r\n");
+    while(1) {
+            timer.attach_us(&sample,20); //20us 50KHz sampling rate
+            for (int i = 0; i < SAMPLES; i += 2) {
+                while (trig==0){}
+                trig=0;
+                Input[i] = myADC.read() - 0.5f; //Real part NB removing DC offset
+                Input[i + 1] = 0;               //Imaginary Part set to zero
+                }
+            timer.detach();
+        // Init the Complex FFT module, intFlag = 0, doBitReverse = 1
+        //NB using predefined arm_cfft_sR_f32_lenXXX, in this case XXX is 256
+        arm_cfft_f32(&arm_cfft_sR_f32_len256, Input, 0, 1);
+
+        // Complex Magniture Module put results into Output(Half size of the Input)
+        arm_cmplx_mag_f32(Input, Output, FFT_SIZE);
+        
+        //Calculates maxValue and returns corresponding value
+        arm_max_f32(Output, FFT_SIZE, &maxValue, &maxIndex);
+
+        if (once==0){
+            pc.printf("Maximum is %f\r\n",maxValue);
+            once = 1;
+            }
+       
+        //maxValue /= 100.0f;
+        
+        myDAC=1.0f;     //SYNC Pulse to DAC Output
+        wait_us(20);    //Used on Oscilliscope set trigger level to the highest
+        myDAC=0.0f;     //point on this pulse (all FFT data will be scaled
+                        //90% of Max Value
+        
+        for (int i=0; i<FFT_SIZE/2 ; i++){
+            myDAC=(Output[i]/maxValue)*0.9f; // Scale to Max Value and scale to 90%
+            wait_us(10); //Each pulse of 10us is 50KHz/256 = 195Hz resolution
+            }
+        myDAC=0.0f;
+        }
+}
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