Revision 0:96c89b4dc711, committed 2020-12-08

Comitter:

villemejane

Date:

Tue Dec 08 12:10:01 2020 +0000

Child:

1:76fbb91a0331

Child:

2:47d90ce030a3

Commit message:

Calcul de FFT sur 256 points

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Dec 08 12:10:01 2020 +0000
@@ -0,0 +1,66 @@
+#include "mbed.h"
+#include "arm_math.h"
+/* Include mbed-dsp libraries */
+#include "dsp.h"
+#include "arm_common_tables.h"
+#include "arm_const_structs.h"
+
+#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 */
+ 
+float32_t Input[SAMPLES];
+float32_t Output[FFT_SIZE];
+bool      trig=0;
+int       indice = 0;
+
+DigitalOut myled(LED1);
+AnalogIn   myADC(A0);
+AnalogOut  myDAC(A2);
+Serial     pc(USBTX, USBRX);
+Ticker     timer;
+ 
+void sample(){
+    myled = 1;
+    if(indice < SAMPLES){
+        Input[indice] = myADC.read() - 0.5f;    //Real part NB removing DC offset
+        Input[indice + 1] = 0;                  //Imaginary Part set to zero
+        indice += 2;
+    }
+    else{ trig = 0; }
+    myled = 0;
+}
+ 
+int main() {
+    float maxValue;            // Max FFT value is stored here
+    uint32_t maxIndex;         // Index in Output array where max value is
+
+    while(1) {
+        if(trig == 0){
+            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);
+            Output[0] = 0;
+            //Calculates maxValue and returns corresponding value
+            arm_max_f32(Output, FFT_SIZE/2, &maxValue, &maxIndex);
+        
+            myDAC=1.0;     //SYNC Pulse to DAC Output
+            wait_us(20);    //Used on Oscilliscope set trigger level to the highest
+            myDAC=0.0;     //point on this pulse 
+    
+            for(int i=0; i < FFT_SIZE / 2; i++){
+                myDAC=(Output[i]) * 0.9;   // Scale to Max Value and scale to 90 / 100
+                wait_us(10);                //Each pulse of 10us is 50KHz/256 = 195Hz resolution
+            }
+            myDAC=0.0;
+            pc.printf("MAX = %lf, %d \r\n", maxValue, maxIndex);
+            wait(0.2);
+            trig = 1;
+            indice = 0;
+            timer.attach_us(&sample,40);      //20us 50KHz sampling rate
+        }
+    }
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-dsp.lib	Tue Dec 08 12:10:01 2020 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/users/mbed_official/code/mbed-dsp/#3762170b6d4d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Tue Dec 08 12:10:01 2020 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/users/mbed_official/code/mbed/builds/65be27845400
\ No newline at end of file