Diff: main.cpp

Revision:

0:76eeca7a361f

diff -r 000000000000 -r 76eeca7a361f main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jan 28 12:38:34 2018 +0000
@@ -0,0 +1,90 @@
+#include "mbed.h"
+
+/*LPF cut off frequency 600Hz(3rd Order with 20kHz sampling frequency)*/
+AnalogIn Ain(p15);
+AnalogOut Aout(p18);
+
+float data_in,data_out;
+
+Ticker s1_khz_tick;
+
+__ASM int addi(int a, int b)
+{
+    ADDS R0, R1
+    BX LR
+}
+
+__ASM int multi(int a, int b)
+{
+    MUL R0, R1
+    BX LR
+}
+
+__ASM int move(int a, int b)
+{
+    MOV R0, R1
+    BX LR
+}
+
+float LPF(float LPF_in)
+{
+
+    //------------------------------FIR ----------------------------------------------------
+    float fda_coeff[16] = {0.00028360651120682420830293457569837301,
+                           0.00822761997979659653879025427158921957,
+                           0.009652502067820697279065811358123028185,
+                           -0.020505027860776389725394608376518590376,
+                           -0.055082214281865632399259880003228317946,
+                           0.001759656378417649713608028605449362658,
+                           0.187202210776797661750947554537560790777,
+                           0.369320487034980882157242376706562936306,
+                           0.369320487034980882157242376706562936306,
+                           0.187202210776797661750947554537560790777,
+                           0.001759656378417649713608028605449362658,
+                           -0.055082214281865632399259880003228317946,
+                           -0.020505027860776389725394608376518590376,
+                           0.009652502067820697279065811358123028185,
+                           0.00822761997979659653879025427158921957,
+                           0.00028360651120682420830293457569837301
+                          };
+
+    static float LPF_out;                     //the return variable/outbput of filter
+    static float x[12], y, z[12];
+
+    for (int i = 10; i >= 0; i--) {
+        x[i+1] = move(x[i+1], x[i]);
+    }
+
+    x[0] = move(x[0], LPF_in);
+
+    for (int i = 0; i < 12; i++) {
+        z[i] = multi(fda_coeff[i], x[i]);
+    }
+
+    for (int i = 0; i < 12; i++) {
+        y = addi(z[i], y);
+    }
+
+    LPF_out = move(LPF_out, y);
+    return LPF_out; //output filtered value
+}
+
+void s1khz_task(void)
+{
+    data_in = Ain - 0.5;   //Note the embed can only accept positive voltage inputs, it is necessary to add a small coupling and biasing circuit to
+    //offset the signal midway of approx 1.65V.
+    //A DC offset is a frequency component at 0 Hz. This can cause signal to wander.
+    //Therefore the mean value of the signal is subtracted.This is also to normalize the signal to an average value of zero,
+    //and allows the filter algorithm to perform DSP with no DC offset in the data.
+
+    data_out = LPF(data_in);
+    Aout = data_out + 0.5;
+}
+
+int main()
+{
+    s1_khz_tick.attach_us(&s1khz_task,1000); //1kHz sampling
+
+    while(1);
+
+}
\ No newline at end of file