Diff: main.cpp

Revision:

0:780646889745

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Jan 15 17:27:09 2013 +0000
@@ -0,0 +1,170 @@
+#include "mbed.h"
+#include "sin_table.hpp"
+#include "varicode_table.hpp"
+
+DigitalOut myled(LED2);
+DigitalOut port21(p21);
+AnalogOut signal(p18);
+
+Ticker lifepulse;
+//Serial pc(USBTX, USBRX); // tx, rx
+
+
+int deltaPhase;
+double Ic, Qc, I, Q, bpsk;
+double Ai                    = 1.0;                      // Next symbol phase
+double Aq                    = 1.0;  
+
+//const float Fc              = 400.0;                    // Carrier frequency in Hertz
+//const float Fs              = 31.25;                    // Symbol frequency in Hertz
+const float Tick_us         = 100.0;                    // Tick period in microseconds
+//const float Tc              = (1/Fc);                   // Carrier signal period in seconds
+//const float Ts              = (1/Fs);                   // Symbol signal period in seconds
+
+double As                    = 0.001;
+
+int SymbolCycles            = 320;
+int HalfSymbolCycles        = 160;
+int Cycles                  = 0;                        // Keep track of cycles for symbol coding
+int SymbolTick              = 0;
+int SymbolDeltaPhase        = 0;
+
+char Message[] = " Welcome to mbed PSK31 beacon! ";
+int MsgPtr = 0;
+int  SymbolBitPos = 0;  // 15 positions
+int  Zeros = 0;
+int  ChangePhase = 0;
+int  SendZeros = 60;
+
+void get_next_symbol (void) 
+{
+    if (Message[MsgPtr] == NULL) {
+        MsgPtr = 0;
+        Zeros = 0;
+        SymbolBitPos = 0;
+    }
+    if (SymbolBitPos == 16) {
+        SymbolBitPos = 0;
+    }
+    
+    if (((varicode[Message[MsgPtr]] << SymbolBitPos)&0x8000) == 0) {
+        if (Ai > 0) {
+            Ai = -1.0;
+            Aq = -1.0;
+        }
+        else {
+            Ai = 1.0;
+            Aq = 1.0;
+        }
+        
+        ChangePhase = 1;
+        Zeros++;
+        if (Zeros == 2) {
+            MsgPtr++;
+            Zeros = 0;
+            SymbolBitPos = 0;
+        }
+        else        
+            SymbolBitPos++;
+    }
+    else {
+        ChangePhase = 0;
+        Zeros = 0;
+        SymbolBitPos++;
+    }
+}
+
+void genpsk31() {
+    
+    signal = bpsk;
+
+    // ==============================================================================
+    // Carrier Frequency Part
+    // ==============================================================================
+    Ic = SIN[deltaPhase];
+    Qc = COS[deltaPhase];
+
+    deltaPhase++;
+    if (deltaPhase == SIN_TABLE_SIZE) {
+        deltaPhase = 0;
+    }
+
+    // ==============================================================================
+    // Symbol Part
+    // ==============================================================================
+    
+    // Is this end of BPSK period?
+    if (Cycles == 0) {                          // Start of symbol period
+        if (SendZeros) { 
+            SendZeros--;     
+            if (I < 0) {
+                Ai = -1.0;
+                Aq = -1.0;
+            }
+            else {
+                Ai = 1.0;
+                Aq = 1.0;
+            }
+            ChangePhase = 1;
+        }
+        else
+            get_next_symbol();
+    }
+    
+    if ((Cycles < HalfSymbolCycles)&&(ChangePhase==1)) {            // Transition to next phase
+        I = Ai*SIN[SymbolDeltaPhase];
+        Q = Aq*SIN[SymbolDeltaPhase];
+    }
+    else {
+        if (I<0) I = Q = -1;
+        else     I = Q =  1;
+    }
+    
+
+    SymbolTick++;
+    if (SymbolTick == 13) {
+        SymbolTick = 0;
+        SymbolDeltaPhase++;
+        if (SymbolDeltaPhase == 20) SymbolDeltaPhase = 6;
+    }
+           
+    Cycles++;
+    if (Cycles == SymbolCycles) {
+        if (port21) port21=0; else port21=1;
+        //port21 = 1;
+        Cycles = 0;    
+        SymbolTick = 0;
+        SymbolDeltaPhase = 6;
+    }
+        
+    // ==============================================================================
+    // Calculate BPSK
+    // ==============================================================================
+    bpsk = As*(I*Ic + Q*Qc) + 0.5;
+
+    //port21 = 0;
+}
+
+
+
+int main() {
+    deltaPhase = 0;
+    Cycles = 0;
+    I = 1.0;
+    Q = 1.0;
+    Ic = 1.0;
+    Qc = 1.0;
+    port21 = 0;
+    lifepulse.attach_us(&genpsk31,Tick_us); 
+
+    while(1) {
+        myled = 1;
+        wait(0.2);
+        myled = 0;
+        wait(0.2);
+        //pc.printf("Hello World!\n\r");
+
+    }
+}
+
+