Improved data carrier detection

device.h

@@ -9,7 +9,7 @@
 #define FREQUENCY_CORRECTION 0
 
 // ADC settings
-#define OPEN_SQUELCH false
+#define OPEN_SQUELCH true
 #define ADC_REFERENCE REF_3V3
 // OR
 //#define ADC_REFERENCE REF_5V

hardware/AFSK.c

@@ -205,6 +205,14 @@ static bool hdlcParse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo) {
             // on the RX LED.
             fifo_push(fifo, HDLC_FLAG);
             hdlc->receiving = true;
+
+            if (hdlc->dcd_count < DCD_MIN_COUNT) {
+                hdlc->dcd = false;
+                hdlc->dcd_count++;
+            } else {
+                hdlc->dcd = true;
+            }
+
             #if OPEN_SQUELCH == false
                 LED_RX_ON();
             #endif
@@ -215,7 +223,8 @@ static bool hdlcParse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo) {
             
             ret = false;
             hdlc->receiving = false;
-            LED_RX_OFF();
+            hdlc->dcd = false;
+            hdlc->dcd_count = 0;
         }
 
         // Everytime we receive a HDLC_FLAG, we reset the
@@ -239,10 +248,18 @@ static bool hdlcParse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo) {
         // If we have, something probably went wrong at the
         // transmitting end, and we abort the reception.
         hdlc->receiving = false;
-        LED_RX_OFF();
+        hdlc->dcd = false;
+        hdlc->dcd_count = 0;
         return ret;
     }
 
+    // Check the DCD status and set RX LED appropriately
+    if (hdlc->dcd) {
+        LED_RX_ON();
+    } else {
+        LED_RX_OFF();
+    }
+
     // If we have not yet seen a HDLC_FLAG indicating that
     // a transmission is actually taking place, don't bother
     // with anything.

hardware/AFSK.h

@@ -52,6 +52,8 @@ inline static uint8_t sinSample(uint16_t i) {
 #define SAMPLESPERBIT (SAMPLERATE / BITRATE)
 #define PHASE_INC    1                              // Nudge by an eigth of a sample each adjustment
 
+#define DCD_MIN_COUNT 6
+                       
 #if BITRATE == 960
     #define FILTER_CUTOFF 600
     #define MARK_FREQ  960
@@ -80,6 +82,8 @@ typedef struct Hdlc
     uint8_t bitIndex;
     uint8_t currentByte;
     bool receiving;
+    bool dcd;
+    uint8_t dcd_count;
 } Hdlc;
 
 typedef struct Afsk

protocol/KISS.c

@@ -49,7 +49,7 @@ void kiss_csma(AX25Ctx *ctx, uint8_t *buf, size_t len) {
     bool sent = false;
     while (!sent) {
         //puts("Waiting in CSMA");
-        if(!channel->hdlc.receiving) {
+        if(!channel->hdlc.dcd) {
             uint8_t tp = rand() & 0xFF;
             if (tp < p) {
                 ax25_sendRaw(ctx, buf, len);