Removed moving average filtering from MDx ADC1 driver, added code for proper filtering of ADC samples in platform-independent code

openrtx/src/rtx.c

@@ -34,6 +34,8 @@ rtxStatus_t rtxStatus;  /* RTX driver status                  */
 bool sqlOpen;           /* Flag for squelch open/close        */
 bool enterRx;           /* Flag for RX mode activation        */
 
+float rssi;             /* Current RSSI in dBm                */
+
 /*
  * These functions below provide a basic API for audio path management. They
  * will be removed once the audio driver is set up.
@@ -134,6 +136,11 @@ void rtx_init(OS_MUTEX *m)
      */
     radio_init();
 
+    /*
+     * Initial value for RSSI filter
+     */
+    rssi = radio_getRssi(rtxStatus.rxFrequency);
+
     _afCtrlInit();
 }
 
@@ -236,9 +243,12 @@ void rtx_taskFunc()
     if(rtxStatus.opStatus == RX)
     {
         /*
-         * RSSI-based squelch mechanism, with 15 levels from -140dBm to -70dBm
+         * RSSI-based squelch mechanism, with 15 levels from -140dBm to -70dBm.
+         *
+         * RSSI value is passed through a filter with a time constant of 60ms
+         * (cut-off frequency of 15Hz) at an update rate of 33.3Hz
          */
-        float rssi = rtx_getRssi();
+        rssi = 0.74*radio_getRssi(rtxStatus.rxFrequency) + 0.26*rssi;
         float squelch = -127.0f + rtxStatus.sqlLevel * 66.0f / 15.0f;
 
         if((sqlOpen == false) && (rssi > (squelch + 0.1f)))
@@ -261,6 +271,9 @@ void rtx_taskFunc()
         radio_enableRx();
         rtxStatus.opStatus = RX;
         enterRx = false;
+
+        /* Reinitialise RSSI filter state */
+        rssi = radio_getRssi(rtxStatus.rxFrequency);
     }
 
     /* TX logic */
@@ -309,5 +322,5 @@ void rtx_taskFunc()
 
 float rtx_getRssi()
 {
-    return radio_getRssi(rtxStatus.rxFrequency);
+    return rssi;
 }

openrtx/src/threads.c

@@ -251,6 +251,11 @@ static void dev_task(void *arg)
     (void) arg;
     OS_ERR os_err;
 
+    // Initialise battery voltage, to avoid filter settling transient
+    OSMutexPend(&state_mutex, 0u, OS_OPT_PEND_BLOCKING, 0u, &os_err);
+    state.v_bat = platform_getVbat();
+    OSMutexPost(&state_mutex, OS_OPT_POST_NONE, &os_err);
+
     while(1)
     {
         // Lock mutex and update internal state
@@ -260,7 +265,11 @@ static void dev_task(void *arg)
         state.time = rtc_getTime();
         state_applyTimezone();
 #endif
-        state.v_bat = platform_getVbat();
+
+        // Low-pass filtering with a time constant of 10s when updated at 1Hz
+        float vbat = platform_getVbat();
+        state.v_bat = 0.02*vbat + 0.98*state.v_bat;
+
         state.charge = battery_getCharge(state.v_bat);
         state.rssi = rtx_getRssi();
 

platform/drivers/ADC/ADC1_MDx.c

@@ -20,18 +20,12 @@
 #include "ADC1_MDx.h"
 
 /*
- * Ringbuffer of samples to allow for value smoothing through averaging. This
+ * The sample buffer is structured as follows:
- * buffer is structured as follows:
  *
- * | vbat | rssi | vox | vol | vbat | rssi | vox | vol | ...
+ * | vbat | rssi | vox | vol |
  *
- * thus it contains four samples of the four channels. Then, DMA is configured
- * in circular mode with a rollover after 16 transfers, effectively managing
- * this buffer as a ringbuffer for the measurements of the four channels.
- * Then, in adc1_getMeasurement(), the average over the values contained in the
- * ring buffer is performed and returned as the current channel value.
  */
-uint16_t sampleRingBuf[16];
+uint16_t sampleBuf[4];
 
 void adc1_init()
 {
@@ -98,8 +92,8 @@ void adc1_init()
      * - no interrupts
      */
     DMA2_Stream0->PAR = ((uint32_t) &(ADC1->DR));
-    DMA2_Stream0->M0AR = ((uint32_t) &sampleRingBuf);
+    DMA2_Stream0->M0AR = ((uint32_t) &sampleBuf);
-    DMA2_Stream0->NDTR = 16;
+    DMA2_Stream0->NDTR = 4;
     DMA2_Stream0->CR = DMA_SxCR_MSIZE_0     /* Memory size: 16 bit     */
                      | DMA_SxCR_PSIZE_0     /* Peripheral size: 16 bit */
                      | DMA_SxCR_PL_0        /* Medium priority         */
@@ -123,14 +117,6 @@ float adc1_getMeasurement(uint8_t ch)
 {
     if(ch > 3) return 0.0f;
 
-    /* Return the average over the ring buffer */
+    float value = ((float) sampleBuf[ch]);
-    float value = 0.0f;
-    for(uint8_t i = 0; i < 16; i += 4)
-    {
-        value += ((float) sampleRingBuf[i + ch]);
-    }
-    value /= 4.0f;
-
-    /* Return average value converted to mV */
     return (value * 3300.0f)/4096.0f;
 }

platform/drivers/baseband/radio_UV3x0.c

@@ -54,7 +54,7 @@ void radio_setCSS(const tone_t rxCss, const tone_t txCss)
 
 bool radio_checkRxDigitalSquelch()
 {
-
+    return false;
 }
 
 void radio_enableRx()