TX module is no longer using interrupts to read from LoRa. This fixes jumpy PPM readouts

crossbow.ino

@@ -1,11 +1,11 @@
 #define LORA_HARDWARE_SPI
 
-#define DEVICE_MODE_TX
+// #define DEVICE_MODE_TX
-// #define DEVICE_MODE_RX
+#define DEVICE_MODE_RX
 
 #define FEATURE_TX_OLED
 
-// #define DEBUG_SERIAL
+#define DEBUG_SERIAL
 // #define DEBUG_PING_PONG
 // #define DEBUG_LED
 // #define WAIT_FOR_SERIAL
@@ -20,7 +20,7 @@
 #define LORA32U4_RST_PIN    4
 #define LORA32U4_DI0_PIN    7
 
-int ppm[16] = {0};
+volatile int ppm[16] = {0};
 
 /*
  * Main defines for device working in TX mode
@@ -52,8 +52,8 @@ uint32_t lastOledTaskTime = 0;
 /*
  * Start of QSP protocol implementation
  */
-QspConfiguration_t qsp = {};
+volatile QspConfiguration_t qsp = {};
-RxDeviceState_t rxDeviceState = {};
+volatile RxDeviceState_t rxDeviceState = {};
 
 #ifdef LORA_HARDWARE_SPI
 
@@ -134,7 +134,13 @@ void setup(void)
     LoRa.setSpreadingFactor(7);
     LoRa.setCodingRate4(5);
 
+    /*
+     * Use interrupt driven approach only on RX side
+     * TX interrupts breaks PPM readout
+     */ 
+#ifdef DEVICE_MODE_RX
     LoRa.onReceive(onReceive);
+#endif
     LoRa.receive();
 #endif
 
@@ -270,9 +276,23 @@ int8_t getFrameToTransmit(QspConfiguration_t *qsp) {
 
 void loop(void)
 {
+#ifdef DEVICE_MODE_TX
+    if (LoRa.available()) {
+        qspDecodeIncomingFrame(&qsp, LoRa.read(), ppm, &rxDeviceState);
+    }
+#endif
+
     uint32_t currentMillis = millis();
     bool transmitPayload = false;
 
+#ifdef DEBUG_SERIAL
+    static uint32_t r = 0;
+    if (currentMillis - r > 1000) {
+        Serial.println(currentMillis / 1000);
+        r = currentMillis;
+    }
+#endif
+
     /*
      * Watchdog for frame decoding stuck somewhere in the middle of a process
      */
@@ -335,7 +355,7 @@ void loop(void)
             digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
         }
     }
-
+    
     /*
      * Main routine to answer to TX module
      */
@@ -432,7 +452,6 @@ void loop(void)
 
 }
 
-#ifdef LORA_HARDWARE_SPI
 void onReceive(int packetSize)
 {
     if (packetSize == 0)
@@ -442,5 +461,4 @@ void onReceive(int packetSize)
     {
         qspDecodeIncomingFrame(&qsp, LoRa.read(), ppm, &rxDeviceState);
     }
-}
+}
-#endif

qsp.cpp

@@ -142,7 +142,6 @@ void qspDecodeIncomingFrame(QspConfiguration_t *qsp, uint8_t incomingByte, int p
 
     if (qsp->protocolState == QSP_STATE_IDLE && incomingByte == QSP_PREAMBLE)
     {
-        //FIXME there should be a way to go back to IDLE if frame did not finished decoding in reasonable time
         //If in IDLE and correct preamble comes, start to decode frame
         qsp->protocolState = QSP_STATE_PREAMBLE_RECEIVED;
         qsp->crc = 0 ^ incomingByte;
@@ -177,6 +176,9 @@ void qspDecodeIncomingFrame(QspConfiguration_t *qsp, uint8_t incomingByte, int p
     }
     else if (qsp->protocolState == QSP_STATE_FRAME_TYPE_RECEIVED)
     {
+        if (receivedPayload >= QSP_PAYLOAD_LENGTH) {
+            qsp->protocolState = QSP_STATE_IDLE;
+        }
 
         //Now it's time for payload
         qsp->crc ^= incomingByte;
@@ -192,7 +194,6 @@ void qspDecodeIncomingFrame(QspConfiguration_t *qsp, uint8_t incomingByte, int p
     }
     else if (qsp->protocolState == QSP_STATE_PAYLOAD_RECEIVED)
     {
-
         if (qsp->crc == incomingByte) {
             //CRC is correct
 

variables.h

@@ -18,7 +18,7 @@
 #define QSP_PREAMBLE 0x51
 #define QSP_PAYLOAD_LENGTH 32
 
-#define QSP_MAX_FRAME_DECODE_TIME 50 //max time that frame can be decoded in ms
+#define QSP_MAX_FRAME_DECODE_TIME 10 //max time that frame can be decoded in ms
 
 #define QSP_FRAME_RC_DATA 0x0
 #define QSP_FRAME_RX_HEALTH 0x1
@@ -83,8 +83,8 @@ struct QspConfiguration_t {
 };
 
 struct RxDeviceState_t {
-    int rssi = 0;
+    uint8_t rssi = 0;
-    float snr = 0;
+    uint8_t snr = 0;
     uint8_t rxVoltage = 0;
     uint8_t a1Voltage = 0;
     uint8_t a2Voltage = 0;