Add isValid

Add isValid function to checks if the buffer is a CayenneLPP valid payload.

Author: ricaun

docs/CayenneLPPDecode.md

@@ -40,5 +40,11 @@ Decode buffer to the JsonObject root, check [ArduinoJson](https://github.com/bbl
 void decode(JsonObject &root);
 ```
 
+## Method: `isValid`
 
+This function checks if the buffer is a CayenneLPP valid payload.
+
+```c
+bool isValid();
+```
 

examples/Decode/Decode.ino

@@ -12,7 +12,8 @@
 
 #include <CayenneLPPDecode.h>
 
-void setup() {
+void setup()
+{
   DynamicJsonDocument jsonBuffer(512);
   CayenneLPP lpp(64);
   CayenneLPPDecode lppd;
@@ -37,12 +38,14 @@ void setup() {
   lpp.addGPS(1, -12.34f, 45.56f, 9.01f);
 
   lppd.write(lpp.getBuffer(), lpp.getSize());
-
-  lppd.decode(root);
-  serializeJsonPretty(root ,Serial);
-  Serial.println();
+  if (lppd.isValid())
+  {
+    lppd.decode(root);
+    serializeJsonPretty(root, Serial);
+    Serial.println();
+  }
 }
 
-void loop() {
-
+void loop()
+{
 }

examples/DecodeLoRaDuplex/DecodeLoRaDuplex.ino

@@ -88,13 +88,16 @@ void onReceive(int packetSize) {
     lppd.write(LoRa.read());
   }
 
-  lppd.decode(root);
-
   Serial.print("Receive: ");
   Serial.println();
 
-  serializeJsonPretty(root ,Serial);
-  Serial.println();
+  if (lppd.isValid())
+  {
+    lppd.decode(root);
+
+    serializeJsonPretty(root, Serial);
+    Serial.println();
+  }
 }
 
 boolean runEvery(unsigned long interval)

keywords.txt

@@ -30,6 +30,7 @@ addBarometricPressure	KEYWORD2
 addGyrometer	KEYWORD2
 addGPS	KEYWORD2
 
+isValid	KEYWORD2
 decode	KEYWORD2
 dumpBuffer	KEYWORD2
 

library.properties

@@ -1,5 +1,5 @@
 name=CayenneLPPDecode
-version=1.0.2
+version=1.0.3
 author=Luiz Henrique Cassettari & The Things Network
 maintainer=Luiz Henrique Cassettari <ricaun@gmail.com>
 sentence=Decode CayenneLPP to Json format as TTN.

src/CayenneLPPDecode.cpp

@@ -99,6 +99,63 @@ void CayenneLPPDecode::reset(void)
     payload_position = 0;
 }
 
+bool CayenneLPPDecode::isValid()
+{
+    int i = 0;
+    int len = payload_length;
+    if (len < 2)
+        return false;
+
+    while (i < len)
+    {
+        int channel = payload_buffer[i];
+        int type = payload_buffer[i + 1];
+        switch (type)
+        {
+        case LPP_DIGITAL_INPUT:
+        case LPP_DIGITAL_OUTPUT:
+            i += LPP_DIGITAL_OUTPUT_SIZE;
+            break;
+        case LPP_ANALOG_INPUT:
+        case LPP_ANALOG_OUTPUT:
+            i += LPP_ANALOG_OUTPUT_SIZE;
+            break;
+        case LPP_LUMINOSITY:
+            i += LPP_LUMINOSITY_SIZE;
+            break;
+        case LPP_PRESENCE:
+            i += LPP_PRESENCE_SIZE;
+            break;
+        case LPP_TEMPERATURE:
+            i += LPP_TEMPERATURE_SIZE;
+            break;
+        case LPP_RELATIVE_HUMIDITY:
+            i += LPP_RELATIVE_HUMIDITY_SIZE;
+            break;
+        case LPP_ACCELEROMETER:
+            i += LPP_ACCELEROMETER_SIZE;
+            break;
+        case LPP_BAROMETRIC_PRESSURE:
+            i += LPP_BAROMETRIC_PRESSURE_SIZE;
+            break;
+        case LPP_GYROMETER:
+            i += LPP_GYROMETER_SIZE;
+            break;
+        case LPP_GPS:
+            i += LPP_GPS_SIZE;
+            break;
+        default:
+            return false;
+            break;
+        }
+    }
+
+    if (i > len)
+        return false;
+
+    return true;
+}
+
 void CayenneLPPDecode::decode(JsonObject &_root)
 {
     JsonObject &root = (JsonObject &)_root;

src/CayenneLPPDecode.h

@@ -41,6 +41,7 @@ class CayenneLPPDecode : public Stream
   void decode(JsonObject &_root);
 
   void reset();
+  bool isValid();
 
 private:
   virtual int available();