Change cfgMqttWattJson parsing to be more flexible

Author: steff393

src/mqtt.cpp

@@ -1,7 +1,6 @@
 // Copyright (c) 2021 steff393, MIT license
 
 #include <Arduino.h>
-#include <ArduinoJson.h>
 #include <ESP8266WiFi.h>
 #include <globalConfig.h>
 #include <inverter.h>
@@ -12,9 +11,6 @@
 #include <pvAlgo.h>
 
 
-#define MAX_JSON_LEN        200
-
-
 const uint8_t m = 2;
 
 WiFiClient espClient;
@@ -104,15 +100,13 @@ void callback(char* topic, byte* payload, uint8_t length)
 			// directly take the value from the buffer
 			pv_setWatt(atol(buffer));
 		} else {
-			// extract the value from a JSON string
-			StaticJsonDocument<MAX_JSON_LEN> doc;
-			// Parse JSON object
-			DeserializationError error = deserializeJson(doc, buffer);
-			if (error) {
-				LOG(m, "deserializeJson() failed: %s", error.f_str())
-			} else {
-				pv_setWatt((long) doc[cfgMqttWattJson].as<float>());
-			}
+			// extract the value from a JSON string (only 1st occurence)
+			// Example: {"Time":"2022-12-10T17:25:46","Main":{"power":-123,"from_grid":441.231,"to_grid":9578.253}}
+			// cfgMqttWattJson = power\":                      |      |------>
+			// the slash \ will escape the quote " sign
+			char * pch;
+			pch = strstr(buffer, cfgMqttWattJson) + strlen(cfgMqttWattJson); // search the index of cfgMqttWattJson, then add it's length
+			pv_setWatt(atol(pch));
 		}
 	}