Ignore JSON enabled setting on nRF52 platforms (#3286)

Not supported, see #2804

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/mqtt/MQTT.cpp

@@ -351,11 +351,13 @@ void MQTT::sendSubscriptions()
             std::string topic = cryptTopic + channels.getGlobalId(i) + "/#";
             LOG_INFO("Subscribing to %s\n", topic.c_str());
             pubSub.subscribe(topic.c_str(), 1); // FIXME, is QOS 1 right?
+#ifndef ARCH_NRF52                              // JSON is not supported on nRF52, see issue #2804
             if (moduleConfig.mqtt.json_enabled == true) {
                 std::string topicDecoded = jsonTopic + channels.getGlobalId(i) + "/#";
                 LOG_INFO("Subscribing to %s\n", topicDecoded.c_str());
                 pubSub.subscribe(topicDecoded.c_str(), 1); // FIXME, is QOS 1 right?
             }
+#endif // ARCH_NRF52
         }
     }
 #endif
@@ -450,6 +452,7 @@ void MQTT::publishQueuedMessages()
 
         publish(topic.c_str(), bytes, numBytes, false);
 
+#ifndef ARCH_NRF52 // JSON is not supported on nRF52, see issue #2804
         if (moduleConfig.mqtt.json_enabled) {
             // handle json topic
             auto jsonString = this->meshPacketToJson(env->packet);
@@ -460,6 +463,7 @@ void MQTT::publishQueuedMessages()
                 publish(topicJson.c_str(), jsonString.c_str(), false);
             }
         }
+#endif // ARCH_NRF52
         mqttPool.release(env);
     }
 }
@@ -504,6 +508,7 @@ void MQTT::onSend(const meshtastic_MeshPacket &mp, const meshtastic_MeshPacket &
 
             publish(topic.c_str(), bytes, numBytes, false);
 
+#ifndef ARCH_NRF52 // JSON is not supported on nRF52, see issue #2804
             if (moduleConfig.mqtt.json_enabled) {
                 // handle json topic
                 auto jsonString = this->meshPacketToJson((meshtastic_MeshPacket *)&mp_decoded);
@@ -514,7 +519,7 @@ void MQTT::onSend(const meshtastic_MeshPacket &mp, const meshtastic_MeshPacket &
                     publish(topicJson.c_str(), jsonString.c_str(), false);
                 }
             }
-
+#endif // ARCH_NRF52
         } else {
             LOG_INFO("MQTT not connected, queueing packet\n");
             if (mqttQueue.numFree() == 0) {