Wrapping up the POC

Increased the msg buffer to allow cell voltages to be transmitted (at least Leaf). Tested OK

Software/src/battery/NISSAN-LEAF-BATTERY.cpp

@@ -1,4 +1,7 @@
 #include "NISSAN-LEAF-BATTERY.h"
+#ifdef MQTT
+#include "../devboard/mqtt/mqtt.h"
+#endif
 #include "../lib/miwagner-ESP32-Arduino-CAN/CAN_config.h"
 #include "../lib/miwagner-ESP32-Arduino-CAN/ESP32CAN.h"
 
@@ -155,6 +158,10 @@ static uint16_t temp_raw_min = 0;
 static int16_t temp_polled_max = 0;
 static int16_t temp_polled_min = 0;
 
+#ifdef MQTT
+void publish_data(void);
+#endif
+
 void print_with_units(char* header, int value, char* units) {
   Serial.print(header);
   Serial.print(value);
@@ -402,6 +409,9 @@ void update_values_leaf_battery() { /* This function maps all the values fetched
   }
 
 #endif
+#ifdef MQTT
+  publish_data();
+#endif
 }
 
 void receive_can_leaf_battery(CAN_frame_t rx_frame) {
@@ -917,3 +927,21 @@ uint16_t Temp_fromRAW_to_F(uint16_t temperature) {  //This function feels horrib
   }
   return static_cast<uint16_t>(1094 + (309 - temperature) * 2.5714285714285715);
 }
+
+#ifdef MQTT
+void publish_data(void) {
+  Serial.println("Publishing...");
+  size_t msg_length = snprintf(mqtt_msg, sizeof(mqtt_msg), "{\n\"cell_voltages\":[");
+
+  for (size_t i = 0; i < 97; ++i) {
+    msg_length += snprintf(mqtt_msg + msg_length, sizeof(mqtt_msg) - msg_length, "%s%d", (i == 0) ? "" : ",", 1234);
+    // msg_length += snprintf(mqtt_msg + msg_length, sizeof(mqtt_msg) - msg_length, "%s%d", (i == 0) ? "" : ", ", cell_voltages[i]);
+  }
+
+  snprintf(mqtt_msg + msg_length, sizeof(mqtt_msg) - msg_length, "]\n}\n");
+
+  if (mqtt_publish_retain("battery_testing/spec_data") == false) {
+    Serial.println("Nissan MQTT msg could not be sent");
+  }
+}
+#endif

Software/src/devboard/mqtt/mqtt.cpp

@@ -11,15 +11,15 @@ const size_t mqtt_nof_subscriptions = sizeof(mqtt_subscriptions) / sizeof(mqtt_s
 
 WiFiClient espClient;
 PubSubClient client(espClient);
-char msg[MSG_BUFFER_SIZE];
+char mqtt_msg[MSG_BUFFER_SIZE];
 int value = 0;
 static unsigned long previousMillisUpdateVal;
 MyTimer publish_global_timer(5000);
 
 /** Publish global values and call callbacks for specific modules */
 static void publish_values(void) {
 
-  snprintf(msg, sizeof(msg),
+  snprintf(mqtt_msg, sizeof(mqtt_msg),
            "{\n"
            "  \"SOC\": %.3f,\n"
            "  \"StateOfHealth\": %.3f,\n"
@@ -28,10 +28,14 @@ static void publish_values(void) {
            "  \"cell_max_voltage\": %d,\n"
            "  \"cell_min_voltage\": %d\n"
            "}\n",
-           ((float)SOC) / 100.0, ((float)StateOfHealth) / 100.0, ((float)((int16_t)temperature_min)) / 10.0,
-           ((float)((int16_t)temperature_max)) / 10.0, cell_max_voltage, cell_min_voltage);
-  bool result = client.publish("battery_testing/info", msg, true);
-  Serial.println(msg);  // Uncomment to print the payload on serial
+           ((float)SOC) / 100.0,
+           ((float)StateOfHealth) / 100.0,
+           ((float)((int16_t)temperature_min)) / 10.0,
+           ((float)((int16_t)temperature_max)) / 10.0,
+           cell_max_voltage,
+           cell_min_voltage);
+  bool result = client.publish("battery_testing/info", mqtt_msg, true);
+  Serial.println(mqtt_msg);  // Uncomment to print the payload on serial
 }
 
 /* This is called whenever a subscribed topic changes (hopefully) */
@@ -94,6 +98,6 @@ void mqtt_loop(void) {
   }
 }
 
-bool mqtt_publish(const String& topic, const String& payload) {
-  return client.publish(topic.c_str(), payload.c_str());
+bool mqtt_publish_retain(const char *topic) {
+  return client.publish(topic, mqtt_msg, true);
 }

Software/src/devboard/mqtt/mqtt.h

@@ -37,7 +37,7 @@
 #include <Arduino.h>
 #include "../../../USER_SETTINGS.h"
 
-#define MSG_BUFFER_SIZE (256)
+#define MSG_BUFFER_SIZE (1024)
 #define MQTT_SUBSCRIPTIONS \
   { "my/topic/abc", "my/other/topic" }
 #define MQTT_SERVER "192.168.xxx.yyy"
@@ -53,8 +53,10 @@ extern uint16_t cell_min_voltage;  //mV,   0-4350
 extern const char* mqtt_user;
 extern const char* mqtt_password;
 
+extern char mqtt_msg[MSG_BUFFER_SIZE];
+
 void init_mqtt(void);
 void mqtt_loop(void);
-bool mqtt_publish(const String& topic, const String& payload);
+bool mqtt_publish_retain(const char *topic);
 
 #endif

Software/src/lib/knolleary-pubsubclient/PubSubClient.h

@@ -23,7 +23,7 @@
 
 // MQTT_MAX_PACKET_SIZE : Maximum packet size. Override with setBufferSize().
 #ifndef MQTT_MAX_PACKET_SIZE
-#define MQTT_MAX_PACKET_SIZE 512
+#define MQTT_MAX_PACKET_SIZE 1024
 #endif
 
 // MQTT_KEEPALIVE : keepAlive interval in Seconds. Override with setKeepAlive()