Tutorial

[FernandoGarcia]

Hi @tve !

I did a tutorial to show how to set up a MQTT client to work with my controller but I think it can be useful to others users.

I spent so much time to understand how to make it work by myself so I hope it will make the life more easy to others.

Here the video:

https://youtu.be/F57SC1WOODg

Thanks for your job.

Best regards.

[ykri]

Hi @FernandoGarcia !

Great tutorial.

It was also a chance for me to go through your Freduino code and try to figure out how you did make it work with MQTT. I run a similar project with my aquarium controller and although I manage to pub/sub with the El-Client using @tve 's example, after about 10' the transmission stops and I get erroneous payloads. I cannot understand if it is that the SYNC fails, connection between Arduino and ESP is lost, or what!!! I also tried your suggestion in el-client #30 to synchronise before publish. Still after almost exactly 10' the MQTT fails.

Any ideas?

Regards,

Y.

[FernandoGarcia]

Hi!

Give more details about the error and your wiring maybe I can help you.

Try disable debug log in ESP-link web interface.

You can try the baud rate at 9600 too.

Best regards.

[ykri]

Hi @FernandoGarcia !

An ESP-01 is connected to the RxTx of the Arduino Mega. I tried 115000 and 9600 as you suggested and debug log to OFF. I run Mosquito in Linux and subscribe with NODE-RED.

When I start with MCU RESET this is the debug log output:

414278> SLIP: start or end len=64 inpkt=1 414278> cmdParsePacket: cmd=11 argc=5 value=0 414278> cmdExec: Dispatching cmd=MQTT_PUB 414278> MQTT: MQTTCMD_Publish topic=/Aquarium/Temperature1, data_len=5, qos=0, retain=0 414279> MQTT: Publish, topic: "/Aquarium/Temperature1", length: 31 414279> MQTT: Send type=PUBLISH id=0000 len=31 414394> SLIP: start or end len=0 inpkt=1

From NODE-RED the complete msg is:

Object{ "topic": "/Aquarium/Temperature1", "payload": "26.50", "qos": 0, "retain": false, "_topic": "/Aquarium/Temperature1", "_msgid": "315e531a.2a253c" }

But after about 10'-11':

179407> SLIP: start or end len=60 inpkt=1 179407> cmdParsePacket: cmd=11 argc=5 value=0 179407> cmdExec: Dispatching cmd=MQTT_PUB 179407> MQTT: MQTTCMD_Publish topic=/Aquarium/Temperature1, data_len=1, qos=0, retain=0 179407> MQTT: Publish, topic: "/Aquarium/Temperature1", length: 27 179408> MQTT: Send type=PUBLISH id=0000 len=27 179523> SLIP: start or end len=0 inpkt=1

In NODE-RED now the msg is:

Object{ "topic": "/Aquarium/Temperature1", "payload": { "type": "Buffer", "data": [ 205 ] }, "qos": 0, "retain": false, "_topic": "/Aquarium/Temperature1", "_msgid": "7a5c383c.283c08" }

I see that the payload from a value of "26.50" becomes { "type": "Buffer", "data": [ 205 ] }.

Thanks,

Y.

[ykri]

OK I might have spotted the problem just after I explained it in the previous post. It seems that my SRAM is exhausted because I use this function to convert float values to string before publish them:

char FtoS(float Value) { String vString = String(Value); int length = vString.length() + 1; // +1 allows room for trailing NULL char result = malloc(length * sizeof(char)); // the sizeof here isn't really // necessary for char, but for // portability... vString.toCharArray(result, length); return result; }

Any suggestions of a proper FtoS function?

Thanks,

Y.

[FernandoGarcia]

How about that?

char buffer[5];
String s = dtostrf(floatValue, 2, 5, buffer);

[ykri]

That's it Fernando!!!

Thanks !!!