Read Subscribe message

[PhilC66]

Subject of the issue

command readMQTT() take 5 seconds to give answer if no message,
take 1second if message present

Your workbench

• What platform are you using?
• ESP32
• What version of the device are you using? Is there a firmware version?
• SARA-R510M8S 02.06
• How is the device wired to your platform?
• How is everything being powered?
• Are there any additional details that may help us help you?
• use : SARA-R5_Example17_ThingSpeak_MQTT.ino
  with empty message
  17:18:26.007 -> debut:59236
  17:18:26.007 -> sendCommandWithResponse: Command: +UMQTTC=6,1
  17:18:26.007 -> sendCommandWithResponse: Response:
  17:18:26.007 -> OK
  17:18:31.006 ->
  17:18:31.006 -> readMQTT: sendCommandWithResponse err 4
  17:18:31.006 -> fin:64236

with message
17:18:26.007 -> debut:59236
17:18:26.007 -> sendCommandWithResponse: Command: +UMQTTC=6,1
17:18:26.007 -> sendCommandWithResponse: Response:
17:18:26.007 -> OK
17:18:31.006 ->
17:18:31.006 -> readMQTT: sendCommandWithResponse err 4
17:18:31.006 -> fin:64236

Steps to reproduce

Tell us how to reproduce this issue. Please post stripped down example code demonstrating your issue to a gist.

Expected behaviour

Tell us what should happen

Actual behaviour

Tell us what happens instead

[PaulZC]

Hi @PhilC66 ,

I think this is probably a timeout issue?

First up, it looks like you posted the same serial console messages twice? "with empty message" and "with message" are the same - both show a 5 second delay. But I understand the issue.

In readMQTT, sendCommandWithResponse is called with a timeout of (5 * SARA_R5_STANDARD_RESPONSE_TIMEOUT) i.e. 5 seconds.

So, I think this is expected. If the topic is 'empty', it will take readMQTT 5 seconds to timeout.

Closing. Please reopen if you need more help with this.

Best wishes,
Paul

[PhilC66]

0K, I understand.
How I can avoid polling message instead.
may be using URC?
how to do that?
Thanks for your help
Philippe

[PaulZC]

Hi Philippe,

Looking at the SARA-R5 AT commands manual, the +UUMQTTC:6 URC indicates how many unread messages are in the buffer.

You will need to modify Example17:

Modify the callback processMQTTcommandResult. If command == 6 (SARA_R5_MQTT_COMMAND_READ), result will indicate the number of unread messages. Use this to set a global flag.

Keep calling bufferedPoll in the loop.

Only call readMQTT when the global flag indicates messages are waiting to be read.

I hope this helps,
Paul

[PhilC66]

High Paul,
Very good, I didn't know.
I learned something
Thank you so much
Philippe