Alex's Corner - Week 4 - WiPy & Publishing/Subscribing With MQTT

[PiAir]

@bucknall You know I watch them :) but it is during work hours, so joining in live is going to be a bit difficult. They don't mind me playing with the LoPy in the evening or in the weekend, but during the day I'm supposed to do other stuff.
I can totally understand you don't want to try another TTN live demo. :)

[bucknall]

@PiAir Not worried about trying another demo - I might try to set up the gateway with another network such as Loriot in the future or at least try again once TTN is working correctly.

I've pushed the docs updates regarding the LoRaWAN TTN Nano-Gateway code to our docs now so that should be going live next docs update. I'll post an update when it's online.

[robmarkcole]

@bucknall Since I can't attend the demo live, my questions are:

1. How to handle authentification - user and password? Also can I keep passwords separate from the main code? Are passwords encrypted over the network?
2. Bandwidth - what is max rate I can push readings over MQTT?
3. Sleep mode - if I wake from sleep mode are messages that were sent whilst sleeping received?
4. The docs mention a bug on line 57, I guess you will cover addressing that https://docs.pycom.io/pycom_esp32/pycom_esp32/tutorial/includes/mqtt.html
5. One final question, is it possible to pass a variable into a running python program using MQTT? For instance, could I pass in (via MQTT) the variable which sets how frequently the Wipy takes a measurement?

Cheers!
p.s. if you do a demo, perhaps also use a local MQTT broker on your mac, with mosquitto? Seems the most generic approach to me rather than a cloud service..
p.p.s. for week 5 perhaps you could cover/mention the json library? :-)

[bucknall]

Links that I mentioned in my the live stream:

• http://www.bitreactive.com/how-fast-can-you-publish-mqtt-messages/
• http://www.hivemq.com/blog/mqtt-essentials-part-4-mqtt-publish-subscribe-unsubscribe
• https://simplifiedthinking.co.uk/2015/10/03/install-mqtt-server/

[robmarkcole]

Perfect! Is the video available to download?

[bucknall]

@robmarkcole it's hosted on YouTube so you can view it back whenever you wish. Regarding downloading it, I'm sure you can but I won't advise tools to do that as I believe it's against YouTube's Ts & Cs...!

[robmarkcole]

@bucknall MQTT up and running now, thanks!

[robmarkcole]

Hmm this working before lunch, what could be going on?

[bucknall]

@robmarkcole I have a lot of problems using hivemq, its often down - maybe try another broker? like mosquitto?

[robmarkcole]

OK great, now publishing temperature readings from my DS18B20 to my Mac via MQTT. However I note that client.connect() returns 0 even though the connection is working..

[RL-Auroraim]

Hi @bucknall

I would like to have our LoPys interpret incoming subscription messages and execute a corresponding function. How do I go about saving subscribed messages as a string variable for example so I can compare them?

[PiAir]

@RL-Auroraim You can see an example of subscribe here in the video: https://youtu.be/3NDPSbr5J14?t=12m57s that Alex posted. But it looks like he hasn't pushed that one to github yet? (correct @bucknall ?)

[bucknall]

@PiAir That's correct, I'll make sure that's updated on both the docs & GitHub! Cheers!

[RobTuDelft]

Link in Youtube description seems to link to the week 5 forum topic

[robmarkcole]

@bucknall just posted about sending images over MQTT, perhaps one for another Corner?

[audreycrist]

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[ngthanh]

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