tomsimmons
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Wireless Comms Options

Mon Apr 05, 2021 8:19 pm

I have a Pico that is connected to a weather station (vane, anemometer, rain gauge) and a BME280 (temperature, humidity and pressure). I'll likely expand the range of sensors as time progresses.

What I'm seeking input on is the best option for wireless comms from the Pico to a Pi in the house to receive either near continuous or burst updates from the Pico. Burst would still be pretty frequent.

Wifi is out as it is right on the limit of the range from the router.
Bluetooth - too far.
433/866 MHz - definite option, nice and cheap too
2.4 GHz - haven't looked into this yet
LoRaWan - interesting
Polystyrene cups and string - baud rate too low and poor noise handling in wind...
Other suggestions?

I'm coding in MicroPython, from what I have read the pyrf (think that is the correct library) that is used for 433/866 on a normal Pi doesn't exist, so I'd need to implement my own parallel to serial transmission routine on the Pico end - not that difficult from what I understand.

Lower power is important as ultimately I aim to power everything from a solar panel charging a LiPo or similar cell. The range isn't that far, but there are a couple of brick/stone walls to pass through.

Bandwidth at the moment doesn't need to be high, but I might consider adding cameras to the station which would change that.


Tom

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nick.mccloud
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Re: Wireless Comms Options

Tue Apr 06, 2021 5:54 pm

Mostly guesses as you don't mention how far away your weather station is?
tomsimmons wrote:
Mon Apr 05, 2021 8:19 pm
2.4 GHz - haven't looked into this yet
LoRaWan - interesting
Polystyrene cups and string - baud rate too low and poor noise handling in wind...
Other suggestions?
NRF24L01 for your 2.4GHz option
LoRaWAN via an AT modem module - easy enough - but then you need a gateway unless someone else has one near by - will never do pictures
Polystyrene cups - I find the acrylic picnic wine glasses work well with mono-filament fishing wire
Other: IP over Avian or small child relay or morse code flashing light

WiFi directional antenna - look like mini radar dishes - cheap & work well and can do pictures too. Turn the ESP-01 on & off as required. Find them on eBay
Pico/RP2040 ≠ Arduino
Pico = hot rod kit car, Arduino = hot rod kit car wrapped in cotton wool with buoyancy aids & parachute

tomsimmons
Posts: 139
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Re: Wireless Comms Options

Tue Apr 06, 2021 7:49 pm

@nick.mccloud

Thanks for the reply.

I was surprised the WiFi was so poor as the distance isn't that great, 30-40 m at a guess, but thinking about it I think the alignment of the 3' thick stone walls, then brick walls after that couldn't be worse. The straight line between the router and Pi already out there probably runs pretty much through the length of the wall!

IP over Avian, too many native distractions for the carrier medium.

Small Child Relay - these days they are too unreliable and expect payment!

Morse by light, interesting, how do you handle it in bright sunny days particularly with a north south alignment - not a common problem I grant you in North East Scotland, but records to indicate it could happen.

LoRaWAN, I have pretty much ruled out as there is no existing network available, so without setting all that up too, there seems little benefit over 433, in fact, more negatives.

So it looks like I'm, left with 433, 868 or 2.4. There doesn't seem a lot to choose in price between the modules. How you interact with the modules would seem to be identical. 2.4 seems to have the higher data rate - is that correct?

Am I correct that I would need to "bit bang" the feed to signal connection as the py-rf lib doesn't exist in MicroPython?


Tom

EvanEscent
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Re: Wireless Comms Options

Tue Apr 06, 2021 8:21 pm

As nick says the NRF24L01(+) - the data rate can be 2Mb I think.

I recall there's a 900MHz module that gives ranges in miles but
it's costly. https://www.digi.com/products/embedded- ... -pro-900hp
I read, I tinker, I test, I repeat.
Sometimes I learn.

tomsimmons
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Re: Wireless Comms Options

Tue Apr 06, 2021 8:52 pm

Are you able to recommend specific 2.4 hardware?

I was looking for info on them and saw a lot of bad reviews of poor quality modules that don't work, or only manage a very short range.

Tom

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HermannSW
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Re: Wireless Comms Options

Tue Apr 06, 2021 9:14 pm

There is a proprietary ESP32 1km Wifi mode with free line of sight:
https://www.cnx-software.com/2021/03/25 ... ter-range/

Connect one ESP32 serially to Pico, and use the other connected to whatever.

1km free line of sight should be able to do 40m with stone walls, but testing is needed to confirm.
https://github.com/Hermann-SW/memrun
https://stamm-wilbrandt.de/2wheel_balancing_robot
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://stamm-wilbrandt.de/en/Raspberry_camera.html

EvanEscent
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Re: Wireless Comms Options

Tue Apr 06, 2021 9:27 pm

"able to recommend"

At the limits of my knowledge but stone walls aren't 2.4GHz friendly.
I'm guessing you'd have to up the power a lot even to get a weak signal.
5GHz can be blocked by drywall, it seems. So lower frequency seemed
to be your best option.
I read, I tinker, I test, I repeat.
Sometimes I learn.

lars_the_bear
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Re: Wireless Comms Options

Wed Apr 07, 2021 7:48 am

You need a wire, and a long drill bit ;)

Seriously, even if you don't want to/aren't allowed to drill the walls, is there not some other cable route you could use? Are there water/electricity/gas/drainage chases you could follow?

With lowish signalling rates even a simple screened cable should give you 100m or so. RS-422 and screened twisted pair should be good for a kilometre.

I understand the appeal of wireless operation, but I think we've become too dependent on it, and reluctant to consider anything else.

Kevin.

tomsimmons
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Re: Wireless Comms Options

Wed Apr 07, 2021 9:08 am

EvanEscent wrote:
Tue Apr 06, 2021 9:27 pm
"able to recommend"

At the limits of my knowledge but stone walls aren't 2.4GHz friendly.
I'm guessing you'd have to up the power a lot even to get a weak signal.
5GHz can be blocked by drywall, it seems. So lower frequency seemed
to be your best option.
I was thinking this, as WiFi is 2.4 GHz.

lars_the_bear - I considered this, where it currently is there is a cable, the final location however will be up a chimney, and the only cable available then would be a TV aerial - so not really an option.


Tom

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bensimmo
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Re: Wireless Comms Options

Wed Apr 07, 2021 9:50 am

Lora/lorawan/433/868/916 are all basically the same just a different implementation, but see what your micropython can handle.


How I would do it.

Or
Dump the Pico and buy an ESP32.
See if WiFi just reaches, if not buy a better WiFi setup (mesh for £100ish three units), it'll be good for the house use anyway and nice for camera use.

You can still use micropython with ESPs

Have the ESP deep sleep when not in use, don't send data as frequently.

Lora/lorawan receiver/gateways are reasonably easy to setup on a Pi, just grab the RFM96 chip for your region and wire it up directly.
Run some software, Adafruit circuitpython works quite well.
You don't need the LoraWAN Gateway part though.

Again you could just buy an ESP with a Lora chip already. TTGO, they also have the charging and batteries setups ready.

lars_the_bear
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Re: Wireless Comms Options

Wed Apr 07, 2021 2:08 pm

tomsimmons wrote:
Wed Apr 07, 2021 9:08 am
lars_the_bear - I considered this, where it currently is there is a cable, the final location however will be up a chimney, and the only cable available then would be a TV aerial - so not really an option.
Yeah. Sounds like a pain.

But... I've learned from bitter experience that a solar charger in an inaccessible place is unlikely to be maintenance-free. The batteries don't last forever, and the cells get covered with wet leaves, birds*hit and general smeg. If you could somehow get a cable up there, you could use it for power as well.

FWIW I've got electronic equipment mounted on a 10m carp fishing rod attached to the side of my house. It's taller than the chimney, but I can easily (well, easy-ish-ly) bring it all down for maintenance. The cabling, and the equipment, get hoisted up the pole using a pulley, like a ship's halyard. Of course, I doubt you'd get away with this in a conservation area. And it does tend to lean a bit in strong winds.

My point is that, perhaps, when all the obvious approaches seem to be unsatisfactory, perhaps it's time to consider a different approach entirely?

Kevin.

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bensimmo
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Re: Wireless Comms Options

Wed Apr 07, 2021 5:11 pm

Given its going on a chimney, with a cable route. Then run some Ethernet cable up along that same route when you out it up there, power via PoE injection... And use a slow Ethernet for a reliable connection.?

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