[EE] Seeking advice on using NRF24L01 devices

[mike brown]

More game room stuff. I’ve never before used these things, but I’m
planning on having several pairs operating in a smallish area. They mostly
will be used to eliminate wiring between some props. Most will operate in
a single direction and the sender will communicate a very small amount of
information to the receiver, basically telling the receiver to do its thing
and release a magnetic lock or twist a servo motor, one will illuminate an
LED. Really trivial, but imperative that things work.



I’ve been doing some simple tests here and have noticed that these are far
from being 100% reliable; they work, but lost packets are frequent (10% or
so). I’d appreciate any input from folks that have used these in terms of
gotchas or tricks to increase reliability. I’m thinking that if I just
have the sender rocket 50 packets to the receiver, reliability should be
100%.



Are there better methods to accomplish the goal? Would requiring an ACK
response and sending packets until I get one be smarter? It’s imperative
that these things work.



I can’t believe how cheap these are and how nicely the boards are made.
The printed antenna looks like it was actually designed and not just an
afterthought. I remember when these first came along and people had all
kinds of trouble getting them to work. Are they actually refined to the
point of being truly useful. I realize the mess that 2.4GHz is in terms of
interfering devices getting into my way (WiFi, Bluetooth, microwave ovens,
wireless doo dads etc).

[Allen Mulvey]

I am using these for a number of applications. If you use them in Enhanced ShockBurst mode they are very reliable and relatively simple to operate. They repeat the transmission until an ack is received. You can set the number of times it will retry.

Some of what I learned can be found here:
https://forum.mikroe.com/viewtopic.php?f=88&t=59923

I use an RF Explorer spectrum analyzer to set the channel used. In my final iteration I used a dip switch attached to a spare port to manually set the channel on site using a PIC 18F46K22.

For longer ranges I use the unit with the rubber ducky antenna on one or both ends.

One of the nice things about them is that they are all transceivers. I have a pair where one in my garage transmits the status of doors, lights, and temperature. It also controls a relay to switch the outside floodlights. The one inside the house displays the information and has a button to toggle the outside floodlights on or off.

My cheap Chinese versions had only three pipes working but that is not a real problem, as noted in my post linked above, you can designate one data byte to identify your transmitter if you are using more than one. The long pipe address will effectively block foreign transmissions.

Allen

-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of mike brown
Sent: Saturday, October 28, 2017 6:34 PM
To: Microcontroller discussion list - Public.
Subject: [EE] Seeking advice on using NRF24L01 devices

More game room stuff. I’ve never before used these things, but I’m
planning on having several pairs operating in a smallish area. They mostly
will be used to eliminate wiring between some props. Most will operate in
a single direction and the sender will communicate a very small amount of
information to the receiver, basically telling the receiver to do its thing
and release a magnetic lock or twist a servo motor, one will illuminate an
LED. Really trivial, but imperative that things work.



I’ve been doing some simple tests here and have noticed that these are far
from being 100% reliable; they work, but lost packets are frequent (10% or
so). I’d appreciate any input from folks that have used these in terms of
gotchas or tricks to increase reliability. I’m thinking that if I just
have the sender rocket 50 packets to the receiver, reliability should be
100%.



Are there better methods to accomplish the goal? Would requiring an ACK
response and sending packets until I get one be smarter? It’s imperative
that these things work.



I can’t believe how cheap these are and how nicely the boards are made.
The printed antenna looks like it was actually designed and not just an
afterthought. I remember when these first came along and people had all
kinds of trouble getting them to work. Are they actually refined to the
point of being truly useful. I realize the mess that 2.4GHz is in terms of
interfering devices getting into my way (WiFi, Bluetooth, microwave ovens,
wireless doo dads etc).
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[Wouter van Ooijen]

Post by mike brown
I’ve been doing some simple tests here and have noticed that these are far
from being 100% reliable; they work, but lost packets are frequent (10% or
so). I’d appreciate any input from folks that have used these in terms of
gotchas or tricks to increase reliability. I’m thinking that if I just
have the sender rocket 50 packets to the receiver, reliability should be
100%.

These thingies have a mode where they try to get a message trough untill
the other side acknowledges. Did you try that mode?

If possible, try to send state rather than events, and send that state
continously with some random interval. It will get through eventually.

Otherwise you'd have to do some send / repeat-until-acknowleged scheme
yourself.

[Van Horn, David]

The onboard SMPS generates quite a racket, I have seen this make reception nearly impossible.

If you are seeing third harmonic during transmit at or near the data sheet limits, then your antenna network isn't tuned or matched properly.
Tune for resonance then match impedances.

XFdtd is a great way to create PCB antennas that actually work, but it's not cheap.



-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of Wouter van Ooijen
Sent: Sunday, October 29, 2017 7:36 AM
To: ***@mit.edu
Subject: Re: [EE] Seeking advice on using NRF24L01 devices

Post by mike brown
I’ve been doing some simple tests here and have noticed that these are
far from being 100% reliable; they work, but lost packets are frequent
(10% or so). I’d appreciate any input from folks that have used these
in terms of gotchas or tricks to increase reliability. I’m thinking
that if I just have the sender rocket 50 packets to the receiver,
reliability should be 100%.

These thingies have a mode where they try to get a message trough untill the other side acknowledges. Did you try that mode?

If possible, try to send state rather than events, and send that state continously with some random interval. It will get through eventually.

Otherwise you'd have to do some send / repeat-until-acknowleged scheme yourself.

--
Wouter "Objects? No Thanks!" van Ooijen

--
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