Most reliable "best" radio

[NeverDie]

Fun to see what hobbyists can achieve when they stick to it long enough:
https://www.youtube.com/watch?v=SH3lR2GLgT0

[Larson]

@NeverDie Yep, that rocket stuff, and that dedication-to-task stuff, is pretty cool. Thanks for sharing - very inspirational.

At a more modest level ... I received the Atmega 328P programming harness/clamp you recommended long ago. Nice. And your barebones board loaded with my RFM69HCW jig are working nicely. Also received: a bunch of your suggested radios and the carrying boards. Time, I need time. Can't thank you and @alphaHotel enough for the encouragement. I look forward to reporting if only to chronical for my own record and possible use for others.

I hope it doesn't take me 7 years, but it may. Now all I need is a bunch of 48 hour days.

[NeverDie]

What I've learned lately about buzzers, through experimentation, is that to get maximum loudness I need to drive a buzzer within about plus-or-minus 5Hz of its optimum resonance frequency. More than that and the loudness drops off precipitously. Unfortunately, manufacturing variance is probably more than plus-or-minus 5Hz, so that's a potential problem. The voltage supplied on the feedback pin of a piezo is only around 50mv, which is too low for an for an MCU to measure accurately without some kind of extra circuitry to help. It would be nice if the system could self-calibrate the driving frequency to match the inherent resonance frequency of the buzzer.

Meanwhile, I'm switching over to an H-bridge for driving buzzers, because an H-bridge not only efficiently drains the charge that builds up on the piezo buzzer but it also effectively doubles the peak-to-peak voltage seen by the buzzer. At these low voltages, more apparent voltage means more loudness.

When I started this project, I really didn't expect that the buzzer part of it would turn-out to require as much attention as it has! Sure, getting some amount of loudness is not a problem, but really maximizing loudness at these low voltages, while maintaining a tiny footprint and ease-of-assembly, isn't as easy as you'd think a priori.

[Larson]

@NeverDie said in Most reliable "best" radio:

It would be nice if the system could self-calibrate the driving frequency to match the inherent resonance frequency of the buzzer.

Perhaps an initialization User Interface selection? If the big picture is arranged and the region is only 5 Hz, then maybe a centeral default with an user option would be acceptable. Start slow, then rise in 0.25 Hz increments? If the user doesn't repond, then the default is mid-range. As in life, you can only help people so far. I think my mother tried to tell me that once.

Caveat User (Emptor).

[NeverDie]

@Larson said in Most reliable "best" radio:

@NeverDie said in Most reliable "best" radio:

It would be nice if the system could self-calibrate the driving frequency to match the inherent resonance frequency of the buzzer.

Perhaps an initialization User Interface selection? If the big picture is arranged and the region is only 5 Hz, then maybe a centeral default with an user option would be acceptable. Start slow, then rise in 0.25 Hz increments? If the user doesn't repond, then the default is mid-range. As in life, you can only help people so far. I think my mother tried to tell me that once.

Caveat User (Emptor).

You mean make it user selectable?

I'm toying with the idea of an initial calibration using equipment not on the PCB. That's how I arrived at the optimal frequency on my prototype. However, it's unpleasant listening to the frequency sweeps. Even my wife complained about it, and she was in a different room entirely. The only upside is that it's sure to work.

I found a good size for a shell, using a Govee temperature-humidity sensor:

It runs on a CR2477, so it has plenty of depth to it. Nobody seems to shell the shells though, and it would be a shame to canibalize their sensor just for the shell alone. I guess I'll have to 3D print something....

[nagelc]

Check out the Hammond 1551V1gY (vented) or 1151SNAP1GY (unvented).
They look like they are about the same size. I've been using the vented ones for temp/humidity sensors. Not as ugly as most project boxes.

[Larson]

@NeverDie said in Most reliable "best" radio:

The only upside is that it's sure to work.

Very, very funny. Fell off my chair, funny. I had a similar experience with testing buzzers only I failed to recognize the upside/benefit. I ended up putting a switch on the speaker effect to maintain domestic tranquility.

Yes, frequency user selection was my thought. It sounded like the mV range detection/optimization was too complicated. If the design gets close enough to the expected range, then punt to the user for fine tuning.

Shells: Unless a resonant cavity is important, how about a simple tic-tac container with a pre-drilled speaker hole and some hot glue? Maybe a pezz container, if they make those any more? Even a Gatorade bottle cap filled with epoxy might work (use cellophane to cover/embed the mechanical parts of the speaker.) Failure has taught me many things, and this is one of them.

[NeverDie]

Good suggestion on using a tic-tac container. It never would have dawned on me. Too bad I'm on a Keto diet, but I guess I could give the tic-tacs to my son, who doesn't need to diet.

I may have spoke too soon that the nRF52 isn't sensitive enough to read the feedback voltage precisely enough. It turns out to have a 0.6v internal voltage reference, and it has a 12-bit ADC, so in theory it could measure in increments of as little as 0.6v/4096=0.146millivolts. Is that good enough? I really don't know, but I'm going to give it a try. The closer the piezo gets to resonance, the more the feedback voltage should shoot up. I'd be counting on it shooting up by a lot when it hits resonance. So, I just now uploaded the files to a fab for a PCB which can do those measurements, and hopefully I'll receive it in about a week. :-)

[NeverDie]

@nagelc said in Most reliable "best" radio:

Check out the Hammond 1551V1gY (vented) or 1151SNAP1GY (unvented).
They look like they are about the same size. I've been using the vented ones for temp/humidity sensors. Not as ugly as most project boxes.

Good find! I like the vented ones, as it look like they would let out a lot of sound.

[NeverDie]

@nagelc said in Most reliable "best" radio:

Check out the Hammond 1551V1gY (vented) or 1151SNAP1GY (unvented).
They look like they are about the same size. I've been using the vented ones for temp/humidity sensors. Not as ugly as most project boxes.

@nagelc I ordered the white version of the vented model you referred to so that I can give it an up-close looky-loo. I also found an interesting "similar but different" vented enclosure from New Age Enclosures, though at twice the price, which I also ordered for comparison:

https://www.mouser.com/ProductDetail/789-P1A-151510
With benefit of hindsight, maybe I should have started to look at possible enclosures from the get-go, because, depending on what's available, that may very well determine what form factors are even worth considering. :face_palm: i.e. the project will end-up needing to fit the enclosure, probably not the other way around.

[NeverDie]

I think I may now finally understand the purpose of the optional S0, LENGTH, and S1 fields in the nRF52 packet frame. The datasheet gives very little insight into them, so I had previously disabled those fields just to avoid the topic altogether because it seemed so obscure. However, in trying to figure out how to send/receive packets between an nRF52 and an old-style nRF24L01+, the puzzle finally makes sense: they are there to either 1. provide a means of compatability with the nRF24L01's Enhanced Shockburst, which puts a 9-bit field in the middle of the frame:

or 2. allows you to roll-your-own super Enhanced Shockburst with extra bits (in which case standard nRF24L01P ESB compatibility goes out the window). Well, for a host of reasons, I think nRF24L01p compatability is worth enduring an extra 9 bits of airtime, so I'll go that route and configure the nRF52 accordingly now that I've inferred what those fields are meant for. :face_with_cowboy_hat:

[kirianjahiem]

I like your ideas. Is there a circuit for common mode rejection? It would be worth exploring. And using a test port for different pull-up resistors, better yet a variable resistor, would allow for testing.

[NeverDie]

Reporting back on the E01-2G4M27D radio's that I had referenced earlier. For those who don't remember, these are nRF24L01P radios that have been upgraded to use a 27dBa PA and, allegedly, other higher quality components (https://www.ebyte.com/en/product-view-news.aspx?id=450). 27dBa = 0.5 watt. For comparison, the maximum Tx power of a plain nRF24L01 is just 0dB. I had occasion to try them out today, and they appear to perform extremely well, even at 2mbps while transmitting over the worst-case transmission path in my house that I've been using to test all the radios on.

I'd venture to say that in terms of reliably getting a packet through to its destination, they outperform all other enhanced nRF24L01P's that I've ever tried previously. If you opt to try them on the test platform, as I have done, I recommend you upgrade your BoB capacitor to 100uF or 200uF, because 10uF doesn't seem to be enough when transmitting from somewhat weak batteries. Nonetheless , 10uF is sufficient if powering it from a really stiff power source. Ironically, they vastly outperform the 2.4Ghz LoRa radios that got me started on this whole mini-blog in the first place.

Looks as though you can buy them on sale at $4.59 each: https://www.aliexpress.com/item/2255800350626109.html?gatewayAdapt=4itemAdapt
No, they don't come with the antennas. You'll have to source those separately.

I'd say the main downside to these modules is that there does not appear to be any way to dial-down the transmission power, so that you only use as much power as you really need to fit your circumstances. There's no reason that such a module couldn't be designed and built (just as the RFM69HW allows), but, AFAIK, there aren't any on the market like that for the nRF24L01P. It's such an obvious enhancement that I'm surprised none of the vendors have offered it, even if it requires extra pins. Maybe someone reading this knows of one? If so, please post.

[NeverDie]

:face_palm: Doh! It just occured to me that rather than being a fixed output power, maybe these modules actually do have adjustable gain via adjusting the power output of the nRF24L01P:

That would perhaps mean that you could adjust the power output to be 27dB minus 18dB = 9dB? i.e. they effectively offer a gain of 27dB to whatever output power your radio chip already has? Is that how PA's work? Or, instead, would it just be blasting out mostly noise at 27dB if I were to set the nRF24L01P's output power to -18dBm? I'm guessing the former and not the latter, but unfortunately I don't have any radiated RF power measuring equipment that might tell me the answer. Anyone know? Perhaps measuring the current consumed during transmission would tell the tale, as one could infer the output power from that. Hmmmm...... Worth a try. Might be able to approximate the answer from that. If it turns out that they are adjustable in this manner, then I would think they are pretty awesome as a default "go to" module for just about anything. i.e. you'd have good communication even on the low-end of 9dB, but you would also have plenty of headroom to notch it up to a higher output power if it were truly necessary to cover whatever contingency you might run into, provided it remains within the legal limits of whatever your jurisdiction is.

I once tried (and reported on) a 4watt 2.4Ghz amplifier that you can buy on amazon, and it had a "sweet spot" for input power that it could amplify from, but below that sweet spot it didn't do much good at all. Perhaps that's a more accurate model of how this works in real life?

Looking at the manual, it does say the output power is multi-level software adjustable, so there's hope. https://www.ebyte.com/en/downpdf.aspx?id=450 I don't see that it offers any hints beyond that though.

[NeverDie]

Well, attempting to answer my own question above, here is the power profile of the E01-SG4M27D when the nRF24L01P is set to 0db (plus whatever power the PA on module boosts that to):

Here it is when the nRF24L01P is set to -18dBm ( (plus whatever power the PA on module boosts that to):

So, it looks as though the latter is the current is roughly 1/3 of the former, and since the voltage is the same, that would imply that the power is about 1/3 also. However, if my earlier theory was right, then the second chart should be showing a maximum of about 7.4mw, as compared to the theoretical 500mw of the first chart.

So, really, neither chart makes much sense. 3.3v x 580ma = 1.9 watts and 3.3v x 180ma = 0.594 watts. Well, I guess that's wrong if the radio module converts the 3.3v to a lower voltage for running the radio at via an LDO, which means it disappates the difference as heat. Still, the ratio between high and low Tx power is something like 3 to 1, whereas in theory it should be more like 67 to 1. So, I really don't know what to make of all that, other than the PA doesn't have much dynamic range to it. Does that extra power at the low end translate into proportioinately more radiated RF? I have no way of knowing, as this is the limit of what I can test with the equipmet that I have. I'd need something which can measure actual radiated RF.

This guy demonstrates how that might be done:
https://www.youtube.com/watch?v=FVaiWzJSvNU

In a nutshell, it would require both the power meter and, in this intance, an attenuator to go along with it.

I suppose an alternate, non-elegant way to solve the problem would be to have an array of different nRF24L01 modules, each optimized for a different power level. Then, by selecting the right CE pin, you could switch among them for the desired power level for a transmission. Not completely outlandish if size doesn't matter so much, because nRF24L01P modules, in whatever flavor, are generally fairly cheap--perhaps cheaper than buying the $80+ worth equipment needed to measure RF power that would probably be only one-time use. So, for a gateway, that might be a possibility. For a sensor node, probably not.

[NeverDie]

@NeverDie said in Most reliable "best" radio:

I think I may now finally understand the purpose of the optional S0, LENGTH, and S1 fields in the nRF52 packet frame. The datasheet gives very little insight into them, so I had previously disabled those fields just to avoid the topic altogether because it seemed so obscure. However, in trying to figure out how to send/receive packets between an nRF52 and an old-style nRF24L01+, the puzzle finally makes sense: they are there to either 1. provide a means of compatability with the nRF24L01's Enhanced Shockburst, which puts a 9-bit field in the middle of the frame:

or 2. allows you to roll-your-own super Enhanced Shockburst with extra bits (in which case standard nRF24L01P ESB compatibility goes out the window). Well, for a host of reasons, I think nRF24L01p compatability is worth enduring an extra 9 bits of airtime, so I'll go that route and configure the nRF52 accordingly now that I've inferred what those fields are meant for. :face_with_cowboy_hat:

It worked! :smile: :smiley: :slightly_smiling_face: Well, sort-of. I have it working using the five byte address 0xE7E7E7E7E7, which dodges the question of how the address bytes are ordered over the air in one scheme versus the other. That's the next puzzle to solve. You might think this would be easy to solve, as I did, but so far not.

Here's part of what's weird (this is taken from the nRF52 datasheet):

Can you see the disconnect? On the nRF52 the LENGTH field comes in the middle of the 9 bits, whereas on the nRF24L01 ESB it comes at the front of the 9 bits.

Also, I haven't been able to get any non-repeating address to work yet. e.g. x0101010101 works, and so does 0xE7E7E7E7E7, but that's a rather limiting type of address to rely upon, though I suppose I could live with it if I had to. Go figure.

[Larson]

@NeverDie You are building a library. I don’t have the time to consume/enjoy it now as I’m deep in eldercare. But for sure, I’m coming back to your wonderful library to learn more – just later. Don’t interpret my silence as… indifference.

[NeverDie]

@Larson No worries. It works better with feedback from a knowledgeable audience, but... that entire audience has seemingly evaporated. Nonetheless, this rubber ducking may still have some value even under the current "everyone long gone" circumstances.

[NeverDie]

Aha! Apparently there is some kind of undocumented difference in the way addresses are represented in an nRF24L01P vs. an nRF5x. I found this address conversion function in Nordic's "micro-esb" library (https://github.com/NordicPlayground/nrf51-micro-esb/blob/master/common/micro_esb.c ) which holds promise for illuminating what that difference is:

and

Just from eyeballing it, nRF24L01P apparently transmits in the order of most significant bits first (which is undocumeneted), as compared to nRF5x, which transmits in order of least significant bits first (which is documented). Well, that would explain why xE7 (=B11100111), worked in my earlier addressing attempt, since it is the same either way.

Well, yes, though the algorithm is a two-step process. The bytewise_bit_swap function apparently reverses the ordering of bits in each byte, but leaves the bytes in the same order:

1111111111111111111111110100 -> 11110000111111111111111100101111
1111111111111111111111110011 -> 11110000111111111111111111001111
1111111111111111111111110010 -> 11110000111111111111111101001111
1111111111111111111111110001 -> 11110000111111111111111110001111
1111111111111111111111110000 -> 11110000111111111111111100001111

The radio address config section then reorders the sequence of the bytes. The net effect is the same as what I had guessed.
Well, this does explain why on the nRF5x, the "prefix" comes after the address section in the above diagram. My original impression had been that it was a poor choice of nomenclature.

Next I need to test this new theory on the hardware and see if it works.

[Larson]

@NeverDie said in Most reliable "best" radio:

I suppose an alternate, non-elegant way to solve the problem would be to have an array of different nRF24L01 modules, each optimized for a different power level.

Does the optimization mean different HW components with different RF_PWR settings? If the HW remains the same then one could incrementally change the RF_PWR level in the loop, right? Perhaps even by using two input pins one could control the RF_PWR level settings manually. The pins determine 00, 01, 10, or 11 and that gets fed to RF_PWR. That might be easier.