Most reliable "best" radio

[NeverDie]

@Larson What good luck: looks as though the pinout is an exact match for the pinout on my nRF24L01 adapter board for the test platform:

Makes me wonder what those two through-holes are for near the antenna?

Looks as though they are meant for something. Anybody know what those two through-holes are for?

[NeverDie]

Ignoring the warning about not transmitting for longer than 4ms at a time, I'm presently trying to blast out a continuous stream of packets from the nRF24L01 at 2mbps datarate without pausing between packets. According to the datasheet, one way to do it would be to start sending the first packet while ensuring that the Tx FIFO never empties. However, none of the libraries seem configured for doing that, so it involves working with the nRF24L01 at a lower level. In the worst case, I guess I could settle for a 4ms long packet train if that's the best it can do, but maybe an nRF24L01 equipped with a TCXO could perhaps go longer than 4ms? The 4ms is evidently a PLL limitation, and I'm not sure exactly how the PLL interacts with the crystal, or whether or not a better crystal will lengthen the continuous transmit time.

Anyone here tried this before? I mean, come on, a lot of people here use the nRF24L01 as their go-to transceiver. Anyone? Anyone? Bueller? Anyone?

[skywatch]

@NeverDie It has an on-board frequency synthesiser so maybe during tx the temp rises on the substrate and this affects tx frequency stability? So it could be the FS rather than the PLL. Again just guessing here....

[NeverDie]

I went and did it. I got it to transmit continuously for many seconds before it peters out. And the packets it sends can be received, decoded, and understood. Exactly how long it goes seems to vary from one burst to the next, but a reset gets it going again. Anyhow, it works more than long enough for my purposes. :smile:

In case you're wondering why the current draw isn't higher (as it was in earlier pictures), it's because I turned the power all the way down to minimum, since I'm testing at close range.

[NeverDie]

Also, I'm happy to confirm that the amazon smd nRF24L01 modules that I ordered (see earlier post) have a pinout that matches my nRF24L01 adapters. I've tried it out, and it works:

That said, what I received is a little bit different than what was pictured in the amazon listing. If you look at the through-holes that are near the antenna, one of them is much smaller on the modules that I received. It's much more like a via than a through-hole.

[NeverDie]

Lastly, it sounds as though the shortage of legacy chips is going to continue for quite some time:
Where The Real Chip Shortage Is – 11:53
— Asianometry

The TL;DR is that there's little profit in those chips, and so there's no motivation for manufacturers to build expensive new plants to pump out yesterday's technology. I posted recently about the attiny3226, and now I wish I had bought some, because they're now all out of stock everywhere. I'm therefore debating whether to buy some attiny3224's, which lack as many pins, because they're presently in stock but soon will be sold out, jut like the attiny3226's. It might be years before things get back to normal.

[Larson]

@NeverDie said in Most reliable "best" radio:

Makes me wonder what those two through-holes are for near the antenna?

On ESP8266's, I wondered if the PCB antenna could be cut with a dremel tool and be fitted with an equivalent whip-wire. It would be cheap enough to try. It looks to be that the NRF24's are maybe making that easier? Again, cheap enough to try.

Thanks for all the updates to https://www.openhardware.io/user/310/projects/NeverDie#view=projects I've been busy updating all the files I've collected. You have been hard at work. All the added *.png and *jpg pictures really help. The *.rar files make it really easy to get into the guts of it all. I got KiCAD downloaded and am looking at the E28 project at the moment. Learning a new CAD tool will be a climb of its own for me.

For the benefit of others: To extract the *.rar in Windows 10, I downloaded a utility program (WinZip 21-day trial). Maybe everyone already knows that. What I have learned is that getting to the KiCAD files is a three step zip-sandwich procedure:

1. download and unzip the openhardware *.zip file.
2. find the *.rar file and use a utility like WinZip to unwrap it.
3. unzip the resulting *.zip file.

The resulting four files (*.pcb, *.prl, *.pro, and *.sch) will deliver KiCAD access as a project via the *.pro file. It took me most of the day to learn that. There is probably an easier way.

[NeverDie]

@Larson said in Most reliable "best" radio:

unzip the resulting *.zip file.

Uh, oh. As Bug's Bunnny would say, you may have made a wrong turn at Albuquerque, or, in this case, on step 3.

There is, I think, a much simpler way. Instead of manually unzipping the .zip file and trying to make sense of the contents, do this instead: in Kicad 6, under the "File..." menu, go to "Unarchive project...." and give it the intact .zip file. It will instantly recreate the entire project on the spot, exactly where I left off with it. It really couldn't be simpler. Try it. You'll like it.

Regardless, thanks for the feedback. I just now changed the instructions on the openhardware.io projects to make it more clear what to do.

[NeverDie]

@Larson said in Most reliable "best" radio:

I wondered if the PCB antenna could be cut with a dremel tool and be fitted with an equivalent whip-wire. It would be cheap enough to try. It looks to be that the NRF24's are maybe making that easier? Again, cheap enough to try.

No need to guess. It's been done already. Here's one of the mods:
Cheap DIY NRF24L01 Antenna Modification – 02:48
— Pete B

This one looks even better: https://www.instructables.com/Enhanced-NRF24L01/

I haven't tried either one, but I do believe them when they say it helps improve range a lot.

[NeverDie]

@Larson said in Most reliable "best" radio:

You have been hard at work.

Yup, and although it's jumping the gun, I think I'm ready to reach conclusions. For battery powered nodes, I think for short-range the answer is si24R1, because it offers 2mbps and 7dBm and you can buy tiny, compact modules with in-built PCB antennas for around 50 cents each, as you have already done. Also, mysensors offers over-the-air updates with nRF24L01/si24R1, which is compelling. So, if you have a gateway within range, I see no problem with those radios. For longer range, I think the answer is SX1262 because FCC allegedly allows higher transmit power with spread spectrum, and it has a very large potential link budget. If powered by mains, I'd say ESP8266, which is what I will use to gateway the si24R1 and SX1262 motes. I could test and compare more radios, but I don't have infinite time, so I think that's as far as I'm going to take it for now. If anyone else wants to try more stuff and report back and/or make comparisons, I'd say by all means go for it. For instance, anything that does genuine frequency hopping would be worth looking into. Frequency Hopping would maybe get the best of both worlds, with a combination of high speed, a large link budget, and interference avoidance. This guy does a comparison of LoRa vs Frequency Hopping, and you can see why Frequency Hopping Spread Spectrum seems more compelling than LoRa:

LoRa Vs Spread Spectrum FHSS 2.4 GHz – 10:13
— 0033mer

What's interesting is that the FHSS module he demos actually uses the nRF24L01 chip inside it to accomplish the FHSS! See https://www.ebyte.com/en/new-view-info.html?id=450 So, I take that to mean that with the right software, one could program an MCU to get the nRF24L01 to do FHSS. I do wonder though just how it manages to do it. AFAIK, true FHSS requires psuedo-random changes in frequency while transmitting a single packet, not sending short packets in a pseudo-random sequence of different frequencies. Hmmm.... Maybe it just strips off all the header bytes, and does it that way? Maybe then there would be no difference. I'm guessing maybe that's how they do it. You could compute your own CRC and send the CRC bytes as part of the payload instead of in a separate part of the frame. In fact, that might even be better, because then you could do CRC32, whereas the nRF24L01 hardware encoding seems limited to CRC16. You send what would have been frame bytes as purely payload bytes, creating a kind of virtual Frame. Also, by chopping up the transmission--you could effectively send payloads that are longer than 32 bytes, which is the limit for any single packet on the nRF24L01--by loading and sending more than one pipe's worth of data. This is notionally similar to how I was able to get the nRF24L01 to transmit continuously (see earlier post) without dropping into standby/idle between packets.

[Larson]

@NeverDie said in Most reliable "best" radio:

No need to guess. It's been done already. Here's one of the mods:

Very interesting. Based on the measurements the author, Pete B, shows, the on-board antenna length is 33.3% the 1/4 Lambda WL. He adds 66.7% for a total 1/4 Lambda. I'll say the same thing is probably true for the ESP8266 antennae lengths. I'm looking forward to trying this with the ESP.

[Edit: My mistake. I looked at this further. The full 2.4GH WL is 4.92". So, the onboard measured 1.64" WL is a 1/3 WL. The additional 3.28" would bring the total WL to 1.0 * WL. Several simple RSSI tests would show the results. Frist test would be no change for a base case. Then test with the addition. Then one could cut the wire back to 3/4 WL, 1/2 WL, 1/4 WL, then finally remove the antenna to verify the original test, or to inspect for circuit damage.]

[Larson]

@NeverDie said in Most reliable "best" radio:

conclusions

Yes, I feared that I would be too late to the game to help. I hope to report back with some results after the boat from China arrives. I'd like to do the 2-D map of RSSI values with different radios.

[Larson]

@NeverDie said in Most reliable "best" radio:

Try it. You'll like it.

I tried about 5 times. I'm able to get to the project files but not through KiCAD (6.0.05) using File/UnarchiveProject so ultimately, I've succeeded. File/UnarchiveProject takes the *.zip file just fine, but it does not deliver the *.pcb, *.prl, *.pro, and *.sch files. File/UnarchiveProject does deliver the *.rar file along with the "design" and "image" directories. File/UnarchiveProject won't take a *.rar file. So ultimately, I use the zip utility to get it. The important part is that I can see the files in KiCAD.

Reporting from the slow road, Larson.

[NeverDie]

@Larson said in Most reliable "best" radio:

@NeverDie said in Most reliable "best" radio:

conclusions

Yes, I feared that I would be too late to the game to help. I hope to report back with some results after the boat from China arrives. I'd like to do the 2-D map of RSSI values with different radios.

Sounds good. The game isn't going anywhere. It'll still be here whenever you're ready. It never ends, and it will outlive both of us.

[skywatch]

@NeverDie That 'antenna modification' just looks crazy to me, but I have not tried it. However the designers will have spent some time on getting the pcb stripline antenna to be matched to the transmitters impedance. Adding a random bit of wire on the end will screw this up royally.. You never see this on TV antennas or anywhere else for that matter (maybe some nutter with a car aerial made from a coat hanger).

Also I would expect that the design is to be as wide band as possible but centered on the mid frequency in the range available. So the further you move away from 'centre' frequency (Ch63) then the worse the antenna is likely to perform. But at the power levels used here the effects might be marginal. I have always found moving the RF board a cm or two can make a big difference in link quality.

Here is the link to the E32 arduino library..... https://www.arduino.cc/reference/en/libraries/ebyte-lora-e32-library/

[NeverDie]

Regarding the antenna extensions, you raise some good points. The people who posted them seem like they thought it genuinely helped, but maybe I was gullible and was wrong to post the links. If so, I'm sorry. On the other hand, it might take only 5 minutes to try them out and see whether or not they work. A simple trial experiment would maybe settle it one way or the other pretty quickly.

@skywatch said in Most reliable "best" radio:

Here is the link to the E32 arduino library..... https://www.arduino.cc/reference/en/libraries/ebyte-lora-e32-library/

Thanks. What was it you were wanting me to notice about the e32 library? If it was about the FHSS, that was an e34 module in the youtube video.

[skywatch]

@NeverDie said in Most reliable "best" radio:

Regarding the antenna extensions, you raise some good points. The people who posted them seem like they thought it genuinely helped, but maybe I was gullible and was wrong to post the links. If so, I'm sorry.

We are all here to share and learn and help each other out - I was only adding my thoughts on the matter for all to consider.

On the other hand, it might take only 5 minutes to try them out and see whether or not they work. A simple trial experiment would maybe settle it one way or the other pretty quickly.

Yes it would, but positioning needs to be carefully maintained to avoid false results.

@skywatch said in Most reliable "best" radio:
Thanks. What was it you were wanting me to notice about the e32 library? If it was about the FHSS, that was an e34 module in the youtube video.

Oh darn it! - I got it mixed up - I am sorry for posting the wrong lib!

[NeverDie]

@skywatch said in Most reliable "best" radio:

Yes it would, but positioning needs to be carefully maintained to avoid false results.

I think for a gateway it could make sense to use two nRF24L01 modules spaced a half wavelength apart. Then for reception you'd get all the benefits of antenna diversity, and for transmission to a particular node you could simply pick the module that receives the most packets out of the two from that node, which should give the better signal path. That could cut down on the sensitivity to positioning by better avoiding null zones.

[Larson]

@skywatch said in Most reliable "best" radio:

That 'antenna modification' just looks crazy to me,

And that is why it will be fun to test. I corrected my post above and made comments on testing.

[Edit: It was my bad for drawing people down this dark alley of antenna modifications. I’ve learned much from dark allies and only been beaten-up a few times. Yet, I still go there… to learn. Therefore, I will test it and reply.]

[NeverDie]

I just now did a current measurement, and, unfortunately, the allegedly smd NRF24L01's on amazon do not appear to be either nRF24L01's nor si24R1's, because the max Tx current is not a match for either:

The Tx current is too high to be an nRF24L01, and it's too low to be an si24R1. I'll have to look at some of the alternative datasheets to determine just what it is.