Frequency hopping experiments on the NRF24

[Martin]

Yes, if you know you have a good ESC with a reliable 5V BEC output, then it's best to power the RF-Nano from that, into the RF-Nano's VCC (5V) pin.

The only reason I suggest possibly using the Vin (or Raw) input is if you have a 5.5V or 6V BEC, or I've seen some switch-mode BECs that have very noisy 5V output - especially when the motor is running about half-throttle. In these cases it might be better to feed the RF-Nano into its Vin (Raw) input from the main flight power pack: direct for a 2-cell pack, or via a dropper diode (or LED) for a 3-cell pack.

It does complicate the wiring though, so if you have a good reliable 5V BEC, keep things simple and power all the radio gear from that, as Phil suggests.

It's important NOT to power the RF-Nano from 5V into its Vin (Raw) pin: although it would most likely work, the on-board regulator drops about a volt, so the RF-Nano, including its nRF24L01 would then be running at only 4V. The chips would probably work okay at this, but it's outside the spec of the main Atmel chip to run at 16MHz from only 4V, so it wouldn't be as reliable.

[MaxZ]

I'm powering mine via Vcc as an input with 5v (actually a Li cell, but could be a BEC)

Phil, what kind of cell would that be? As far as I know the voltages range from 3.2v (LiFePO4) to 3.8V - 3.85V.
They all seem a bit low to run a decent servo from, also the Nano RF needs 5V Vcc, no?

I still have not bitten the bullet, but I am thinking of trying it out on the two small sailing dingy's ("Footy" class) that I built.

The other stuff on how to connect them up is clear to me now.

Cheers,
Max.

[MaxZ]

Right, I did bite the bullet and ordered the boards, both high power and low power versions. So more questions if I may....

- I intend to start experimenting with the low power, integrated Nano+NRF24L01+ version, both as Rx and Tx.
I have a couple of Taranis stick units lying around, so I will design a casing around those. Q: is there a preferred orientation of the pcb antennae? My gut feeling says parallel planes, Cu side facing between Rx and Tx....

- Is there anything against using the full FHSS sketch rather than sticking with the sketch in this topic?

Cheers,
Max.

Edit: Sorry, I am mixing up the two topics, this IS the full FHSS topic.

[Phil_G]

Hi Max its a Lidl drill battery cell, an 18650 Lithium-Ion 4.2v charge same as a lipo cell. The 328P is specced down to 1.8v but the guaranteed clocking rate drops proportionally with lower voltage. 4v is slightly below the 4.5v spec for 0-20mhz, and 16mhz is slightly below 20mhz
Its entirely personal choice, whatever you're happy with, thats why the Nano has both power options. The 328P datasheet gives specifics and we're all familiar with battery specs, so for years I've been confidently running many of my models on a single lithium cell. There is never a brownout problem, unlike NiMh the voltage never dips under load because of the very low ESR. Perhaps the servos are slightly slower, I dont notice it, and under load they slow less than NiMh powered servos because of the much larger current capacity of a lithium. The reeds and S/C encoders all use servo slow anyway! Similarly I've loads of domestic 16mhz 328P projects running from a lipo cell. If you feel uncomfortable, use a little 5v BEC, problem solved (if there ever was a problem) If you do use the RF-Nano Vcc though you must remember not to directly connect a 6v NiMh or a 4.8 straight off the charger

I think the range of a pair of RF-Nanos would suffice for a Footy By opening two pipes you could control both from one transmitter


Have a play with both versions Max, they both work fine, at least in model cars and on range checks!
For actual flying (whenever that might be) I will use the FHSS version. The car transmitters have the hybrid software and I'll probably leave them as they are, why change
I've had no issues - no lockups, no unexplained behaviour, no glitches, no random failsafes with either.
I mounted the RF-Nano vertically, so the aerial is in the clear, sticking up into the Junior 60 cabin.
I've not experienced it yet in extensive testing but I expect that in some orientations the PCB aerial might suffer an RF dead spot, so one thing I intend to try is replacing the PCB aerial with a conventional dipole, just to see if that improves the 'visibility' of the receiver - range itself doesnt worry me as the 700 metre test wasnt on the limit - I need to find a longer road
With RF-Nanos at only £3 each theres no harm in trying a couple of 30mm whiskers
I use a lot of Frsky V8R4 receivers, which is a similar situation - single 30mm antenna, no problems, even end on!


For the transmitter, especially smaller ones, here's the 'compact' arrangement of the NRF24L01+PA and its piggy-back adapter board again, taken from the hybrid thread:

They normally fit together like this :

... which is a bit unwieldy - much neater to piggy-back the 5v adapter on top of the NRF:

I've started adding the 100µF tantalum across gnd & 3v3 every time now.


Next week I might get up really early one morning and nip down to Ponty Park for a trial before anyone else turns up. I've quite a few projects to flight-test but I like to do it alone, or you spend all your flying time explaining things and justifying 'why?' to non-believers

Cheers
Phil

[MaxZ]

and justifying 'why?' to non-believers

Yeah, I've read that...
As for single whiskers, I have several of those in use, Multiplex 4/5 and 7 channel receivers. Never had a glitch.

Cheers,
Max.

[bluejets]

Might have to wait until this virus thing passes sufficiently for things to pick up again.

Currently the NRF-Nano is rather scarce down in Aus ( or from China ) and priced around the AU$25.00 mark plus postage which now-a-days comes in at $6 to $7.00 extra.

As for the NRF24L01+, apparently quite a lot of clones, some which work, some don't and although there are marking differences one can refer to to determine which is which to a point, this doesn't seem to be obvious until one has it on hand and actually tries it.

I dare say it will happen with the nano in time.

[MaxZ]

I need some help finding the nRF24L01.h library. I found and installed the RF24 lib. , and I have a feeling it is part of that library, correct?

Cheers,
Max.

[Phil_G]

Here you go Max: viewtopic.php?f=42&t=945&start=10#p7636
Make sure its the TMRh20 library not the older Maniacbug one.
Dont accidentally end up with both, like i did - thats fatal as they use the same file names
Use the IDE menu to install it as a zip library.
Go to http://tmrh20.github.io/RF24/ and scroll down to "Useful References", then click "Download".
The zip contains everything you need. If you cant find it, see attached.
Cheers
Phil

[MaxZ]

Thanks Phil.
I found the RF24 in my Arduino library manager:

And compiling the sketches is ok, so it recognises nRF24L01.h and all is fine.

Cheers,
Max.

[MaxZ]

Just watch CE and CSN, pins D9 and D10 are swapped on the RF-Nano:

Hi Phil,

I am getting a bit confused on the CE,CSN connections, so to confirm, this is how I understand it:

I should use this in both sketches for Tx and Rx, regardless if I am using a Nano RF or a high power module in the Tx:

Schermafbeelding 2020-05-27 om 10.35.45.png (9.99 KiB) Viewed 45272 times

and when I use the high power module, it should be hooked up like so:

Is this correct?

Cheers,
Max.