💬 Connecting the Radio

[manutremo]

I have two of my nodes using rfm69hw and mini pro 5v 17mhz. I only step down the power line to 3.3v, the comms lines work just fine with 5v. I also remember reading somewhere that this is actually the case, even though the datasheet says the opposite.

[gohan]

I'd follow the datasheet and don't take the risk of frying the radio.

[manutremo]

They've been working for more than 6 months now as part of a test run and are not yet fried.

There is other people around reporting the same with at least the rfm69HW. I remember someone stating that the new models are more robust in this regard than older models, in spite of the manufacturer not yet stating 5v tolerance in the data pins.

In fact the datasheet never mentions 5v intolerance, and it does never actually mention a max voltage for the data pins, only for Vdd.

It seems like the board does something with the voltages in the data pins anyways, since if it was using the definitions of the logic levels (as a percent of Vdd) as they appear in the datasheet, it should not be able to communicate at all with a 5v arduino when powered at 3.3v and no logic level shifter on the data pins - but it does.

This doesn't mean this is good practice, directions in the datasheet are there for some reason and my nodes will eventually get a logic level shifter when they finally go into their final case. But reality is it seems at least RFM69HW can tolerate 5v for months without being fried.

[gohan]

still I would not advise someone to go ahead and use them without a level shifter as I would not take responsibility to damage someone else hardware 3.3V is still able to talk to 5V, depends on how large is the tolerance zone around the 2.5V grey zone of the arduino

[manutremo]

I would not expect anyone to put or take responsability on anyone for a piece of advice. I think we are here to help each other by sharing information and our own experiences.

The full picture should be more than clear at this point for anyone reading this and other threads, but I will clarify once more. Best practice is using the rfm69 family with a logic level converter when connected with a 5v arduino, given that as of today the manufacturer's datasheet is not 100% clear on this area. From a problem solving perspective, keep in mind, however, that should a converter not be in place for any reason, the setup might or might not work, so if it doesn't don't discard it as a cause but don't take it for granted at 100%. And even if it works, do plan for adding a converter.

[jkandasa]

@hek @mfalkvidd RFM95 radio part connection details are missing.

[maghac]

Is it possible to change any of the radio pins 9, 10, 11 to something else? The reason is that I'd like to use 4 PWM pins and currently I only have pins 3,5,6 available on my Pro Mini.

[mfalkvidd]

@maghac yes. Redefining for example the nss/cs pin is possible as described on the connecting the radio page.

For more exact i structions we'd need to know which radio you are using.

[maghac]

Thanks - I use NRF24 radios.

I found MY_RF24_CE_PIN which I redefined to pin 8 which worked absolutely fine.

The problem I have now is that now cannot use the Newbie PCB anymore :cold_sweat: :wink:

[mfalkvidd]

@maghac doh!
How about using a software pwm library instead? I have not tried any, but I have seen this before: https://github.com/Palatis/arduino-softpwm

[sundberg84]

@maghac cut the trace with a small knife and re-attach it with a wire.

[maghac]

@mfalkvidd Maybe I'll give that a try.

I think FOTA will fail as the bootloader will try to initialise the radio with the default pin, right? Then I'll need software pwm or recompile my own bootloader.

[gohan]

@maghac or go for dual optiboot

[maghac]

@gohan But then I would need additional hardware to use DualOptiBoot?

Anyone have any quick instructions on how to build a new custom version of MySensorsBootLoader using MY_RF24_CE_PIN = 8 :wink:

I have access to ArduinoIDE on Windows or a Ubuntu 16.04 box.

[gohan]

@maghac yes, an spi flash chip. It is not a bad solution since the firmware is transferred during normal node operation and if it fails nothing bad happens.

[sundberg84]

@maghac - EasyPCB rev 10 will probably include spi flash ;)

[alowhum]

It might be an idea for the "connecting the radio" page on MySensors to point to these handy boards:
https://www.aliexpress.com/item/Free-shipping-Nano-328P-IO-wireless-sensor-expansion-board-for-XBEE-and-NRF24L01-Socket-for-arduino/32298692903.html

Then people have to just plug in the NRF24 boards. And it also makes it much easier to connect lots of sensors. I wish I had known about these boards earlier, it would have saved me a lot of time.

[gohan]

It depends if you want to go with the nano or the pro mini like many nodes use

[KimmoHop]

Just noticed, that MySensors 2.2 changed default RF24 CS pin on Mega2560 from pin 10 to pin 53 (SS) :/ I could not find any reference to the change from 2.2 change log nor from pull request (722)... No wonder RF24 worked with 2.1.1 but not with 2.2 on M2560.
Contrary to instruction above, I wanted to continue with old pins (same as on Uno) and set the pins explicitly to MY_RF24_CE_PIN=9 & MY_RF24_CS_PIN=10. Now transport seems quite good (with combined HW and SW ack, static GW address, no routers) :)

[mfalkvidd]

@kimmohop thanks for reporting. Looks like the change was introduced in commit b132a8a81e2ba6c81bcc6e2afce7513cdddbe193. I have added a message to the release notes.