RFM73 experience

[Yveaux]

Looking at the RadioHead driver (http://forum.mysensors.org/topic/285/porting-mysensors-to-work-with-the-radiohead-library) I stumbled upon the RFM73 module from HopeRF (http://www.hoperf.com/rf/2.4g_module/RFM73.htm).

It seems to be a Chinese clone of the nRF24L01+ from Nordic Semiconductors, but the datasheet & the RadioHead implementation suggest they should be compatible.

They appear to be a bit more expensive (roughly $3 a piece) but are a lot smaller (12.8x16.8mm vs. 15x29mm) than the modules we're all used to.

Does anyone have experience with the RFM73 (e.g. compatibility, range) ?

[Damme]

@Yveaux found one difference so far
rfm73: Programmable frequency range 2400-2483.5MHz, 83 channels selectable
nrf24: nRF24L01 can operate on frequencies from 2.400GHz to 2.525GHz

[Yveaux]

@Damme OK, thanks. Did you ever use one?

[Damme]

@Yveaux nope, just looked at it

[Damme]

http://www.ebay.com/itm/Mini-NRF24L01-SMD-1-27MM-wireless-transceiver-module-Small-Size-/400489040899?pt=LH_DefaultDomain_0&hash=item5d3f01cc03

12x18mm

[Yveaux]

@Damme true, forgot about those.

[Zeph]

IIRC the FM73 has a bit higher power than the non-PA nRF. There were a few additional registers I think. I've been wondering how intercompatible they would really turn out to be.

Note that anarduino has a board which is similar to an Arduino Pro Mini, but which accepts the FM73 surface mount radio, for a reasonable price.

[ToSa]

I've used these in the past - mainly due to their size (half of the nRF24 or even less). They are "almost" compatible but you need to tweak the code in some areas to make it work - mainly the initialization differs quite a bit.

[Yveaux]

@ToSa Great you actually used some! Any experience on range wrt nRF24L01?

[ToSa]

I used them a long time ago and they actually never left my desk where I did initial coding and debugging so I don't have real world range experience :( as far as I remember from the specs the range should be slightly better than the nRF24.

[Zeph]

@ToSa

Did you by any chance find out whether it's really limited to 83 channels vs the 127 of the nRF24L01+?

[ToSa]

@Zeph said:

@ToSa

Did you by any chance find out whether it's really limited to 83 channels vs the 127 of the nRF24L01+?

I don't remember that part, sorry. I played with these radios about two years ago :(

If anybody is interested in the code I've re-uploaded it to GIT. It's pretty much un-documented and I would need to look at it to answer detailed questions but it's including some of the features we just started talking about (time/date awareness / pin-by-pin configuration vs. node type / ...). The big difference to MySensors is that it was meant to run one and the same firmware on all nodes no matter what the hardware configuration looks like and the firmware is highly configurable... I still have some documentation about that part if anybody is interested... I stopped the development for two reasons: not enough time and the limitations of the hardware. For a setup like this you probably need to move to something like the ATmega256RFR2.

https://github.com/ToSa27/RfMesh

[Zeph]

Thanks ToSa.

If anybody else plays with the RFM73, please see if it can use channels above 83, as the nRF24L01+ does.

Like the nRF24L01 can use 2 byte addresses tho it's not documented (probably because there are too many false hits). Not documenting channels above 83 would be for different reasons.

[Yveaux]

FYI: RadioHead library 1.34 has some specific initialization code for RFM73 in the nRF24 driver (e.g. ACTIVATE command).
See https://github.com/Yveaux/RadioHead/commit/f895ba933950681234d714fd7c3d3c18658b8ed5