💬 Connecting the Radio

[mfalkvidd]

@Grave thanks for pointing this out. From looking at the source code, it looks like it should be MY_RFM69_CS_PIN. I have updated the text. Could you check if I got it right?

[Grave]

Thanks, you are right.

[joseyapor]

which one is better RFM69 or NRF24L01+

[gohan]

The problem is that nrf24 have many crappy clones that have limited range and it is difficult to find the original ones. Rfm69 is slower but have better wall penetration and modules come in 3 frequencies.

[sundberg84]

Nrf24l01+ also drains less current when sleeping vs RFM69

[mfalkvidd]

@joseyapor neither is better. They are good at different things. See https://forum.mysensors.org/topic/3993/nordic-or-hoperf-radio/2 for an earlier discussion.

[RAD-X]

@mfalkvidd said in 💬 Connecting the Radio:

@Grave thanks for pointing this out. From looking at the source code, it looks like it should be MY_RFM69_CS_PIN. I have updated the text. Could you check if I got it right?

It looks like that MY_RFM69_CS_PIN is used only in develop branch.
Stable brach still using MY_RF69_SPI_CS.

[mfalkvidd]

@RAD-X both will work in the stable branch. See https://github.com/mysensors/MySensors/blob/28c4f3f19e7026f56fd9bbc61d566f770fd7a9d2/MyConfig.h#L935

[RAD-X]

@mfalkvidd
Hmm.... Is not that a reference to the development branch? :-)
I think that right content for stable branch is: https://github.com/mysensors/MySensors/blob/master/MyConfig.h
If you don´t believe it, try to download a stable branch, unpack and search for string "MY_RFM69_CS_PIN".

[mfalkvidd]

@RAD-X yes, you are correct. Thanks for noticing.

I thought that if I selected the master branch on github and used the search function, the search results would only show hits from the selected branch. But it seems like this is not the case.

Linking to a specific line in a file doesn't work very well, because that line might move by later commits. That's why I select a specific commit to link to. But as you point out, my link points to a commit in the development branch.

The correct link is https://github.com/mysensors/MySensors/blob/8bb3cfb2e14214ae19e8531c989d1e81c9660614/MyConfig.h#L663 and there is indeed no support for MY_RFM69_CS_PIN.

I'll update the documentation again. The documentation is meant to reflect the current stable branch.

EDIT: Found this in the Github documentation:

Only the default branch is considered.

So there is no way to search in the stable branch.

[manutremo]

I have one question regarding the length of the 868MHz antenna. According to the theory, a the wavelength of a 868Mhz signal is 300/868 = 34.6 mm, so a quarter wave antenna should be 8.6mm long. The table above indicates 8.2mm. May someone confirm the correct figure, and also indicate how critical is that difference in terms of range?

[mfalkvidd]

@manutremo the speed of electromagnetic waves is slower in metal than in vacuum, that's why the length is shorter.

My experience is that the length doesn't need to be exact, but antenna theory is way too complicated for me to understand the details.

[manutremo]

Many thanks @mfalkvidd . That explains it.

While waiting for an answer I also found some sites which mention that the speed of electromagnetic waves is even slower if the conductor has an isolation layer around, which would further justify the difference.

Many thanks! :+1:

[mfalkvidd]

@manutremo I think that part is due to skin effect.

[manutremo]

@mfalkvidd Many thanks again... I learn new things every day.

[gvorster]

@manutremo said in 💬 Connecting the Radio:

I have one question regarding the length of the 868MHz antenna. According to the theory, a the wavelength of a 868Mhz signal is 300/868 = 34.6 mm, so a quarter wave antenna should be 8.6mm long. The table above indicates 8.2mm. May someone confirm the correct figure, and also indicate how critical is that difference in terms of range?

I tried 3 types of antennas with RFM69HCW 868mhz.

1. Just a 8.6 cm wire

2. helical antenna

3. sma antenna

Indoor in my appartement (one floor) it doesn't matter which one I use. All is working fine.
I tried 2 nodes in my metal mailbox 10 meters below which has 2 tiny holes.
One with helical antenna, one with sma antenna.

Gateway (using sma antenna) receives no data.

Testing two repeater nodes (1 helical, 1 sma antenna) near a window I receive data via both repeaters. Sometimes the repeater with sma antenna is not relaying messages for the node with the sma antenna.

In my situation, the helical antenna works better for me. I just buy them on ebay.

[gohan]

Maybe the sma antenna is for the wrong frequency and it's giving poor results.

[krisha]

There is a mini module of the NRF 24L01+. Unfortunately some pinouts on the web were not correct. Not sure if many people use that, but here is a pinout that worked for me: http://s2.electrodragon.com/wp-content/uploads/2014/12/NRF24-Mini-02.jpg

[manul]

Hi Team,

First of all, thank you for your amazing work! It does help a lot to sea a dream become true :)

I was wondering, it seems that I can't receive messages from NRF24 radio while arduino node is sleeping... I've read several testimonies in this way as well on forums. I did connect the IRQ of the transceiver to the PIN 2 of my arduino, and took this as event for exiting sleep mode, but it seems not to work.

Is there anything in the roadmap regarding this? It could be really amazing to be able to sleep the battery-powered arduino, and wake it up as soon a message is received by the radio.
Or maybe there is something I did not correctly. Is there a feature for this?

[mfalkvidd]

@manul it would indeed be amazing, but the radios consume so much power when listening that it is no use to sleep the mcu.

The smartsleep feature is the best alternative so far. documentation: https://www.mysensors.org/download/sensor_api_20#sleeping