Author Topic: MightyHat with RFM95 & radiohead lib  (Read 2613 times)

steve v

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MightyHat with RFM95 & radiohead lib
« on: January 30, 2017, 08:54:22 PM »
I'm trying to get multiple MightHats  to communicate with multiple Moteino RFM95 nodes. At close range 3 meters.

Using the radiohead library.

Out of 6 Mightyhats,  I have 4 MightyHats that work with all of the Moteino nodes, but I have 1 Mightyhat that only work with 3 out of 5 nodes,  and another  MightyHat that works with  4 out of 5 different nodes.

Im using Bw31_25Cr48Sf512

It looks to me like 2 of the nodes and 2 of the  Mightyhats may be off frequency by a few ppm

I have a good HP Lab spectrum analyzer and Frequency meter, is there any test software I can run on the MoteinoRFM95 to get a carrier so I can measure a static frequency ?


Any other suggestions on diagnosing the problem ?




Felix

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Re: MightyHat with RFM95 & radiohead lib
« Reply #1 on: January 31, 2017, 01:45:25 PM »
When you say it works you mean in receiving or transmitting or both?
When I test all MoteinoLoRas and MightyHats with RFM95 I use a MoteinoLoRa receiver, I expect all tested boards to be able to send/receive to that Moteino base. The examples I am using are in my shared RadioHead library (client and server).
The transceiver sending engine is similar to that of the RFM69, maybe you can just put the radio in continuous transmit mode and put a random stream of bits onto it to generate a modulated carrier.

steve v

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Re: MightyHat with RFM95 & radiohead lib
« Reply #2 on: January 31, 2017, 08:25:52 PM »
Thanks Felix,

Yes the device is tested between a Mightyhat and a Moteino Tx and RX.

All the devices will run in a temperature controlled environment about 68-72 F. So I don't need a TCXO

I was hoping to put it in a CW carrier mode.  in the Spread spectrum mode it's hard to get an accurate Frequ reading.

Does anyone have a sample sketch to help me put a LoRa radio into a CW mode ?

I beleive I can also measure the 32MHz xtal, but I need a very low capacitance probe to do that. As it will create a frequency shift on the Pierce Oscillator.  I guess if the probe made all the radios shift the same amount  that would be ok, and I could adjust my Radio frequency accordingly.


perky

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Re: MightyHat with RFM95 & radiohead lib
« Reply #3 on: January 31, 2017, 08:53:59 PM »
Putting any kind of probe on the crystal will detune it, you should instead enable ClkOut on DIO5 and measure that as that won't change the loading. Once you know accurately what your crystal frequency is you can calculate the transmit frequency as it's PLL based and just a multiple of the XTAL frequency.
Mark.

steve v

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Re: MightyHat with RFM95 & radiohead lib
« Reply #4 on: February 01, 2017, 01:33:19 AM »
Thanks Mark,

I think that's the sensible way to go, I'll just monitor the 32.0000xx  Mhz on the DI05

BTW can you point me to a sketch/ example to  configure the DIO5 as a clk output ?