RFM69HW @ 300Kbs

[oric_dan]

I did a search didn't see anything on this. I am just wondering whether anyone has experience running the RFM69HW radios at the max modulation frequency of 300Kbs, and how the results were, and what problems might be seen, and what distances might have been achieved.

I was mainly interested in the possibility of transmitting video images, say, on my Moteino-based security system over a distance of about 80-100 feet. I wouldn't expect anything close to real-time video, of course, but would be nice not to have to wait 10+ sec for every image transfer.

Jpeg might be used on the transmitting end, say using an Arducam-Mini, which I am beginning to experiment with, but  it might take a while to decode jpeg on the receiving end, and then display to LCD, at least using a regular Arduino. So, just wondering out loud, :-).

[emjay]

oric_dan,

Is this use case compatible with the ISM band regulations at your location?
You probably need to look above 1GHz at WiFi et.al. for this.

[joelucid]

I usually use 200kbit for software downloads. With an rfm69hw I've used these settings successfully over the distances you describe. I initially also had 300kbit settings - but that (or even the 200kbit) was faster than the 328p can flash - even if I flash asynchronously while waiting for new packets - so I threw it out.

In case you want to play around with it these were the settings I had used at 300kbit:

  { RF_BITRATEMSB_300000, RF_BITRATELSB_300000,
   RF_FDEVMSB_100000, RF_FDEVLSB_100000,
   RF_RXBW_DCCFREQ_000 | RF_RXBW_MANT_16 | RF_RXBW_EXP_0 },

And this is what works very well with 200kbit:

  { RF_BITRATEMSB_200000, RF_BITRATELSB_200000,
   RF_FDEVMSB_100000, RF_FDEVLSB_100000,
   RF_RXBW_DCCFREQ_000 | RF_RXBW_MANT_16 | RF_RXBW_EXP_0},

Joe

[oric_dan]

@emjay, actually I should try using wifi, but don't think it would work very well at those distances, plus I live in a condo complex, and there are 30 other routers that I pick up - lots of interference. I was mainly interested in hearing about people's possible experiences trying high transfer rates using the RFM radios. I also want it to go to inside the car, and the signals are somewhat attenuated.
https://lowpowerlab.com/forum/index.php/topic,1494.0.html

@joe, thanks for the radio setting info, will save me some initial work, :-). I'll try some experiments with those, and see how it goes out to my carport.  I can capture images from the Arducam-Mini, and throttle transfer out the radio link. The Arducam has an image buffer, so you needn't read out data at video rates.

In case anyone is interested, I wrote a sketch a bit ago to write Arducam images to LCD on the Arduino, so it can deal with somewhat slow processors.
http://forum.arduino.cc/index.php?topic=377651

[ChemE]

I figured I'd necro this thread rather than opening a new one for a RFM69W...

Does anyone have any settings for the RFM69W at 300kbs?  I can get reliable comms at 250k with the following settings:

{ REG_BITRATEMSB, RF_BITRATEMSB_250000},
{ REG_BITRATELSB, RF_BITRATELSB_250000},
{ REG_FDEVMSB, RF_FDEVMSB_50000},
{ REG_FDEVLSB, RF_FDEVLSB_50000},
{ REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_16 | RF_RXBW_EXP_2 },

which are nothing more than the default setting in Felix's library except with the baud rate turned from 55,555 to 250,000.  I have tried the following settings with no success with the same two radios:

{ REG_BITRATEMSB, RF_BITRATEMSB_300000},
{ REG_BITRATELSB, RF_BITRATELSB_300000},
{ REG_FDEVMSB, RF_FDEVMSB_100000},
{ REG_FDEVLSB, RF_FDEVLSB_100000},
{ REG_RXBW, RF_RXBW_DCCFREQ_000 | RF_RXBW_MANT_16 | RF_RXBW_EXP_0 },

which worked for joelucid on his HW

[perky]

You might want to look at this thread, there are some rules you need to follow for setting Fdev and RxBw (and RxBwAfc):
https://lowpowerlab.com/forum/rf-range-antennas-rfm69-library/changing-the-rmf69hcw-configuration-and-back/15/
Mark.

BTW I would question using DccFreq setting of 000 when using such a low modulation index. Most of the energy of the signal is concentrated around the centre frequency and this is setting the DCC cutoff to 16% of RxBw, I'd be tempted to make that 110 to give 0.25%, even 111 for 0.125%.

[ChemE]

Thanks perky, I've read that thread as well as a few others and tried to adhere to those four rules (not using ATC).  I came up with an Fdev of 75,000 and a RxBw of 600,000.  The datasheet makes it look like 500,000 RxBw is the max and that is with the settings I posted unless I misunderstood that table (very possible) in the datasheet.

[ChemE]

For the sake of completeness I tried Dcc cut off frequencies of 4% (default according to the spec sheet), 0.25%, and 0.125% all with a BR of 300k and a RxBw of 500k (the max I believe) and no love.  Maybe there is another setting that needs to be changed besides the few I'm tinkering with?

[perky]

As a matter of interest did you try a higher modulation index? Since you've set RxBw to 500kHz anyway you can use an Fdev of 300kHz, that'll give an MI of 2 and you'll avoid any low beta issues.
Mark.

[ChemE]

Excellent and thank you so much!  Leaving everything else the same and moving to an Fdev of 300,000 worked.  I now get the same RSSI I was getting at 250kbs (-27 at power level 31 with the two radios inches apart).  I'll test a bit and then make sure to summarize the settings concisely for others.  Thanks again!