questions about RFM69Pi


Just looking at schematic and board for RFM69PI_v3 compared to the RFM12pi V2 and have some questions.

Are you downgrading to Atmega168 instead of the 328 or is just your symbol in the schematic?

Do you have any plans with the extra pins from the atmega?

Whats the Crystal value? 16MHz?

And a tip. If you are able to shrink the width to be less than 25mm you can have more on the same board, lowering the price. It looks like its possible if you turn the radio 90 degrees.


merry Xmas

glyn.hudson's picture

Re: questions about RFM69Pi

Hi Haden, 

No, we're not downgrading, that's just the symbol in the schematic. The pinout is identical. 

The xtra pins could be used for connecting to ds18b20 sensors or control relays. We have no immediate plans however we plan to use the unit as a building block for more modules in the future. Having more io broken out is never a bad thing! 

Yes the crystal value is 16mhz, however we plan to use the internal 8mhz oscillator as standard, the 16mhz crystal can be fitted as required. 

​I will investigate if further shrinkage is possible, however routing the board was quite a challenge with two layers in it's current size! 

haden's picture

Re: questions about RFM69Pi

Hi Glyn

Thanks for answers. I'll take a look in the shrink process too. It might be possible, at least if the length is extended a little. Usually the PCB shops has boardsizes that are 5 or 10 cm width, so right now there is some waste. I don't know if it affect the price in big orders, but for the hobbyist it can make a difference. Changing the schematic to have the right parts makes it easy to extract a BOM



dBC's picture

Re: questions about RFM69Pi

however we plan to use the internal 8mhz oscillator as standard

Do you plan to calibrate each AVR's RC oscillator at production time as per AVR053?  I think it varies a bit from AVR model to AVR model, but in general the factory calibration is only good for about +/- 10%.  That'll impact all the timers (delay(), millis(), micros() etc) and more importantly, it messes up the baud rate generation for serial comms.

I'm not really up to speed on all your different OEM models, but I do recall seeing some baud rate weirdness being discussed recently.  Normally an 8MHz AVR has no problem generating a 57600 baud clock (the 3% error is usually acceptable), but I think your chances would be greatly reduced if you were still running with the factory calibration on the RC oscillator.

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