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coin cell powered rfm69 module
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mmrvelj:
I am trying to build low power (coin cell CR2032 powered) simple device that would be used to transmit occasional messages (pushbutton or beacon) by using RFM69 module.

For this I have selected to use ATmega328p MCU mainly because I have (some) experience with it.

I did manage to have a working setup, however only when I power the device externally. It is not working when powered with CR2032 (because it draws too much current). I am still trying to figure out why, I will start debugging tonight, however I would appreciate if someone with more experience could take a look at my schematic and comment if there are obvious design flaws.

I am measuring current consumption of around 40mA  :o , although I am putting ATmega and RFM69 to low power modes (using LowPower library for ATMega and radio.sleep for RFM69).
mmrvelj:
Update, with RFM69 disconnected I measure rest of the board sleeping at 18uA. So probably I am not putting RFM69 to sleep properly..
viperidae:
40mA is quite a bit for the RFM69. It's only supposed to draw that much power in transmit mode. The datasheet says 33mA at +10dBm.

You're also probably going to get up to 1V drop from the internal resistance of the CR2032 if you pull 50mA while transmitting, assuming 20R.
Rolo:
Also check at what brown-out voltage your ATmega is set, as said the internal resistance of these coin cells give a drop in Vcc, if it's goes under your BOD voltage your mcu will stop working or give unexpected behavior.
I'm using mysensors node's with the RFM69W and have sleep currents of 6 uA, with no other sensors attached, just an atmega and the radio module. So a good sleep is possible.
mmrvelj:
Thanks, I am guessing that I might have messed up something in software part (at least I am hoping). ATMega BOD is set to 1.8V, I hope this should be good enough?

I know there are similar designs that do work with CR2032, so in theory, it should be possible :)
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