I built up this project http://www.ulrichradig.de/ and RFM22 und ein ATmega and after some time trying to get them to work I suddenly realised a potential gotcha.
Even though I am running my ATmega88 off a 3V3 supply I didn't stop and think what happened when I programmed the system. My USB programmer, via the ISP places 5Volts on the RFM22B (max 3.6V)!
It appears that the intention is to program this board via the ISP, so how does one safely program the ATmega88 while this 3V3 peripheral is attached?
Are there ISP programmers with 3V3 output or should I just disconnect the RFM22B while programming?