I've use a MoteinoUSB that I use to monitor my home power usage which is setup to do OOK reception (Github:
Powermon433). It works just fine plugged into my main linux computer but it is pretty far from the transmitter so I get dropouts. I decided to plug it into a Pi (still via USB) and have that closer but for some reason I just could not get it to pick up any signal at all.
I took the whole thing back into the lab and hooked it to the oscilloscope to check the pulses received. It worked perfectly. I moved it 6 feet to the left into an available outlet, it stopped working again. Hooked up the oscilloscope, worked perfectly. Then I moved it over to the spare monitor and keyboard I have for working with Pis in my lab. It worked great there, but if I
unplugged the HDMI it would stop receiving again. That got me thinking, the chassis ground of the HDMI connection to the monitor is earth grounded. The oscilloscope probe ground is earth grounded...
Went back to my original Pi location and plugged it in, no reception at all as anticipated. Then I jammed a wire into the 3rd prong grounding hole in the electrical outlet and clipped it to the Moteino ground
DO NOT STICK WIRES INTO ELECTRICAL OUTLETS UNLESS YOU ARE DUMB and it worked perfectly. Unclipped the extra ground, it stopped receiving. It is impossible to see what's going on because the second I hook the oscilloscope to it, it works fine thanks to the grounding.
So what the heck is happening here? How can the RFM69 receiver be completely incapable of receiving OOK unless it is earth grounded? The Pi is a Pi 2, and I've tried all sorts of different shielding setups wrapping both the Pi and the Moteino in aluminum foil then grounding the shield. Could it be the power adapters I have tried the regular 0V grounds on them aren't suitable for powering this? I'm really at a loss as to why it doesn't work
at all when just plugged into a Pi and a 5V supply (nothing else connected).