67: Extending My Pi
* revised 23 Dec 2014 *

In my last post I wrote about adding a front-end Arduino Nano to handle analog input. And that works fine but it doesn't do much for extending sensor distances. I.e., USB 2.0 is limited to 16' cables. So here's my next cut. I added another Nano and a pair of nRF24L01+ tranceivers.

I know, it's messy but the price isn't bad: the Nanos are $14 each and the pair of RF24s were under $10. And the "receiver" Nano can service multiple "senders." 

I used the maniacbug.github.io/RF24/ software. It works but documentation is lacking. I wasted 2 days getting a working setup and there are still mysteries. About par for the course. 

Dec 23: Below is a pic of my transmitting RF24 (Nano in background). With just the builtin antenna I got about 50' indoors (through a wall and my body) before loosing a packet. Had to retry every other packet at 100' indoors to outdoors through 2 walls and an evergreen. Through my body made it worse. Line-of-sight 200' is probably reasonable. But the RF24s with screw-on antennas seem worth it ($20/pair).

nRF24L01+

I have an idle Pi B+ with extra pins, so I'll try using it in place of the "receiver" Nano. The RF 24 uses 5 GPIOs plus 3.3v and ground.