This circuit allows many uses :
It runs from battery. There is a CR2032 holder on bottom, but it can also be powered with 2xAA batteries, on a separate header.
You can also directly provide the 3.3V on another header.
There is 2 inputs : both have pull-ups pads to solder a resistor, but are optionnal (if you prefer to use atmega internal resistor).
The power stage uses a MAX1724EZK33+, which converts input voltage from 0.8V to 3.3V to fixed output of 3.3V.
The radio module used is a RFM69(HW). I also made a very similar version for the RFM69HCW, because HopeRF did a mistake and sold me 50pcs of the wrong radio module ;). It uses almost the same components, except I removed the boost converter.
Circuit size is 50x30mm, which is about the same size of 2xAA batteries. You can the place it almost everywhere !
**Component selection ** There is different ways to power this device :
Programming Warning ! The board isn't drilled big enough to use standard ICSP headers ! Instead, I made a simple adapter with pogo pins (pictures coming soon). Just hold the adapter with a hand firmly on the board, and hit "upload" with your second hand. You'll also need an USBASP or equivalent programmer (no USB adapter on the board !)
** Usage ** You can use the device multiple ways :
|Qty||Value||Device||Package||Parts||Description||MF||MPN||Aliexpress or Ebay link|
|1||RFM69HW||Or RFM69W if you don't care about high power.|
|6||Pogo Pins||to use ICSP !|
|1||AMS1117||...or equivalent, if you plan to supply more than 4.5V|
|1||MAX1724EZK33||if you plan to power with less than 3V|
|1||1206 inductor 10uH||if you plan to power with less than 3V||Ebay: http://www.ebay.fr/itm/162095805639?_trksid=p2057872.m...|
|1||CR2032 holder||if you plan to power with a coin cell||Ebay: https://www.ebay.fr/p/2099692115?iid=222345648032|