We updated the white paper for the infrared subsystem:

http://neo900.org/stuff/papers/ir.pdf

The main changes:
- defined the placement of the IR diodes: section 5,
- changed the photodiode to VEMD10940F due to size constraints,
- defined (and simplified) the IR RX circuit: sections 2.6 and 9, and
- simplified and clarified the control inputs (e.g., bq.GPIO is all the receiver needs, and "CPU off" simply means that the whole system is powered down).

This specific version is at
http://neo900.org/stuff/papers/ir-20150314.pdf

The source can be found at
http://neo900.org/git/?p=misc;a=tree;f=ir

- Werner