> Anyone know where to find or how to figure out the startup time for 
> an IR
> receiver module?   (I'm using the TSOP4838 in this case).

It's going to be extremely product dependent and quite likely not in 
most data sheets. Some testing yourself is liable to be required as 
its not usually something the makers characterise. It's easy enough to 
do it yourself. Power on the RX and send data a variable period 
thereafter and monitor the output. Biggest trap is liable to be to get 
a result which is truly representative of worst case results, which is 
what you want.

You may be better off finding a module that has a low power standby 
mode and an enable input to reduce latency (but I don't know if these 
exist) .

This may be an occasion when rolling your own makes sense. It seldom 
does otherwise.
The TSSOP4838 draws around 1 mA. I'd have thought a careful discrete 
design could easily enough reduce that by an order of magnitude when 
running.

You could consider synchronising transmitter and receiver to eg 1 
second boundaries so the PIC wakes up at potential transmission time. 
You could arrange so transmission always occurs after N cycles to 
allow occasional clock resyncing.




        RM

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