[Alan Anderson]

Kevin's code puts the camera in "raw" mode, which does not want the '\r' after the parameters. The first byte after the command (here it's a 1) says how many more bytes will follow. I'm pretty sure an extraneous return at that point will have a real chance of waking the camera up immediately after you tell it to sleep.

I don't have a camera handy to test whether or not an ACK comes back after a sleep command, but it's easy for you to connect the camera serial port directly to a terminal and try it for yourself.