XBee 2 sleep mode / initial wake-up


I have two Xbee S2, first one running as a coordinator in API mode, second one as a router in AT mode.

The router reads an analog value (temp sensor) on its AD3 and sends the value to the coordinator. Please note that this works fine… until I setup some sleep options.

Now I want to introduce some sleep mode on the router to save battery power. I want it to sleep for 5 minutes, wake up, send on frame with the AD3 sample, then go back to sleep again.

Here are the router settings I’m using:

SM = 0x4
SP = 0x3E8 (=10s)
SN = 0x1E (=30, such that total sleep time is 30x10s = 5min)
ST = 0x1F4 (=500ms, should be sufficient to read analog value and send it to the coordinator…)
SO = 0x6
D3 = 0x2
IR = 0x1388 (=5s, so it has only time to send one sample before it goes to sleep again)

This doesn’t work: when I power on the router, it simply sends nothing and it doesn’t either wake up after 5 minutes (or so do I think as I don’t receive any frame at the coordinator).

I’ve read there and there that the XBee needs some time to initially join the network… so would 500ms of wake time be sufficient ? Is there some special initial conditions to meet ?

Thanks for your help.

May I suggest reading over http://knowledge.digi.com/articles/Knowledge_Base_Article/XBee-Cyclic-Sleep-Example-Indirect-Messaging first. Also I would suggest starting with a short sleep cycle. Say 30 seconds.

The wake time also only needs to be 20 - 100ms at most. This is more than enough time for the radio to sample its ADC input and transmit the data.