Wireless choice (Xbee/Parallax 433MHz) for BS2 communication project

xanatos

Hi folks,

I've taken on a project that is somewhat ambitious for me.· The project requires that a small packet of data be sent from a "local" BS2 system (probably BS2SX) to a "remote" unit (also BS2SX...· I just like 'em).· The packet will consist of a sequence of ·"unit ID numbers" that will be active/inactive by a single bit setting.· This data packet will·be sent·endlessly every minute, so that when the master unit's timekeeper function sees the time end for a given unit, it will change that unit's active bit to 0.· The remote unit will receive this data and activate the units that have a 1 "active" bit, and keep them active until they get a zero in the active bit.· The remote unit could be anywhere from 150' to 300' from the local unit (across an open field).

I have been looking at the XBee Pro and the Parallax 433mHz units.· Both appear to do what I want, but my gut feeling is that the Parallax units are probably more well suited to my application.

I'd really appreciate any thoughts ye wise ones have on the issue.· I'm relatively new to microcontrollers, but I've come VERY far very fast, so I am confident that if I have the right hardware and a few pertinent code examples, I can make this happen.

Thanks VERY much!

Dave X

·

Mike Green

The xBee devices take care of error checking and retransmission. The Parallax devices do not. That's not a big deal, but you do have to add some kind of error checking. Since the information is retransmitted regardless about once a minute, you don't need any kind of retransmission on error, but you have to check to make sure the packet is valid. I suggest sending two copies of the data in a packet and ignoring it on the receiving end if the copies don't match.

xanatos

The duplicate packet idea is good. I could also send a "checksum" of sorts that was the decimal equivalent of the 0s and 1s I'm sending, so if 00001001 (the on/off states of the units) equals anything other than 9, ignore the packet. I'm trying to avoid two-way comm if possible, just one way from local to remote, and putting code into the remote to make it relatively fault tolerant. Thanks for the tip on that.