Xbee S3B CTS pin stays high


The problem I’m having seems a bit weird. I have two different types of customized PCB (A & B) with xbee socket, and a bunch of USB xbee adapter. Among the 7 xbee S3b radios I have, 2 of them would work perfectly fine when installed on both PCB A and B, or USB adapter. But the rest 5 radios won’t work at all when installed on PCB A, but works perfectly fine when installed on PCB B and USB adapter. Further investigation indicates that CTS pin of those xbee radios stays high when they are installed on PCB A.

I have tried firmware version 8074 and 8075. Upgrading firmware didn’t make a difference.

Could anybody point me to some directions for troubleshooting? One possible reason is, those 5 radios were damaged at some point somehow. But this explanation is not quite satisfactory.

Thanks in advance.

No that issue of them being damaged is a real possibility. What happens when you connect them to an XBIB interface board?

Those module do seem have been damaged somehow to some degree at some point. I tested 5 brand new modules on PCB A on which 5 old modules didn’t work, all new modules work just fine.

But still, this puzzles me. Those damaged modules work just fine on XBIB interface board, my other customized PCBs.

What I would do is first is do a restore to the radios firmware and then see if I can still talk to it. If I can, the I know it was a setting that was causing the issues.

I can talk to those supposedly damaged modules from computer when they are installed on XBIB or my own USB adapters with no problems. The only problem is, when they are installed on one of my customized PCB, CTS pin stays high, and of course, there is no way to communicate with them. It is rather weird.

That would tell me that you have an a strong pull up resistor on that like and possibly other issues with the board.