DIO line passing between microcontrollers

XBee & XBee Gateway
,
1

I am using two 802.15.4 xbees to pass DIO signals between two identical microcontrollers (uC1 and uC2). I am also passing serial data bytes between the uCs which works just fine. I have both xbees setup for AT commands.

I have connected the wiring as follows:
==uC1==========xbee1=====
DIO_out -> p19 (DIO1):in
DIO_in -> p20 (DIO0):out

==uC2==========xbee2=====
DIO_out -> p20(DIO0):in
DIO_in -> p19(DIO1):out

My experiment is to send via DIO_out a 1ms 3.3V pulse from uC1, receive it on uC2, and retransmit it to uC1. This will allow me to compute the precise transport delay of the round trip DIO signals. Dividing by 2 gives me the one-way transport delay.
So far, this isn’t working.

I am using AT commands …
==xbee1=========xbee2===
ATID 3141=====ATID 3141
ATMY 1111=====ATMY 2222
ATDL 2222=====ATDL 1111
ATD0 0x03=====ATD0 0x04
ATD1 0x04=====ATD1 0x03
ATIC 0x03=====ATIC 0x03
ATIC sets bits 0 and 1 for change detection.
I believe, for the 802.15.4 xbee, the ATIC has only a single byte argument.

My question is:
Is this a sufficient set of AT commands for the DIO line passing? I have set ATIC for change detection, so I don’t think I need the ATIR sample rate command. Also, I don’t think I need the ATT0 and ATT1 timeout commands.

Suggestions welcome.
Jim

2

These are sufficient AT commands to enable Line Passing.

Connect these modules to XBIB interface board and check if Line Passing working manually with switches and LEDs of interface board.

If it works then check if DIO lines of micro-controllers have output voltage and output time duration sufficient enough to trigger change detection. These modules requires maximum 0.35* VCC for LOW and minimum 07*VCC to trigger HIGH.

3

I would suggest reading over both http://knowledge.digi.com/articles/Knowledge_Base_Article/XBee-802-15-4-Digital-Input-Output-Line-Passing/?q=DIO+line+passing&l=en_US&fs=Search&pn=1 and http://knowledge.digi.com/articles/Knowledge_Base_Article/Digital-and-analog-sampling-using-XBee-radios/?q=DIO+line+passing&l=en_US&fs=Search&pn=1.

I think you will find that your requested rates are exceeding its capabilities.