XBee Shield won't reset Mega 2560 with UART switch

Wireless & IoT
1

Hello,

I’ve created an Xbee Series 2 wireless sensor network. It works fine except that I cannot reliably reset the main coordinator Arduino. This is a Mega 2560 with a Sparkfun XBee Shield hosting a Series 2 XBee. When the shield switch is set to “UART” for wireless RX/TX, a hard reset or EVEN a power cycle will usually not reset the program (80% of the time).

I’ve been able to repeat this with the “Blink” demo program and verify that this problem does not exist when the shield is plugged into an Uno.

Any thoughts are welcome.

2

I should add that when I say it’s won’t reset the arduino…it doesn’t ignore the reset. The arduino just locks up. I have idea what state its in.

3

Does the “reset” Toggle the reset pin of the processor (Mega 2560) properly?

Check that with a scope. Check the Mega 2560’s data sheet for the proper ‘reset’ voltage levels and rise/fall times.

4

Unfortunately I’m 800 miles away from my scope :frowning: I’m thinking the xbee is holding the RX high, which might be preventing the reset.

Thanks