Watchdog Timer
JDOhio
Posts: 72
I am using the Watchdog timer in a program similar to Bean's Magic 8 program. There is some set up and then it executes:
When the Watchdog times out, the SX comes out of SLEEP and starts the program again.
I am seeing odd behavior in the Watchdog timer when I operate the SX at 3.3 volts. At 5 volts, the program operates as expected. At 3.3 volts, I have seen longer than expected time outs (I am using the maximum of 2 seconds - I have seen 3 and longer), and I have seen the program hang when the Watchdog should rescue it. The only difference I see is the supply voltage. Any ideas?
Joe
RESETWDT SLEEP
When the Watchdog times out, the SX comes out of SLEEP and starts the program again.
I am seeing odd behavior in the Watchdog timer when I operate the SX at 3.3 volts. At 5 volts, the program operates as expected. At 3.3 volts, I have seen longer than expected time outs (I am using the maximum of 2 seconds - I have seen 3 and longer), and I have seen the program hang when the Watchdog should rescue it. The only difference I see is the supply voltage. Any ideas?
Joe
Comments
I have not tried it at 3.3volts, but the watchdog timer is VERY inaccurate. And very sensitive to temperature and supply voltage. (In fact I've seen programs that measure temperature using the watchdog timer compared to a resonator).
50% error sounds really high though.
Bean.
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I am going to try waking the SX with a 555 timer in monostable mode through Port B. I want to do this to determine if there is a coding issue and to have a little better accuracy - I need two seconds but three kind of concerns me. My application is for high altitude ballooning and I won't be able to troubleshoot at 100k feet. A sleeping processor would prevent both sensor data logging and picture taking.
Joe