HeaterMeter being overclocked?


 

DavidNP

TVWBB Member
Hey, I've finally assembled my first HM....considering my soldering-skills I'd say it went well....but it was definitely not 'easy'....but powered on and worked :) Hardest part was that my at328p chip couldn't be easily programmed (not using a Pi)...but after a bit of research I got to flash the device.

One thing I noticed is that HeaterMeters atmega328p is running at 3.3v but at 16hz...Am I wrong? If it is running 3.3/16hz then that is out-of-spec and a is a no-no.....random issues outside room-temperature are possible..etc...

http://electronics.stackexchange.com/questions/21598/overclocking-an-avr

I may be totally wrong...I'm a software guy....someone with more hardware knowledge would know better....
 
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You're right, it is out of spec to run the ATmega328 at 16MHz at 3.3V. However it is pretty close-- the actual voltage you'd need to operate in spec is 3.78V, or 13.3MHz at 3.3V. There are tons of projects that use the ATmega at 16MHz and 3.3V so I just assumed it was safe enough. In practice I haven't seen any mystery weirdness that occurred apart from bad code I've written.

Ideally it would run at 12MHz but a lot of the Arduino code expects either 8MHz or 16MHz so it wouldn't work right. I run HeaterMeters continuously around the lab and they never lock up or reboot that I can tell, and drive all their pins in the manner we've designed around. I think if it were a problem we'd have seen it by now.
 

 

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