OpenMV power supply issue

Discussion related to "under the hood" OpenMV topics.
SP097
Posts: 17
Joined: Fri Jan 26, 2018 12:09 am

OpenMV power supply issue

Postby SP097 » Sun Feb 18, 2018 8:01 am

Hi,
I am running a DC motor through an H-Bridge with an OpenMV, which is powered through an external 7.2V, 1200 maH battery which is regulated down to safe Vin levels through a regulator.
This is the H-Bridge IC I am using: https://www.pololu.com/file/0J504/vnh5019.pdf
For fast deceleration and acceleration, the code can plug the motor and reverse the polarity again shortly after.
When this happens, at times, the openMV switches off but the peripheral timers remain active.
I know this because I toggle LEDs in each iteration in my loop and some polarity reversals switch off all the LEDs and lock the two PWM signals I am using.
The problem ceases to exist when I increase the delay between 2 consecutive polarity reversals.

I am not asking for help debugging the electrical issue, which would be most welcome though I do have a few ideas to fix it, however I would like to know what state the OpenMV board is in. If the peripherals are working then what is the CPU doing?

The symptoms are redolent of an exception handler being entered however I cannot think of what exception could be thrown and how to verify this.

Let me know if any other information is required

Thanks
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iabdalkader
Posts: 630
Joined: Sun May 24, 2015 3:53 pm

Re: OpenMV power supply issue

Postby iabdalkader » Sun Feb 18, 2018 10:33 am

Sounds like a brownout, maybe adding two large caps on the input would help. I wouldn't waste time figuring out what the CPU is doing, if the conditions are not met it will be in an unpredictable state.

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