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Topic: Back feeding power pins for voltage monitoring? (Read 1073 times) previous topic - next topic

Back feeding power pins for voltage monitoring?

Right now I'm using my Bus Pirate to sniff some I2C traffic between my Raspberry Pi and a circuit I'm working on. I've got the RPi providing 3v3 and 5v to the circuit in question. I noticed, quite by accident, that leaving the Bus Pirate's 3v3 rail hooked in would cause the VREG LED to light up. Hitting "v" to see the voltage status I was able to read the voltage coming from the RPi.

It occurs to me that being able to use the BP's 3v3 and 5v outputs as inputs could be rather handy for monitoring an external circuit's voltage rails, especially on something as power finicky as the RPi. Is it safe to do this? (Assuming I keep the BP's VREG off, of course.)

Thanks!

Re: Back feeding power pins for voltage monitoring?

Reply #1
Hrmm, nobody? Someone has to know. :(

 

Re: Back feeding power pins for voltage monitoring?

Reply #2
AFAIK are the voltage regulator in HiZ when powered off/disabled so I guess it isn't a big deal.

From personal experience the Buspirate (and microchip uC) is very forgivenable to abuse :)