Dangerous Prototypes

Dangerous Prototypes => Bus Pirate Support => Topic started by: timb on May 27, 2013, 05:24:23 am

Title: Back feeding power pins for voltage monitoring?
Post by: timb on May 27, 2013, 05:24:23 am
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!
Title: Re: Back feeding power pins for voltage monitoring?
Post by: timb on June 01, 2013, 02:33:26 am
Hrmm, nobody? Someone has to know. :(
Title: Re: Back feeding power pins for voltage monitoring?
Post by: Sjaak on June 03, 2013, 09:17:17 am
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 :)