Is it safe to leave stuff connected to the GPIO pins when the Pi is powered off?

Question

I am asking about stuff that would be within the normal operating limits when the Pi is on, i.e. 3v3 level voltages at small currents, when the pi is shut down (but still powered), and also when the Pi's power has been completely removed (and thus it's ground would be floating relative to the input signals)

specific case: it seems like the l293d (or sn754410 alternative) motor chip tends to "leak" small amounts of current when powered on - do I need to completely disconnect it from the Pi when I want to shutdown the Pi?

(yes, one solution would be to power it from the pi such that it shuts itself down when the pi power is removed, but I am curious what would happen and if it's safe)

Answer 1

When the pi is at halt but still powered you're fine. With no power to the pi, I would recommend making sure that there is no power leaking into the GPIO. It probably won't toast things, but the GPIO do connect directly to the Broadcom SoC with no buffering. So there is a chance of breakage.