Thread: [HELP] Short-circuit fault detected when running flashlight
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Copernicus is offline Copernicus
2013-06-16 , 19:30
Posts: 1,986 | Thanked: 7,698 times | Joined on Dec 2010 @ Dayton, Ohio
#7
Originally Posted by Alecsandru View Post
the question is: it's really detecting a short-circuit? and if it detects the short-circuit , where is it? how do it get detected ?
Ah, I've been playing around with the flash LEDs recently, so I know a little bit about it. I'm not sure how many flashlight apps are out there right now, but I suspect all of them are using the "Video for Linux 2" (V4L2) interface. That interface allows you to query the hardware for a variety of error conditions, including timeouts, overvoltage, overtemperature, and short circuit.

From the ADP1653 data sheet, there is this info about the short circuit fault:

Short-Circuit Fault
The HPLED pin features short-circuit protection that disables the ADP1653 if it detects a short circuit to ground at the cathode of the LED(s). The ADP1653 monitors the HPLED voltage once the part is enabled in torch mode. If after 820 ms the HPLED pin remains grounded, a short circuit is detected. INT goes low, and Bit D3 (FLT_SCP) of the FAULT register is read back as high. Avoid false triggering of the Short Circuit Fault by not changing the torch current level while the short-circuit detection circuit is making a measurement of HPLED pin voltage. Do not change torch setting directly between two non-zero torch levels 750 ms to 900 ms after the torch has been enabled. To change torch mode current level between two non-zero torch levels 750 ms to 900 ms after enabling torch mode, use the following sequence:

Torch Current Setting #1
Torch Current Setting = 0
Torch Current Setting #2

Torch mode and flash modes can be enabled or disabled at any time.
It appears that this fault condition is specific towards the use of the LEDs in Torch mode, rather than Flash mode.

So far as I know, V4L2 only allows a single Torch current setting, so you shouldn't be able to cause a false trigger the way that they describe. However, I guess that would depend on how the app is connecting to the LEDs.

Quick question: when this error first crops up, do the LEDs come on for a brief period (half a second or so), or does the error message come up immediately?

EDIT: Ah, actually you've already answered that question in the first post. If it was a fault in how the software was accessing the LEDs, I would assume the error message would come up immediately. The fact that the LEDs stay on for a while may indicate that there is, in fact, a short circuit going on somewhere...
Last edited by Copernicus; 2013-06-16 at 19:34. Reason: Already answered
 

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