by Guest » Sat Feb 26, 2005 7:01 pm
Ok...I just ran a few tests with a board that is essentially at the same assembly point that yours is at (i.e., I removed all the ICs, and removed the camera).
The circuit seems to draw around 4.5 mA with just the green LED on (this current is measured at the Vin polarized terminal). 0.8 mA doesn't seem right, as I would think the LEDs would be drawing more than this.
Pins 5 and 6 on the mega8 should be connected, and connect to pin 14 on the camera, but this should definitely not be connected to ground. I just checked a dozen blank v1.2 PCBs to see if any of them had a short between pin 5 on the mega8 and ground, and none of them did. This is interesting though...a short between pin 5 and ground would explain a problem another user was having, where any command requiring the detection of a transition on pin5/6 never seemed to happen (i.e., if the lines were shorted to ground, no transition would ever occur). Anyway...
A voltage of 4.5 volts at pin 12 is, again, strange. Lets see...something is dropping 0.5 volts someplace...I'm not sure what that could be though.
Another item to note is that the output of pin 12 also goes to the three-pin header along the left side of the board. SIG1 labelled on the board is directly connected to pin 12 of the mega8. The thinking here is that the user could drive some external device with this line if they wanted to. Check around this header to see if anything looks fishy.
Also, the 500 ohms between pin 12 and Vcc...two 1K resistors in parallel would give this resistance...there are several 1K resistors in the circuit, one of which should go from pin 12 to the yellow diode...but this doesn't really explain how you could get the 500 ohms...
Can you measure the resistance between pin 12 of the mega8 and the anode of the yellow LED? This should read 1K...
I'll keep thinking about what could be going on here...post back if you find anything else out.