From: Dave H. <dhy...@gm...> - 2006-11-10 22:08:20
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Hi Chris, > I'm new to a lot of this, so it's possible I did something wrong. I > connected the black lead on the multimeter to MOTOR ground, and the red lead > to the pin in question. That's correct. You need to be careful that your probe is only touching one pin, but based on your readings that seems to be the case. > Is there something wrong with the voltage regulator? > Why am I seeing the correct voltage for the SCL pullup and not for anything > else? There is definitely something fishy going on. I'm also suspecting more than one problem. I see I forgot the link to the photo: http://davehylands.com/gumstix-wiki/i2c/Robostix-SCL.jpg (but obviously you found it) Some additional places to check: 1 - Right next to the "Pin 7" is Pin 8 (on the 9515). It should have 3.3v on it. 2 - Following the fat trace coming off of pin 8 and heading left is a 5 pin voltage regulator. Pin 5 (top left as seen in the photo) is the output from the 3.3v voltage regualtor. It should be 3.3v. 3 - Pins 1 and 3 of the 3.3v voltage regulator (bottom left and bottom right) should be at around 5v (the same as the power jack). There are 3 other voltage regulators on the board. Each is an 8-pin 5219. U$59 is to the left of the ATMega128. U$60 is the upper one closest to the ATMega128 on the right hand side and U$50 is the one below and to the right of U$60. Each of these chips has a little dot in one corner. This indicates pin 1, and pins 1 thru 4 are on the same side of the chip. When the gumstix is not plugged in, then Pin 1 (enable) of all of them should be around 3.3v (actualy U$50 pin 1 should be around 5v). Pin 3 (output) of all of them should be at 5v. If the enables are low, then the outputs won't be at 5v. The enables of U$59 and U$60 are pulled up to 3.3v by the U$62 resistor pack (close to the hirose connector). If for some reason the 3.3v regulator isn't working, then that might explain some things. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |