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Author Topic: strange voltage on SCL and SDA pins  (Read 2342 times)

prishvin

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strange voltage on SCL and SDA pins
« on: July 25, 2015, 01:57:36 PM »
Dear friends,
 
consider PINGUINO OTG, PIC32MX440F256H mcu, Supply voltage is 3.3V,
consider following pins:
SCL1/IC3/PMCS2/PMA15/INT3/RD10
U1CTS/SDA1/IC2/INT2/RD9
 
when the I2C module is disabled and TRIS is set to OUTPUT for those two pins,
driving them high, results in 1.75V at output.
 
Why the output is 1.75V?
 
Thanks!

kyrk.5

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Re: strange voltage on SCL and SDA pins
« Reply #1 on: July 27, 2015, 01:02:08 PM »
Hello,

i think I have the same board as you. Actually I never tried to use that pins as digital pins, since i needed the i2c functionality. Normally such strange things happen when the PIN is configured wrong. So first suggestion is to check if every other peripheral on the given pin is disabled. Usually PICs like to have strange config settings for Analog pins, and PWM. In my projects I have some code that disables this, so mostly I dont get such type of problems.

Both of the pins are showing the same symptom?

Later the day (or maybe later on this week) I can look on my board if the pins are working. But i will bet this will be a configuration issue.

JohnS

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Re: strange voltage on SCL and SDA pins
« Reply #2 on: July 27, 2015, 06:10:26 PM »
Maybe the 33ohm resistors?

With the pins they connect to?

John