I2C Problem Maybe Fried

I've been connecting sensors to the i2c line on the apm 2.5 and after a little while the i2c port stops working. This is the second APM this has happened to and I can't keep on spending money. 

Here is what I did to trouble shoot. I uploaded the arducopter firmware onto the apm 2.5 and try to connect to mission planner, but it gives me an error that says no packets received. Then I pull up the arduino serial monitor. The first two errors that show up are that the barometer and compass can't be initialized and calibrated respectively. 

I just checked the voltage out of the I2C port and it is 228mV, which is really low from the correct 3.3V that the I2C voltage should be at. 

I need help soon! This control board is part of my thesis project and the copter needed to be flying yesterday!

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  • 3.3V Regulator Issue

    Hope this helps.


  • did you ever find a better 3.3v regulator and replace it? I think this is my problem also as I have 0.2v coming from the i2c port and 1.8v coming from the PM port next door. Thinking its shot… what you think.

  • Admin


    There is a 3.3vdc regulator on the APM2.5 pwb that supplies the I2C port and other ICs that require 3.3vdcand it probably dead.


    TCIII ArduRover2 Developer

  • Do you have an oscilloscope? It's pretty hard to tell what's going on on the I2C bus with just a tester.

    I2C can be really hairy, I'm surprised it works as well as it does.

    Can you detect a certain sequence of events? Devices have addresses, Is it always the same thing that you connect that causes problems (conflict of address), or does everything work for a time, and then quit after a time? How many I2C devices do you have connected?

    Do you change anything around the time that the I2C stops? 

    It would be strange that more than one APM fries(that it is an APM problem). It would seem that there woud be a lot more people complaining.

    I2C has 2 speeds, Timing is important. Do you have anything new or in development on the bus? Bus wire length can be imporant, interference, that kind of thing.

    Just throwing some stuff out there. In development I've had my challenges with I2C. Once it's clean it's usually quite stable though.

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