Yeah, I agree there is something else going on here. with a 1K resistor, the signals should not have a slow rising time. The rise time doesn’t look like a capacitor, but I agree, that is about the only explanation that would cause the rise time to slow like this. Maybe the I2C part is faulty. Try plugging in another I2C part to see if the problem persists.
Regards, John > On Apr 5, 2018, at 8:02 AM, Graham <[email protected]> wrote: > > > It looks like you have some extra capacitance on the bus. There should not > be any capacitors bridging the I2C data and clock lines. Some of the > third-party universal interface cards have extra capacitance, so take those > off. > > I have never heard of an I2C part with built in pull-up resistors. > > Do to the multi-drop nature of the I2C bus, pull up resistors are almost > always external. There are some "weak pull up" resistors you could turn on in > the BBB, but are too high in value for most applications. > > I suggest you read up on how to select pull up resistors for an I2C bus. > Phillips (now NXP) initially developed the bus and has good documentation. > Google: NXP I2C bus documentation > > But the short answer is that for a 3.3V bus, resistors in the range of 1.2K > to 3.3K should work fine. The value is not critical. You want to pull 1 to 3 > mA through the resistor when the bus is low. > > --- Graham > > == > > > > > > > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/a8ed3ca6-d286-4d29-8dc1-8851aa384db3%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/a8ed3ca6-d286-4d29-8dc1-8851aa384db3%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CA2B23DC-7B39-4E85-AB6E-2D196A6DE203%40gmail.com. For more options, visit https://groups.google.com/d/optout.
