I use 5.6k resistors. I think what your seeing is a slow scope. On 4/4/2018 9:50 PM, yassyass wrote: > Wrote a python script using SMBus to write to a slave I2C device. The > slave is detectable with i2cdetect which results in the following output > > debian@beaglebone:~$ i2cdetect -y -r 2 > > 0 1 2 3 4 5 6 7 8 9 a b c d e f > > 00: -- -- -- -- -- -- -- -- -- -- -- -- -- > > 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 30: 30 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- > > 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 70: -- -- -- -- -- -- -- -- > > > The slave device would not respond to commands and upon inspecting it > with a scope the voltage signal is appearing lower than the high > threshold and has a very high time constant it seems. > > > The slave device has its own internal pull-up resistors of two 4.7k > resistors one on each of the buses to the 3V supply on the BBB. > > > The frequency of the bus is set to 400kHz on i2c-2. The BBB is being > powered by USB only. > > > The following images are of the SCL bus > > > <https://lh3.googleusercontent.com/-c69x_jIGOBE/WsWp1gQJoUI/AAAAAAAAJGE/Fpx8Z3TQFTkmRZPEFy8m-T-AZiGlHQSmgCLcBGAs/s1600/ADS00006.BMP> > > <https://lh3.googleusercontent.com/-z85y11G_va0/WsWqWQJJnZI/AAAAAAAAJGI/1HJ3zJlqODgKNwRoqBIrdnfJWLs-PH8rQCLcBGAs/s1600/ADS00007.BMP> > > Could the issue be that the pull up resistors are too high? Does the > BBB require more power via an external source? > > > > -- > 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] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/5f323c46-4809-4f8f-aeb8-cb390d3288c9%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/5f323c46-4809-4f8f-aeb8-cb390d3288c9%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit 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/de8a16a1-a9d0-87ae-a6fc-e2c57c1ed3ed%40gmail.com. For more options, visit https://groups.google.com/d/optout.
