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?
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