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jflemer-ndp / libmpsse

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I2C Read gives one bad bit, but only rarely #47

Open GoogleCodeExporter opened 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?

1. Using an FTDI C232HM-DDHSL-0, USB to MPSSE cable connecting Linux server to 
I2C/SMBus/PMBus power supply
2. Repeating many times, command the power supply to provide a data value
3. Read a known 16 bit data value from the power supply
4. Observe the I2C traffic with a scope

What is the expected output? What do you see instead?

We expect 0xC6 0x00, and get it about 99% of the time. About 1% of the time the 
we see 0xC6 0x02 or 0xC6 0x08. And extra bit, always only one extra bit, is set 
in the byte that should be 0x00. When we look at the data with the scope, the 
bad values appear to be good clean representations of 0x00.

What version of the product are you using? On what operating system?

libmpsse 1.3, using the C interface, CentOS 6.4. 

Please provide any additional information below.

There're obviously many ways this could be a system problem having nothing to 
do with libmpsse. But I wonder if anyone has seen something similar.

thanks, Michael

Original issue reported on code.google.com by 2541bwtl...@gmail.com on 6 Jun 2014 at 6:11