lpc1769 sporadical i2c problems

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by SplasH on Thu May 08 03:12:47 MST 2014

I have some sporadic problems with my i2c communication. In some cases the lpc sends two write commands to my slave device, but only one is wanted. Interesting is, that it first sends the correct command and after that the same but the highest bit is also set. So a write command of 0x03 is followed by 0x83 and the command 0x3B follows a 0xBB.
I have two devices as slave and both have this problem. I also tried a new lpc and slave devices.

Attached you can find three screenshots of the captured traffic on the bus. The first two show the wrong write command directly after the slave address. The third shows the whole traffic over 100s and peaks where I can definitely say, that the communication had errors. The master communicates with the slaves periodical at 250Hz.

I checked the bytecounter in the send routine if it counts higher than one, but it never does.

Has anyone an idea what the problem could be and how I can fix it?