Content originally posted in LPCWare by rgledhill on Tue Apr 29 10:43:22 MST 2014
Make sure there are pull-ups on the SCL and SDA lines - there may be some on the LPC1769 board already, I'm not sure, but check as they will be required. Then check your I2C Baud rate; some devices talk at 400kHz, some at only 100kHz. I'd look at the trace lines on an oscilloscope and check the waveforms look clean (straight edges everywhere). When debugging the software, check to see if it receives a NAK, which would mean that the remote device is ignoring the data.
Hope this helps as a start!
Richard