I am trying to control an Analog Devices programming resistor AD5254 by a USB to I2C master device from MicroChip MCP2221. The problem I am facing is that each time MCP2221 is waiting for ACK from AD5254, the SCL clock de-assert which i think affect the AD5254 to not be configured properly. This is what happens : 1. Using MicroChip I2C/SMbus Terminal I am sending the following : 2. observing SDA/SCL using a scope + I2C protocol analyzer I can see the address+data are ok but after each Ack SCL line drops : 3. I know that the address+data is correct because I am using Analog Devices Evaluation board for reference, and when connecting their SDP-B controller board (UG-277) to the Evaluation (UG-236) the SDA/SCL signals are correct :
Anyone know why SCL drops after each ACK ?