PCA9506 not acknowledge

[Benkg]

I’m using the PCA9506 port expander. Power and ground are hooked up correctly. All address pins are pulled high - thus the 7bit address should be 0b0100111+R/!W. I am using a clock speed of 100kHz. I’ve scoped the signal and the first byte looks correct but there is no acknowledge from the chip and I can’t proceed from here. Am I missing something? Is my address incorrect? Or do I need to hold the !reset or !OE pins in a certain state during this frame? Thank you! 

[reyes · Accepted solution]

Hi,

Address is correct.

PCA9506 is compatible with I2C-bus standard mode (100 kHz).

!OE pin should be LOW for normal operation and !RESET pin should be HIGH for normal operation. Timing requirements for these pins can be found in Table 11 of the datasheet: https://www.nxp.com/docs/en/data-sheet/PCA9505_9506.pdf

Please performed a swap test (changing the ‘failing’ PCA9506 for a new device), just to make sure the problem is not the device itself.

Regards,

Jose

[Benkg]

Thank you, I don’t think I was driving the enable and reset pins correctly. I will try this and swap if it doesn’t work. Thanks Jose!