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Device Address for PCA9955

Question asked by Phil Ma on Mar 1, 2016
Latest reply on Nov 29, 2017 by Troy Reabe

Hey there,

 

I'm trying to set up the PCA9955 Led Driver with I2C. I set the four hardware selectable pins A0-A3 to ground (VSS), so that the device adress should be 110 0000 (C0h including R/W bit). Problem is, the driver doesn't send an acknowledge bit as a response (I connected the I2C to an oscilloscope).

By addressing it with the ALLCALLADR (E0h) or SUBADDRESS (ECh) an acknowledge bit is set und the following messages can be transmitted.

 

As I got only one driver on the bus I could use this addresses to set up the driver, but as I read in the datasheet, this address is only for read transactions?

 

I can't get the issue of the addressing problem. The selected address shouldn't be a permitted one...

 

Hope someone can help.

 

Greeting,
Phil

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