PCA9955B Led driver with Raspberry pi 4b

mahaboob — Thu, 19 Sep 2024 06:07:22 GMT

Hi,

PCA9955B Led driver I2C connected to Raspberry pi 4b, here Led driver address shows 70, 76, 3f.

but we selected address 15: AD0-GNDD,AD1-VDD,AD2-GNDD so this address not shown.

after that we connected two Led drivers one is address 15 and address 05: AD0-VDD,AD1-GNDD,AD2-GNDD.

in raspberry pi 4b putty terminal we detect I2C address but it shows only 70, 76, and 3f.

1. Why does the I2C scan show addresses 70, 76, and 3f, instead of the expected 15 and 05 for the PCA9955B LED drivers?

2. Both Led driver connected in the circuit, in the software code i select 1st Led driver to turn ON Leds but here both Led drivers are working parallelly ?

please tell me how to solve this issues.

Re: PCA9955B Led driver with Raspberry pi 4b

TomasVaverka — Thu, 19 Sep 2024 07:53:48 GMT

Hello Mahaboob,

I have not heard of such an issue before and there is no errata document for this LED driver.

In order to better understand what is causing the behavior you are observing, could you please share your complete schematic?

If you have a logic analyzer or an oscilloscope, can you also share:

1. The I2C traffic when using your selected 7-bit slave addresses of 0x15 (= 8-bit write address 0x2A) and 0x05 (= 8-bit write address 0x0A)?

2. The power-up sequence with VDD, AD0 - ADD2 pins?

BRs, Tomas

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PCA9955B Led driver with Raspberry pi 4b

Re: PCA9955B Led driver with Raspberry pi 4b