I tried to get a PCA9685 to work at the moment I am using an Arduino with this library to test it but I can't get it to work. I have the Arduino Uno rv3 I wired the scl of the Arduino with the scl of the pca the same goes for the sda all the address pins are on the ground same goes for the ext clk and the oe.

Can someone see what I did wrong?

As requested more information: I connected the leds directly to the PCA9685 as shown in figure 15 from page 28 of the datasheet

At the moment the led always burns but with the example code from the library it should blink.

edit 2/8/2014 here is how i connected the arduino with the pca9685 enter image description here

I used the example program from the library but the leds don't change in brightness. (Just to make it clear i have 16 leds connected to the ports and not just one)

I hope its more clear now what I want. edit(2) 2/8/2014 Be course I have the uno r3 I use the 'special' sda and scl pins that are near the connector. (when i connect a led to these pins it blinks softly so there is a signal on the pins)

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    \$\begingroup\$ You don't use proper capitalization. That's wrong. \$\endgroup\$ Commented Feb 8, 2014 at 1:09
  • \$\begingroup\$ It is correct in English to capitalize "I" when referring to yourself. I have edited your question accordingly. Please try to observe proper punctuation and capitalization rules, otherwise you give others the impression that you don't really care about getting your question answered. \$\endgroup\$
    – JYelton
    Commented Feb 8, 2014 at 1:11
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    \$\begingroup\$ English nit-picking aside, your question lacks a schematic and detail about "what doesn't work." What would you consider to be "working" in this context? A blinking LED? Something else? What is a PCA9685? Now I have to go look it up. Such omissions are hazardous to the health of your question. \$\endgroup\$
    – JYelton
    Commented Feb 8, 2014 at 1:13
  • \$\begingroup\$ I don't have a schematic at hand now but if it is necessary i will drawn one tomorrow morning \$\endgroup\$ Commented Feb 8, 2014 at 1:24
  • \$\begingroup\$ Just to make sure, what pins are you using on the Arduino for SDA and SCL? \$\endgroup\$
    – user28726
    Commented Feb 8, 2014 at 21:53

1 Answer 1


Are the SDA & SCL line pulled up in the board? Apparently its not there in your circuit diagram. Connect a 10K from each of the two to +5v


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