TLC5940 - Two LEDs Stay On But Other Fourteen Work


I hooked up the SMT version of the TLC5940 (PWP) to the Diecimila. I ran the BasicUse program which works for fourteen pins, as they blink through the knight rider sequence successfully.

Yet, Pins 0 and 13 are constantly lit. They are unaffected by the program's sequence. Pin 13 is really bright and Pin 0 is dimly lit. The sequence essentially works with these two leds removed.

Any suggestions?

Thanks, Gary

I hooked up the SMT version

Just spotted that, so wiped my previous answer.

What SMT version? There is no SMT version with pin 1 as an output

Pin1 is ground on the PWM package and SCLK on the RHB package.

My apologies, OUT0 (pin 7) and OUT13 (pin20).

It's the surface mount tlc5940PWP package;

OK so I will rewrite my previous observations.

AS theses pins are not at the extreme ends of the shift register inside the chip it is not likely to be a problem with the software.

As the LEDs light up then there is likely to be a current path but you can't change them so it might be you have a short between pins. However, more likely is that the chip has two faulty channels.


Somehow the GSCLCK (Digital Out from Arduino) got hooked up to an LED instead of PIN 18 , thought I double checked this...