trouble connecting a tlc5940

Other Hardware LEDs and Multiplexing
1

Hi everyone,
I have been trying to hook up a TLC5940 to an Arduino UNO (rev3). I have had some experience with ISP-ing to ATTiny85s and 2313s where everything worked fine but with the tlc5940 it does not seem to be working. I followed the instrutions according to Arduino Playground - TLC5940 and did the following:

  • Downloaded the Library and unzipped the Tlc5940 folder to /hardware/libraries/
  • left the board to "Arduino Uno" which might be my mistake, I couldn't find an ISP entry for the 5940 under "boards"
  • Connected the tlc5940 according to the wiring diagram (see below)

tried uploading various examples from "File>Examples>tlc5940", with an LED connected to the breadboard (long leg to power, short leg to output). The examples uploaded fine i.e. no error message but none of the output pins light up

------------ ---u----
ARDUINO 13|-> SCLK (pin 25) OUT1 |1 28| OUT channel 0
12| OUT2 |2 27|-> GND (VPRG)
11|-> SIN (pin 26) OUT3 |3 26|-> SIN (pin 11)
10|-> BLANK (pin 23) OUT4 |4 25|-> SCLK (pin 13)
9|-> XLAT (pin 24) . |5 24|-> XLAT (pin 9)
8| . |6 23|-> BLANK (pin 10)
7| . |7 22|-> GND
6| . |8 21|-> VCC (+5V)
5| . |9 20|-> 2K Resistor -> GND
4| . |10 19|-> +5V (DCPRG)
3|-> GSCLK (pin 18) . |11 18|-> GSCLK (pin 3)
2| . |12 17|-> SOUT
1| . |13 16|-> XERR
0| OUT14|14 15| OUT channel 15

Does anyone have an idea as to what I may be doing wrong? I am assuming that the code is being sent to the arduino and not the 5940 (which would explain why there are no error msg), but I am at a loss as to how I should be doing it otherwise. Any suggestions would be greatly appreciated.

Thanks,
Opal_1970

PS
I posted this in the LED forum but I am not sure if this should be a microcontroller topic please excuse me.

2

Ok, just for fun I removed the resistor from 5940 pin 20 to GND (connecting it directly)... with the effect that all the LEDs are flickering at different rates (if I understood the comments in the code correctly there is suposed to be a "Knight Rider" effect), but at least there is light... I will see what I can come up with, but in the meantime I would still appreciate any suggestions.

Thanks

3

Hi All,

ok, so far so good... I took the chip out and put it on a different place on the breadboard (also meaning re-doing the wiring). Now everything is working... so that means my breadboard has a problem or more likely I had the wiring wrong (I know what your thinking and you may be right, but I really checked and rechecked the wiring again and again).

oh well, important thing is that it is working, right? :slight_smile:

Thanks

4

important thing is that it is working, right?

No the important thing is that you learn that solderless bread board is crap and it causes more problems than it solves.

By making you unsure that what looks like good wiring is actually making a connection you are adding another thing that can be wrong. There are enough things in electronics that can be wrong without adding another.