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Topic: TLC5940NT and LEDs (Read 319 times) previous topic - next topic

neilinpa

I am using the standard TLC5940 library by Paul Stoffregen version 0.15.0 and Arduino 1.8.9 with a TLC5940NT chip.
When I use the example and follow the basicUse sketch, It compiles and uploads without issue.  However, when the code hits TLC.init()  all LEDs come on and stay on.  It does not matter what else is done in script. I also added aSerial print statements throughout.  It reaches all serial print commands, cycles through channels, etc, but no change on LEDs. All bright and always on after hitting the first Tlc.init().  I also tried different values in the init, no go,  always bright, always on.  Any help would be appreciated?  Do I have to do something else to the chip first?  Is it factory burned with some default?  At wits end, tried 2 chips as well. 

septillion

#1
Jul 17, 2019, 05:10 pm Last Edit: Jul 17, 2019, 05:10 pm by septillion
I would be far more concerned about how you wired it than code. Especially when you try to run an example. Leaves us to a schematic and (not or) photo's of the setup :)
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

neilinpa

Not sure what you meant by use fricking code tags. The section about adding to forums, states to use meaningful subject lines. Sorry.  Anyway, I had double-checked the wiring several times and decided to check again. Turns out, I was actually missing GND to the chip. I think what I learned so far, is use a standard for wires, wire grounds first, use different colors for certain functions. (red=vcc, blk=gnd)  or whatever standard and follow it. What is interesting is the chip was actually doing things without ground.   I think one of my reasons for asking about the chip itself and if there is some sort of default, is it does have an EEPROM and I just wasn't sure if there are different chips out there that need some sort of initial programming first.  In line, for example, ATMEGA328 chips can have all kinds of different boot loaders or none at all, so I was curious if the TLC5940NT also comes with different configs that require special attention before the library I was using would work. I realize wiring fixed my issue, but didn't really answer if in fact there are different chip/configs to be mindful of for the future.

septillion

Not sure what you meant by use fricking code tags.
For that, see "How to use the forum". But do note it wasn't part of the message to you but simply my footer :)

Anyway, I had double-checked the wiring several times and decided to check again. Turns out, I was actually missing GND to the chip.
Check, double check, triple check. Someone from Czechia you call a c(h)eck. If it still doesn't work, leave it for an hour and check again :D

What is interesting is the chip was actually doing things without ground.
Driving a chip without power (GND or Vcc) can cause strange things. See Phantom power.

I think one of my reasons for asking about the chip itself and if there is some sort of default, is it does have an EEPROM and I just wasn't sure if there are different chips out there that need some sort of initial programming first.
If that was the case you would be able to find that in the datasheet. And probably also in the documentation of the library for that chip. But in this case you should at least have some control over the leds.

In line, for example, ATMEGA328 chips can have all kinds of different boot loaders or none at all,
That's even the default to come blank unless otherwise stated :) But now we are talking micro controller which task it is to do nothing it isn't told :)

PS Some paragraphs would have made your text easier to read. Took some time to extract all the pieces of info. No hard feelings thou :)
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

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