ATTiny85 and the TI-TLC5973

Go To Last Post
5 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Greetings all, I am working on a simple circuit design to have something to practice coding PMW LED effects in the ATTiny85 for the TI-TLC5973.  I have 3 5973's cascaded together, but was curious if there was any benefit to connecting the last SDO back to the 85.

 

Also, 10k is the right resistor value for the pullup on the button input, right?  I could remember for certain if it was 10k or 1k.

Attachment(s): 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Welcome to AVRFreaks.

 

I have no experience with the 5973. However, I cannot see any benefit in looping the serial  data out pin back to the T85.

 

"button input", "pullup"  If you are referring to your schematic's S1 Toggle switch, your R7 (10K) is actually a pull DOWN resistor. It is a more common practice to have the switch in the ground side of the diagram and R7 pulling the input pin UP to the Vcc line. But there is no crime committed if you do it your way. Just  call it a pulldown resistor to avoid any confusion for all readers of your subsequent documentation. cheeky As for the value, I usually use 10K but there is nothing religious about the actual value; 47K would be OK also. I would probably not use 1K myself because of the 5mA drawn from a 5volt rail during the switch action.

Ross McKenzie ValuSoft Melbourne Australia

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I'd suggest adding some bypass capacitors to the power rail.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Precisely the input I was looking for.  Thanks!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The only reason I can think of to loop back the SDO line is to use the LED drivers as memory. You can then rotate through the entire string and just change the LEDs that need updating.

No practical use with just 3 drivers, but in some instances could allow you to exceed the RAM limitation of the '85 (~170 pixels).