TLC5973 EasySet - cant make it work...

Cristian Cesane

Other Parts Discussed in Thread: TLC5973

Hi guys,

I've spent two days trying to make this TLC5973 work, but, eventually, I let down my ego and thought ask some experienced guys about my problem. Here is the plain code...

uint32 write = 0x3AAFFFFF;
uint8 count = 48;

for(; count; count--)
{
  out(1);
  delay_cycles(1);
  out(0);

  if(bit_test(write, 31))      // if MSB is 1
  {
      out(1);
      delay_cycles(1);
      out(0);
  }
  else
  {
      delay_cycles(4);
  }
  
  write <<= 1;
}

I know that the last 16 bits are 0, but that's not the problem. I have a LEDs on all channels and at least one should be full bright, second should be dimmed, and the third should be off. Unfortunately, for some reason, all of them are off.

The period is 5us, and from oscope wave form I can't see any problem. From my understanding, if I'm letting the line down (0) for a longer period of time (at least 8 cycles), it should apply the new values, right? I'm posting the wave form here...

Thanks, in advance.

over 10 years ago

0 Rosley Ge over 10 years ago

TI__Intellectual 950 points

Hi,

I think your first part is OK from your waveform. But could you send a whole signal period to us and also how did you connect LED to the IC. We can help you based on these.

Thanks,

Rosley

0 Cristian Cesane over 10 years ago in reply to Rosley Ge

Prodigy 50 points

Hi Rosley,

The waveform is generated by the posted code. I'm starting with a 32bit value of 0x3AAFFFFF which has the start sequence followed by 20 bits of 1 and rest of zeroes. Of course, you need 48 bits in total, but the code snippet will just output 0s to the last 16 bits. I have LED to all three outputs, but I see nothing. I'll try getting an entire wave form, however, my scope is rather modest.

One other thing that may be interesting to mention, is that the SDO from chip is outputing the same signal if I'm sending these bits in a loop, even If I'm waiting more that 8 cycles between each iteration. The spikes from SDO are having a shorter period, which means, somehow, they are re-generated.

I'm posting the schematic here.

0 Cristian Cesane over 10 years ago in reply to Cristian Cesane

Prodigy 50 points

I'm attaching the full wave.

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TLC5973 EasySet - cant make it work...