I'm having issues with a TLC5946.
What I originally did, is
- SCLK, SIN, XLAT, MODE and XHALF connected to MCU
- GSCLK connected to independent oscillator (30MHz)
- BLANK not used / set to 0
So, what I expected, is that the PWMs would run independently and continuously after having been set up once. I expected that after initialization no serial communication and no manual BLANK pulses would be required for continuous PWM display until I want to change greyscale LED data.
But the result looks like this is not the case and in the datasheet there is no definite answer:
When being used as described above, nothing is being output at all. Only after sending a positive pulse on BLANK, the LEDs are lit once - but not continuously! I did also try to send the XLAT pulse only inside a BLANK pulse, but the result is the same.
It very much looks like a manual BLANK pulse is required after each PWM cycle. But is this really the case? I cannot believe that the PWM counters do not autorefresh, because this would absolutely not be desireable and would create constant CPU load to generate these continuous BLANK pulses. And since they would have to be in sync with the GSCLK, even that might have to be generated manually. This would render the device nearly unusable with a MCU only.
Someone on the forum has experienced the same behaviour here, but his description was misunderstood and therefore the answer missed the point.
So, my actual questions are:
- Do the PWM counters run independently and continuously after initialization or do they require to be refreshed by a BLANK pulse after each cycle manually?
- If the latter is the case, how is it intended to use these devices with an MCU only? How to generate thes BLANKs and GSCLKs efficiently then?
- If the latter is the case, is there any alternative in the TLC594x family on which the PWM counters do run independently for standalone use? (pin compatible preferred)
- If the first is the case, what can be the reason that they do not run independently in my case?
Any thoughts are very much appreciated. Thank you!
Stephan
