2014-06-15 04:45 AM
Hi,
I am trying to control a TFT over LVDS with an STM32F429. At around 30 MHz the Signal seems to be ok, but the Display wants at least 40MHz. Turning up the Speed above ~33Mhz is messing up the clock signal and visible errors occur. The datasheet says it should work with up to 42MHz. Is there a chance to get a clean 42Mhz signal by following some Layout rules or adding some components (until now i added a resistor and a capacitor, that got me up to 33Mhz) or should i switch to another controller?2014-06-15 05:00 AM
GPIO have settings to control output speed (slope rate control), did you take care to set all fast lines to support at least 50MHz.
-- laurent2014-06-15 05:23 AM
yep everything set to max
2014-06-15 05:33 AM
What about compensation cell setting ?
2014-06-15 06:38 AM
i didn't know it existed, i will read some more about it, thank you!
2014-06-15 08:07 AM
How are you viewing the signal? If you are using a 1X/10X scope probe, make sure it's in 10X mode
2014-06-18 03:27 AM
The probe is on 10x. Activating cell compensation did not help. I built an adapter for the 429 Discovery board to check if my own STM32 Board had major flaws before the LVDS part, but the result was the same - output is fine until ~33MHz and then gets worse the higher you go ( starts with image jumping, total running mess @40MHz ).
2014-06-18 07:39 AM
turns out that the limiting factor is the external sdram. will post if i find anything interesting.