Control WVGA display with stm32f429-discovery LTDC

Question

I am trying to output some data on the 7 inch TFT-LCD display (MCT070PC12W800480LML) using LCD-TFT display controller (LTDC 18 bits) on STM32F4.

LTDC interface setting are configured in CubeMx. In the program lcd data buffer is created with some values and it's starting address is mapped to the LTDC frame buffer start address.

At this moment display doesn't react to data sent by the LTDC. It only shows white and black strips, after i connect ground and power for digital circuit to the 3 volts source. VLED+ is connected to the 9 volts source. The VSYNC, HSYNC and CLOCK signals are generated by the LTDC and they match with specified values. I measured them on LCD strip, so the connection should be right. I also tried putting pulse on the LCD reset pin, but that doesn't make any sense.

The timing setting might be wrong.

LTDC clock is 33 MHz.

Here is the link to the diplay datasheet http://www.farnell.com/datasheets/2151568.pdf?_ga=2.128714188.1569403307.1506674811-10787525.1500902348 I saw some other WVGA displays using the same timing for synchronization signals, so i assume that timings are standard for that kind of displays.

Maybe signal polarity is wrong or i am missing something else. The program i am using now, worked on stm32f429-discovery build in LCD i just changed the timings. Any suggestions?

Thank you.

Answer 1

It could be something else, but I can see a problem with your timing values.

The back porch for both horizontal and vertical includes the sync pulses, but there must be a sync pulse width. My observation is that you have tried to get the total clocks for h = 1056 and v = 525 as per the data sheet by setting the sync pulses to 0. That won't work.

I would make the hsync pulse 20 and vysnc 10. The total clocks will be the same, but it is not critical that they match the spec sheet.