LCD TFT Controller (LTDC) frame rate .

[zeros_and_ones1991]

Posted on December 11, 2014 at 13:09

Hullo guys , I was wondering about the frame rate of the LTDC in STM32F4xx series , There is no obvious information in the user manual about the frame rate , and in the demo example , I just set the pixel value in the SDRAM buffer and then it's supposed to be displayed without touching the LTDC module after turning it on , as if it starts displays the new data as soon as it finishes the previous frame . if this how it works , wont that consume the AHB bus , and thus prevent the processor and other peripherals from working ? 

Any clearer documentation will be good for this part Thx in Advance .

[Tesla DeLorean]

Posted on December 11, 2014 at 20:24

Wouldn't the pixel clock and display dimensions tend to define the frame rate?

Yes, I would expect is does a DMA memory loop painting each raster of each frame, with the aid of fifo and burst buffers, and a bus matrix configuration to prevent it saturating the AHB bus. Accessing the same resources at the same time will cause some contention, and delay the lower priority device.

[zeros_and_ones1991]

Posted on December 11, 2014 at 23:11

Thx a lot Clive , by frame rate , I meant the time interval between frames (which is not there obviously) , not the time of displaying single frame (as this time is small compared to the time between successive frames in the normal case ) .

The LTDC does not need using one of the DMAs , so as u know u just point to the buffer of the Layer , then it works continuously . I guess u r right regarding the bus usage (because that was the reason for my confusion) , but would the  FIFO  (which would be 4 word deep) be enough not to saturate the bus ? If it really works that way , that means the CPU and other Processing will really be VERY SLOW , when the LTDC is on . That's really confusing .