LPC43xx USB1 causing glitches on LCD

[gustavvaleur]

Hi we are experiencing some graphical glitches on a LCD connected to a LPC4357 when we are transferring data on USB1.

We have seen a similar issue with USB0 that was resolved by setting SBUSCFG to 7.

is there a similar fix for USB1 as the reference manual does not seem to mention a SBUSCFG register for USB1?

[gustavvaleur]

Hi Carlos

Thank you for the help the problem was the LCD FIFO not getting filled up in time we have solved it by reducing the refresh rate on the display, as the other ideas you gave are already implemented.

[Carlos_Mendoza]

Hi Gustav,

It is good to hear you have solved the problem.

Best Regards!
Carlos Mendoza
Technical Support Engineer

[Carlos_Mendoza · Accepted solution]

Hi Gustav,

I assume the USB DMA also uses the SDRAM? This glitches could be a result of LCD DMA unable to service the LCD FIFO in time, you could use the FIFO Underflow to monitor for this. As a workaround you could slow down frame refresh rate and pixel clock if possible, use 32-bit wide external memories, increase the SDRAM clock speed, use faster SRAM, profile code and move time critical code to internal SRAM.

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer