STM32H750 USB3300 USB HOST with LCD interface does not work properly

[JeffreyNie]

Hello everyone, I encountered a problem while using the STM32H750 MCU.

 

The hardware environment is STM32H750 + USB3300, which is used as a USB HOST HS to collect camera data.

An LTDC interface is used to connect a TFT-LCD for display.

An external SDRAM of 32MB is expanded, with a bus width of 16 bits.

 

Currently, when both the camera data and the LCD frame buffer are in the internal RAM, the MCU works normally. However, when the LCD frame buffer is placed in the external SDRAM, the USB HOST fails to work properly.

[FBL]

Hi @JeffreyNie 

USB Host HS requires timely and low-latency access to USB. Since, external SDRAM access latency is higher than internal SRAM, so,  heavy SDRAM usage by LTDC may cause bus contention or delay servicing USB interrupt, leading to USB failures.

I suggest handling camera data in internal SRAM. So you can place USB Host DMA buffers exclusively in internal SRAM and keep display frame buffer to external SDRAM.