STM32L4R9 Disc External PSRAM and octo SPI Flash

[Bing Wang]

I'm complete new for STM32L4R9 Disco. I found on the board, the PSRAM chip has two component marks U5 U6. But in its schematic, U5 and U6 are the independently chips. Also the OctoSPI flash on the board has two component marks U23 U24. Why?

Indiationally, I want to using ToughGFX and STM32L4R9 with AMOLED to design a smart watch with a cool ui interface. I'm not sure how much RAM and flash memory need to design a huawei GT like watch. I know the huawei GT watch has 16M RAM / 128M rom inside it.

Thanks for any response.

[Martin KJELDSEN]

I can't answer what you're asking in terms of components, but i can answer with respect to TouchGFX.

I don't why the GT watch has 16 MB of RAM - It's not like TouchGFX requires this by any means. I don't know how much space they're using for assets either ( -> external flash). Something that would require external RAM would be one or more large framebuffers, additional caching (canvas renderer, font caching, bitmap caching). You can calculate the size of your required external flash memory by summing up the size of the images (for that bitdepth) that you'll use along with font assets.

A good start is trying to do something in the simulator that you want to achieve and then building with your target toolchain, check the map file to see how much space is required. It's a matter of aligning budget with expectations. Expect high performance? Expect to pay more. Have little money? Set the bar lower for complexity of the UI.

/Martin