This is a simple application which maps two external memories and a display to an STM32F7 chip's internal memory space. I wanted to learn how to use external memories with STM32s, and I was pleasantly surprised by how easy their memory-mapping peripherals are to use.
The target hardware is an STM32F723IE Discovery Kit:
https://www.st.com/en/evaluation-tools/32f723ediscovery.html
These boards have a traditional 8-pin Flash chip which the QSPI peripheral maps to 0x90000000, and a parallel PSRAM chip which the FMC "Flexible Memory Controller" peripheral maps to 0x60000000.
This example runs a couple of memory read/writes on the external RAM and Flash, and prints the results over the debugger's USART serial connection at 115200 baud.
There's also a 240x240-pixel TFT display connected to "bank 2" of the FMC peripheral, but since its interface only supports "data" wires, its registers and display memory are accessed through two pointers. 0x64000000 is the "data" address, and 0x64000002 is the "command" address. In practice, it works about the same as a SPI TFT display; the signals just use a parallel interface instead of a serial one.
This example uses "memory-to-memory" DMA to quickly send data from the external RAM to the external display. Each frame, it clears the framebuffer to a new color and prints a message including the current framerate.
It also enables an interrupt connected to the TFT's "tearing effect" pin and includes commented-out code which synchronizes data transfers to the display's "vblank" period. But the example runs ~8fps slower if it waits for the "vblank" interrupt to trigger new DMA transfers, and I didn't notice any tearing or artefacts when I ignored it.
I'm sure there are a few ways to speed things up, but even with the entire framebuffer and display getting refreshed every frame, I get a reasonable framerate of 27-30fps using this approach.