Use external SPI SRAM for frame-buffer

The Commercial edition allows to use an external SPI SRAM as frame-buffer. The EXT3.1 extension board exposes pads for an SOIC-8 SPI memory, labelled U2.

The corresponding chip select pin differs according to the extension board.

EXT3EXT3.1EXT4

Variable	Number	Signal	Type	Function
.flashCSS	20	F_CS2	I	Second SPI memory chip select

Variable	Number	Signal	Type	Function
.flashCSS	11	F_CS2	I	Second SPI memory chip select

The cable of the second panel chip select signals does not have an assigned colour on the EXT3.1 extension board.

Variable	Number	Signal	Type	Function
.flashCSS	16	F_CS2	I	Second SPI memory chip select

Configure

• Open the configuration file hV_List_Options.h;

• Set SRAM_MODE to USE_EXTERNAL_SPI:

#define SRAM_MODE USE_EXTERNAL_SPI

• Ensure the chip select pin for the external SPI SRAM is defined for the main controller board:

const pins_t myBoard =
{
    // ...
    .flashCSS = 38, ///< EXT3 pin 20 Black2
    // ...
};

• Declare the screen with the model of the screen and the configuration of the main controller board connected to the EXT3.1 extension board.

Screen_EPD_EXT3_Fast myScreen(eScreen_EPD_271_PS_09,
    boardRaspberryPiPico_RP2040);

Caution

Do not specify a frame-buffer, as the library manages the external SPI SRAM internally.

• Clean the previous build and launch a new compilation.

Use

The screen with external SPI SRAM behaves the same as with internal MCU SRAM. It is only slower.

Example

The example for external SPI SRAM is identical to the example for internal MCU SRAM.