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Manage constrained resources

This application note discusses the options available to manage constrained resources when using an e-paper display.

SRAM

The frame-buffer needed for preparing and keeping the images resides in the internal SRAM of the MCU. The sizes for each panel are listed in this table.

If the internal SRAM of the MCU is too limited, an external SPI SRAM can be used.

The application note provides the procedure to Use external SPI SRAM for frame-buffer.

Note that the external SPI SRAM is slower than the internal SRAM.

Flash

The fonts are stored in the internal Flash of the MCU.

If the internal Flash of the MCU is too limited, an external SPI Flash can be used.

The application note provides the procedure to Use external SPI Flash for fonts.

GPIOs

Driving an e-paper display through the EXT3 expansion board requires a minimum of 8 signals, and up to 16 signals with touch and external memory.

Signal Minimal Touch Optional
Power +3.3V, Ground
SPI bus Clock, Data in Data out
Panel Select, Reset, Busy, Data/Command Second select
Flash Select, Second select
I²C bus Clock, Data
Touch Reset, Interrupt
Total 8 4 4

The application note provides the procedure to Use GPIO expander.