Software

Software SPI

The Software SPI protocol (SW SPI), also known as Bit-banging, is slower than the Hardware SPI protocol (HW SPI) but offers flexibility by allowing any available pins to be used, while still providing sufficient speed for most graphic applications.

A refresh takes anywhere from a few hundred milliseconds to several seconds, depending on panel size, temperature, and update mode — this dwarfs any SPI transfer time by orders of magnitude.
Crucially, once the data has been sent and the refresh command issued, the EPD controller drives the rest of the update internally and does not need the SPI bus again until BUSY clears.
This is unlike a TFT, which is written to continuously and needs the bus available on demand — so sharing the SPI line with other peripherals is generally safe with an EPD in a way it isn't with a TFT.

As with any shared SPI bus, each device still needs its own chip-select line, and your code must not attempt to issue further commands to the EPD until BUSY clears (handled automatically by this library — see "Communicating With the Controller").

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