A library described below uses bit banging technique to connect serial SPI RAM to any free MCU pins thus keeping SPI slave interface free for other purposes. In our example we use 256K memory 23A256/23K256 from MICROCHIP. A different type with the same protocol or different capacity can be used too.
SPI is normally a four-wire serial bus. When connecting a serial RAM to MCU we can use only one MCU pin for both SO and SI so only 3 pins MCU are needed.
Code (in attachment) shows both the library and an example code.
Post sent by Hynek Syrovátka.