How to connect multiple SPI displays to a single controller/Arduino ? (connection diagram included)

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Connect multiple SPI displays to a single controller

SPI Definition:

The Serial Peripheral Interface (SPI) is a synchronous serial communication interface specification used for short-distance communication,
primarily in embedded systems. The interface was developed by Motorola in the mid-1980s.
It is widely known for small distance communication, maximum distance for SPI communication is limited to below 10m.
And the distortion in data is directly proportional to the distance.

Multiple SPI device connection Arduino multiple SPI SPI device connection with Arduino
SPI displays with Single Arduino

"If you want to connect N number of devices you only need 3+N number of pins"

Connecting multiple Display modules in Arduino is always sounds impossible , as it is limited by SPI pins .But the fact is it is as simple as connecting one single SPI device - yes!, If connecting single SPI device is easy for you then  connecting multiple SPI devices to a controller is just repeating the same work N times.

The figure below shows the generalized pin-out of SPI devices

SPI connection pin
All SPI devices will  be having these 4 pins , MOSI,MISO,CLK,CS

MOSI:

Master out slave in

MISO:

Master in slave out

CLK:

Clock signal 

CS/SS:

Chip select

 

MOSI ,MISO are communication lines like RX,TX lines(in which the master(controller) and slave(SPI display or device) establish communication

CLK/SCLK is the clock signal for synchronization.

CS- Is the one who plays the leading roll here. It is the one which initiate/trigger the communication  

So we can use this CS pin to solve the SPI pin limitation issues in the micro controllers . 

i.e By putting logic in CS pin we can share the MISO,MOSI pins with multiple devices.

The figure below shows the example connection diagram

Connection diagram for multiple SPI device with single controller

yaah, we are just shorting  it!

"sharing is caring👻"

If you want to connect N number of devices you only need 3+N number of pins

All MISO lines are shorted together and connected to MISO supported pin of our  micro-controller.

 All MOSI lines are shorted together and connected to MOSI supported pin of our micro controller.

All CLK/SCLK  lines are shorted with Clk pin in micro-controller

And CS/SS pins are connected to individual pins of the micro-controller .

now the CS pin will decide which slave/SPI device should communicate with the micro-controller. 

 To send data from the master device to the slave device, you first need to set the SS/CS pin on the

 master device to LOW, and keep it LOW for the duration of the data exchange. This prepares the slave

 device to send or receive data. Once the SS/CS pin is LOW, the master can send data over the MOSI line

 and simultaneously produce clock pulses from the SCLK pin.

SPI display L SPI device Pin diagram