5. SPI

5.1 Introduction

• SPI stands for Serial Peripheral Interface, which is a high-speed, full-duplex, synchronous communication bus.

• It operates in a master-slave mode, where typically one master device corresponds to one or more slave devices. It requires 4 wires for bidirectional data transfer and can be reduced to 3 wires for unidirectional data transfer.

• The SPI bus consists of four physical connections: two data lines, one clock line, and a slave select line.

  • MOSI (Master Output/Slave Input) – The line through which the Core3566 sends data to the device (sensor).

  • MISO (Master Input/Slave Output) – The line through which the device sends data to the Core3566.

  • SCLK (Clock) – The clock signal line.

  • SS/CS (Slave Select/Chip Select) – The line used to select the device to which data is being sent.

• Core3566 has two SPI interfaces, namely SPI1 and SPI3.

5.2 Enabling the SPI Interface

• The process of enabling the SPI interface is similar to I2C. Simply select SPI.

  ┌────────────┤ luckfox Software Configuration Tool (luckfox-config) ├────────────┐
  │                                                                                │
  │         P1 SPI1 Enable/disable automatic loading of SPI1 kernel module         │
  │         P2 SPI3 Enable/disable automatic loading of SPI3 kernel module         │
  │                                                                                │
  │                                                                                │
  │                                                                                │
  │                                                                                │
  │                                                                                │
  │                     <Select>                     <Back>                        │
  │                                                                                │
  └────────────────────────────────────────────────────────────────────────────────┘

• Use the ls command to check if the enablement was successful:

  linaro@linaro-alip:~$ ls /dev/spi*
  /dev/spidev1.0  /dev/spidev1.1

5.3 Hardware Connection

• Pin connections for Core3566:

  1.5inch OLED Module	Core3566 Board Physical Pin Number	Function
  VCC	3V3	Power input
  GND	GND	Power ground
  DIN	SPI1_MOSI	Master Output/Slave Input
  CLK	SPI1_CLK	SPI Clock signal
  CS	SPI1_CS0	Chip select
  DC	GPIO3_A3	Data/Command select
  RST	GPIO3_C4	Reset

• Wiring Diagram.
  

5.4 Controlling with Python Program

• Download the experiment code and run the program in the terminal:

  cd ~/OLED_1in5/
  sudo python3 OLED_1in5_spi.py