Overview

The primary aim of this documentation is to enable users to develop a slave node that can be controlled by any master node through SPI (Serial Peripheral Interface) communication. This documentation provides a comprehensive guide for configuring a microcontroller as a slave device, allowing external master devices to send commands and manage its functionalities via the SPI protocol.

SPI Overview

Key Features:

• Synchronous Communication.
• Master-Slave Architecture.
• Four Wire Interface: SPI utilizes four main signals for communication:
• MOSI (Master Out Slave In)
• MISO (Master In Slave Out)
• SCK (Serial Clock)
• SS (Slave Select)

Hardware Requirements

• AVR programmer
• 2 AVR microcontrollers
• LCD display
• Wires
• Resistors
• LEDs
• Dip switch or push-button switch

Software Setup

• Eclipse, CodeBlocks, or any compatible IDE
• AVR library for development
• Proteus simulator (if using simulation)

SPI Configuration in AVR

SPCR: SPI Control Register

• Bit 7 – SPIE: SPI Interrupt Enable bit
• Bit 6 – SPE: SPI Enable bit
• Bit 5 – DORD: Data Order bit
• Bit 4 – MSTR: Master/Slave Select bit
• Bit 3 – CPOL: Clock Polarity Select bit
• Bit 2 – CPHA: Clock Phase Select bit
• Bit 1:0 – SPR1: SPR0 SPI Clock Rate Select bits

SPSR: SPI Status Register

• Bit 7 – SPIF: SPI interrupt flag bit
• Bit 6 – WCOL: Write Collision Flag bit
• Bit 5:1 – Reserved Bits
• Bit 0 – SPI2X: Double SPI Speed bit

SPDR: SPI Data Register

• SPI Data register used to transfer data between the Register file and SPI Shift Register.
• Writing to the SPDR initiates data transmission.

To access the SPI configuration source code, click here.

Interfacing with Peripherals - SPI Communication

Master-Slave Communication Protocol

The master device communicates with the slave device by sending specific letters:

• For Master (sends to Slave):
• n: Turn on LED
• f: Turn off LED
• s: Request status of the switch (pressed or released)
• For Slave (sends to Master):
• p: Indicates the switch is pressed
• r: Indicates the switch is released

source code, click here.

• to be compeleted