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Lecture 45 : PIC Serial Communication using Serial Peripheral Interface (SPI)

Saturday October 7, 2017 / Ibrar Ayyub
Categories: Interfacing(USB - RS232 - I2c -ISP) Projects
Tags: Lecture 45 PIC Serial Communication using Serial Peripheral Interface (SPI) Schematic
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1 Summary of Lecture 45 : PIC Serial Communication using Serial Peripheral Interface (SPI)
1.1 Parts used in the PIC16F877A SPI Serial Communication Project:

Summary of Lecture 45 : PIC Serial Communication using Serial Peripheral Interface (SPI)


This project establishes SPI serial communication between two PIC16F877A microcontrollers. The master microcontroller reads an 8-bit digital input from Port B and transmits it via SPI to the slave microcontroller. Using SPI lines (SDO, SDI, SCK), the slave receives the data and outputs it to its Port B. The communication is configured through the SSPCON register, enabling SPI mode with appropriate clock settings. The process uses interrupts on the slave side to handle incoming data and continuously repeats transmission on the master side.

Parts used in the PIC16F877A SPI Serial Communication Project:

  • PIC16F877A microcontroller (master)
  • PIC16F877A microcontroller (slave)
  • Digital input source (connected to Port B of master)
  • Wiring for Serial Data Out (SDO) line
  • Wiring for Serial Data In (SDI) line
  • Wiring for Serial Clock (SCK) line
  • Power supply for PIC microcontrollers

Objective

To establish serial communication between two PIC16F877A microcontrollers

Description
In this experiment, 8-bit digital input is applied at Port-B to one of the PIC16F877A microcontroller which acts as a master in serial communication. The input value is transmitted by the master serially via Serial Peripheral Interface (SPI) to the second PIC16F877A microcontroller, which acts as a slave. The slave then outputs the value to its Port-B. Following three lines are used for serial communication
  1. Serial Data Out (SDO)
  2. Serial Data In (SDI)
  3. Serial Clock (SCK)

Lecture 45 PIC Serial Communication using Serial Peripheral Interface (SPI) Schematic

The SDO for master acts as SDI for slave and vice-versa. Serial clock is invariably provided by the master. The SPI communication settings are done using SSPCON register.

SSPEN = 1                                         , Enables serial communication in SPI mode
CKP = 1                                              , Transmit happens on falling edge, receive on rising edge
SSPM3-SSPM0 = 0000                   , Device set in master mode with clock = Fosc/4
SSPM3-SSPM0 = 0100                   , Device set in slave mode with clock = SCK pin

Transmission is initiated by the Master by writing to the SSPBUF register. When transfer is complete, Synchronous Serial Port Interface Flag (SSPIF) will be set. This can cause an interrupt if peripheral interrupt is enabled.

Assembly Code

Master microcontroller code
; This program reads Port B value from Master PIC microcontroller
; and sends it to slave PIC microcontroller

org 0000H                                                  ; Reset address

Mainline:

movlw 00110000b                                    ; Enable SPI mode, clock, master
movwf SSPCON
movf PortB, W                                            ; Read PortB value
movwf SSPBUF                                         ;  Transmit value to slave
nop
nop
nop
goto Mainline                                            ; Repeat the process

; Slave microcontroller code
; This program receives 8-bit value from Master PIC microcontroller
; and sends it to Port B of slave PIC microcontroller

Lecture 45 PIC Serial Communication using Serial Peripheral Interface (SPI) Schematic

org 0000H                                                 ; Reset address
goto Mainline

org 0020H                                                 ; main program address

Mainline:           bsf STATUS, RP0                                     ; Bank 1

bsf PIE1, SSPIE                                       ; Enable SSP interrupt
bcf STATUS, RP0                                    ; Bank 0
bcf PIR1, SSPIF                                       ; clear SSP interrupt flag
bsf INTCON, PEIE                                   ; Enable peripheral interrupt
bsf INTCON, GIE                                     ; Enable global interrupt

loop:                   goto loop                                                   ; Infinite loop

org 0004H                                                 ; Interrupt sub-routine address
movf SSPBUF, W                                     ; Read SSPBUF
movwf PortB                                              ; write SSPBUF value to Port B
retie                                                             ; Return

 

For more detail: Lecture 45  PIC Serial Communication using Serial Peripheral Interface (SPI) Schematic


About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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