Saxion University of Applied Sciences Advanced Microcontrollers A practical approach lesson 2 serial communication.

Saxion University of Applied Sciences

Advanced MicrocontrollersA practical approach

lesson 2 serial communication

Microcontroller programming

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Topics Some about architecture Serial communication

MicrocontrollersA practical approach

Microcontroller programming

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Morse code telegraphy RS-232 (low-speed, implemented by Serial Ports) RS485 Universal Serial Bus (moderate-speed, for

connecting computers to peripherals) FireWire Fibre Channel (high-speed, for connecting

computers to mass storage devices) InfiniBand (very high speed, broadly comparable in

scope to PCI) Serial Attached SCSI Serial ATA PCI Express CAN

Microcontrollers serial communicationA practical approach

Microcontroller programming

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Half duplex Full duplex 5,6,7,8 databits ASCII (0-127) Stop bit(s) Parity DCE (Data communication equipment) DTE(Data terminal Equipment (PC))

Microcontrollers serial communicationA practical approach

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(PC))

RS232 connectorA practical approach 9 Pin Connector on a DTE device (PC connection)

Male RS232 DB9

Pin Number Direction of signal:

1 Carrier Detect (CD) (from DCE) Incoming signal from a modem

2 Received Data (RD) Incoming Data from a DCE

3 Transmitted Data (TD) Outgoing Data to a DCE

4 Data Terminal Ready (DTR) Outgoing handshaking signal

5 Signal Ground Common reference voltage

6 Data Set Ready (DSR) Incoming handshaking signal

7 Request To Send (RTS) Outgoing flow control signal

8 Clear To Send (CTS) Incoming flow control signal

9 Ring Indicator (RI) (from DCE) Incoming signal from a modem

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RS232 voltagesA practical approach

Level Transmitter (V)

Receiver (V)

Space status (0) +5 ... +15 +3 ... +25

Mark status (1) -5 ... -15 -3 ... -25

Not defined - -3 .. -3 …+3 . +3

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RS232 cablelenghtA practical approach

Baud rate Maximum cabellength(m)

19200 15

9600 150

4800 300

2400 900

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Topics PIC family Architecture PIC18F2580 Interrupts Serial communication LCD Assembly A very little microcontroller

Serial communiactionA practical approach

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PIC18 UARTpractical approach • Asynchronous

- Auto-wake-up

- Auto baud calibration

- 13-bit Break character

• Synchronous –

selectable clock

• Synchronous –

clock polarity

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Baud ratepractical approach

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PIC18F2580 pinout

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Programming

Header Functions

Initialisation…

Main program1. Initialisation (function call)2. Program with function calls in

infinite loop

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/*********************** pic18f2580 **********************************\| Testprogram_1 MPlab C18-compiler || 11 sept 2012/21 juli 2013 J.S.D. Stokkink |+-----------------------------------------------------------------------------------+| Gebruit van INT0 , TIMER0 , UART , High-iterrupt priority |+-----------------------------------------------------------------------------------+| WERKING: || RB0 via schakelaar naar GND geeft INT0 interrupt text to ser|| ial port TX pin || TIMER0 is ingesteld op ca 1sec || De Xtal frequentie is 20MHz || After InitUART() ,putc(c,stdout) and puts("string") || De op RB2 aangesloten LED zal knipperen met ca 1Hz |\**************************************************************************/

Program header

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Main Program send serial#include <p18F2580.h>#include <stdio.h> // t.b.v. puts() en putc() functies#pragma config OSC = HS // HS oscillator 20 Mhz#pragma config WDT = OFF // Watchdog Timer disabled#pragma config LVP = OFF // Low Voltage ICSP disabled#pragma config PBADEN = OFF // PortB<4:0> configured as digital I/O// Function-declarations:void InterruptHandlerHigh(void);void InitINT0(void);void InitUART(void);void InitTimer0(void);void EnableHighInterrupts(void);

// Globale variabelen:char ch = '0'; //start with character '0'#pragma codevoid main (void){ TRISC=0; //led's output tx output

InitINT0();InitUART();InitTimer0();EnableHighInterrupts();

// run forever: while(1) { //do nothing}}

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Iniatalisation RB0#pragma codevoid InitINT0(void){

PORTB = 0; // clear PORT B TRISB = 0x01; // RB0=input; RB1-7: output INTCON2bits.RBPU=0; // pull-ups portB enabled

INTCON2bits.INTEDG0 =1; // interrupt on rising edgeINTCONbits.PEIE = 1; // enable high priority interruptINTCONbits.INT0IE = 1; // enable INT0

}

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Initialisation UARTvoid InitUART(void){

// setup UART:SPBRGH=0; SPBRG=31; // interne clock Fosc=20MHz ->9600

// Baud p error 0,16%TXSTAbits.SYNC = 0; // Enable asynchronous serial portRCSTAbits.SPEN = 1; // Enable asynchronous serial portTXSTAbits.TXEN = 1; // Enable transmission; alsputs("\rUART initialised\r"); // To Pc OR BLUETOOTH

}

For initialisation timer see lesson 1

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Initialisation interruptvoid EnableHighInterrupts(void){

RCONbits.IPEN = 1; // enable interrupt priority levelsINTCONbits.GIEH = 1; // enable all high priority iterrupts

}

// High priority interrupt vextor:#pragma code high_vector = 0x08void high_interrupt(void){

_asm goto InterruptHandlerHigh _endasm}

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Interrupt Service Routine#pragma interrupt InterruptHandlerHighvoid InterruptHandlerHigh(void){

if(INTCONbits.TMR0IF) // check for TMR0 overflow{

INTCONbits.TMR0IF = 0; // clear interrupt flagTMR0H = 72; // reload timerTMR0L = 229; // reload timerPORTCbits.RC2 = !PORTCbits.RC2; // toggle LED on RC2PORTBbits.RB3 = !PORTBbits.RB3; // toggle LED on RC2

ch++; //next character (see ASCII table)putc(ch,stdout); // ASCII-karakter naar PC}if(INTCONbits.INT0IF) // check for INT0 flag {INTCONbits.INT0IF =0; // clear interrupt INT0 (RB0) flag puts("\n"); puts("\rRB0 pressed\r"); // to PC}

}

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Extra part ISR for recieve if (PIR1bits.RCIF == 1) //check for recieve interrupt { TXSTAbits.TXEN=0; // transmitter off if (RCREG=='a') {PORTCbits.RC0=1; puts(" end \r ");} //LED on if (RCREG=='b') PORTCbits.RC0=0; //read receiverif character = ‘b' LED of TXSTAbits.TXEN=1; // transmitter on PIR1bits.RCIF=0; // interrupt flag off }

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Assignments lesson 2

1. Make the send serial example working : a. check the output on a scoop. (explain) RS232 output and 5v output b.Checkthe output on a terminal(via USB

or Bluetooth) (install terminal program on your

phone(BT) or PC 2. Make the recieving program working:3. Connect two boards let them

communicate