1. Advanced Microcontrollers A practical approach lesson 2 serial communication

2. Microcontrollers A practical approach
Topics
Some about architecture
Serial communication

3. Microcontrollers serial communication A practical approach
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

4. Microcontrollers serial communication A practical approach
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))

5. RS232 connectorA practical approach
(PC))
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

6. RS232 voltagesA practical approach
Level
Transmitter (V)
Receiver (V)
Space status (0)
Mark status (1)
Not defined - …

7. RS232 cablelenghtA practical approach
Baud rate
Maximum cabellength(m)
19200 15
9600
150
4800
300
2400
900

8. Serial communiaction A practical approach
Topics
PIC family
Architecture PIC18F2580
Interrupts
Serial communication
LCD
Assembly
A very little microcontroller

9. PIC18 UARTpractical approach
• Asynchronous
- Auto-wake-up
- Auto baud calibration
- 13-bit Break character
• Synchronous –
selectable clock
clock polarity

10. Baud ratepractical approach

11. PIC18F2580 pinout

12. Programming Header Functions Main program Initialisation…
Main program
Initialisation (function call)
Program with function calls in infinite loop

13. Program header
/*********************** pic18f2580 **********************************\
| Testprogram_ MPlab C18-compiler |
| 11 sept 2012/21 juli 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 |
\**************************************************************************/

14. 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 code
void main (void)
{ TRISC=0; //led's output tx output
InitINT0();
InitUART();
InitTimer0();
EnableHighInterrupts();
// run forever:
while(1) {
//do nothing} }

15. Iniatalisation RB0 #pragma code void 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 edge
INTCONbits.PEIE = 1; // enable high priority interrupt
INTCONbits.INT0IE = 1; // enable INT0 }

16. Initialisation UART void InitUART(void) { // setup UART:
SPBRGH=0; SPBRG=31; // interne clock Fosc=20MHz -> // Baud p error 0,16%
TXSTAbits.SYNC = 0; // Enable asynchronous serial port
RCSTAbits.SPEN = 1; // Enable asynchronous serial port
TXSTAbits.TXEN = 1; // Enable transmission; als
puts("\rUART initialised\r"); // To Pc OR BLUETOOTH }
For initialisation timer see lesson 1

17. Initialisation interrupt
void EnableHighInterrupts(void) {
RCONbits.IPEN = 1; // enable interrupt priority levels
INTCONbits.GIEH = 1; // enable all high priority iterrupts }
// High priority interrupt vextor:
#pragma code high_vector = 0x08
void high_interrupt(void)
_asm goto InterruptHandlerHigh _endasm

18. Interrupt Service Routine
#pragma interrupt InterruptHandlerHigh
void InterruptHandlerHigh(void) {
if(INTCONbits.TMR0IF) // check for TMR0 overflow
INTCONbits.TMR0IF = 0; // clear interrupt flag
TMR0H = 72; // reload timer
TMR0L = 229; // reload timer
PORTCbits.RC2 = !PORTCbits.RC2; // toggle LED on RC2
PORTBbits.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

19. 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 }

20. Assignments lesson 2 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
Make the recieving program working:
Connect two boards let them communicate