PC/CP 364- Serial Communication-UARTdenethor.wlu.ca/pc364/uartbeam.pdf · 2016-12-15 · Arduino Serial Library Baud rate calculation RS232 communication Baud rate calculation Baud

Serial Communication -UARTArduino Serial Library

PC/CP 364Serial Communication-UART

Terry Sturtevant

Wilfrid Laurier University

December 15, 2016

Terry Sturtevant PC/CP 364 Serial Communication-UART


Baud rate calculationRS232 communication

Serial Communication -UART

Universal Asynchronous Receiver TransmitterSimplest form of serial communicationBetween 2 devicesUses 2 signals (and Ground), Rx and TxAsynchronous, so both must agree on baud rate





Universal Asynchronous Receiver Transmitter

Simplest form of serial communicationBetween 2 devicesUses 2 signals (and Ground), Rx and TxAsynchronous, so both must agree on baud rate





Universal Asynchronous Receiver TransmitterSimplest form of serial communication

Between 2 devicesUses 2 signals (and Ground), Rx and TxAsynchronous, so both must agree on baud rate





Universal Asynchronous Receiver TransmitterSimplest form of serial communicationBetween 2 devices

Uses 2 signals (and Ground), Rx and TxAsynchronous, so both must agree on baud rate





Universal Asynchronous Receiver TransmitterSimplest form of serial communicationBetween 2 devicesUses 2 signals (and Ground), Rx and Tx

Asynchronous, so both must agree on baud rate





Universal Asynchronous Receiver TransmitterSimplest form of serial communicationBetween 2 devicesUses 2 signals (and Ground), Rx and TxAsynchronous, so both must agree on baud rate




Communication parameters

1 Start bit at “0” levelLSB transmitted firstCan have odd, even, or no parity bit1 or 2 Stop bits at “1” level

Since start and stop bits are opposite, new characters can alwaysbe detected.





1 Start bit at “0” level

LSB transmitted firstCan have odd, even, or no parity bit1 or 2 Stop bits at “1” level






1 Start bit at “0” levelLSB transmitted first

Can have odd, even, or no parity bit1 or 2 Stop bits at “1” level






1 Start bit at “0” levelLSB transmitted firstCan have odd, even, or no parity bit

1 or 2 Stop bits at “1” level




















Start




Start

0

LSB

1




Start

0

LSB

1

1 1




Start

0

LSB

1 2

1 1 1




Start

0

LSB

1 2 3

1 1 1 0




Start

0

LSB

1 2 3 4

1 1 1 0 0




Start

0

LSB

1 2 3 4 5

1 1 1 0 0 1




Start

0

LSB

1 2 3 4 5 6

1 1 1 0 0 1 1




Start

0

LSB

1 2 3 4 5 6 7

MSB

1 1 1 0 0 1 1 0




Start Stop

0

LSB

1 2 3 4 5 6 7

MSB

1 1 1 0 0 1 1 0




Start Stop

0

LSB

1 2 3 4 5 6 7

MSB

1 1 1 0 0 1 1 0

UART no parity - 01100111




Start Stop

Parity0 1 2 3 4 5 6 7

UART even parity




Start Stop

Parity0 1 2 3 4 5 6 7

UART even parity




Start Stop

Parity0 1 2 3 4 5 6 7

UART odd parity




Baud rate calculation

Baud rate is the number of bits possible in a seconde.g. 9600 baud → 1 bit takes 1

9600 secondAfter start bit is detected, wait time for 11

2 bit to testfor first data bit and then after every 1 bit intervalResetting at the start bit allows some clock variation





Baud rate is the number of bits possible in a second

e.g. 9600 baud → 1 bit takes 19600 second

After start bit is detected, wait time for 112 bit to test

for first data bit and then after every 1 bit intervalResetting at the start bit allows some clock variation






9600 second

After start bit is detected, wait time for 112 bit to test

for first data bit and then after every 1 bit intervalResetting at the start bit allows some clock variation







2 bit to testfor first data bit and then after every 1 bit interval

Resetting at the start bit allows some clock variation







2 bit to testfor first data bit and then after every 1 bit intervalResetting at the start bit allows some clock variation







Start




Start

0

1




Start

0 1

1 1




Start

0 1 2

1 1 1




Start

0 1 2 3

1 1 1 0




Start

0 1 2 3 4

1 1 1 0 0




Start

0 1 2 3 4 5

1 1 1 0 0 1




Start

0 1 2 3 4 5 6

1 1 1 0 0 1 1




Start

0 1 2 3 4 5 6 7

1 1 1 0 0 1 1 0




Start Stop

0 1 2 3 4 5 6 7

1 1 1 0 0 1 1 0




Start Stop

0 1 2 3 4 5 6 7

1 1 1 0 0 1 1 0

Bit timing




RS232 communication

Voltages are inverted±3→ ±12Zero is not a valid voltageMark level (inactive/1) is a negative voltageSpace level (active/0) is a positive voltage




RS232 communication

Voltages are inverted

±3→ ±12Zero is not a valid voltageMark level (inactive/1) is a negative voltageSpace level (active/0) is a positive voltage




RS232 communication

Voltages are inverted±3→ ±12

Zero is not a valid voltageMark level (inactive/1) is a negative voltageSpace level (active/0) is a positive voltage




RS232 communication

Voltages are inverted±3→ ±12Zero is not a valid voltage

Mark level (inactive/1) is a negative voltageSpace level (active/0) is a positive voltage




RS232 communication

Voltages are inverted±3→ ±12Zero is not a valid voltageMark level (inactive/1) is a negative voltage

Space level (active/0) is a positive voltage




RS232 communication

Voltages are inverted±3→ ±12Zero is not a valid voltageMark level (inactive/1) is a negative voltageSpace level (active/0) is a positive voltage




ParityMark 0 1 2 3 4 5 6 7




Start

ParityMark

Space

0 1 2 3 4 5 6 7




Start Stop

ParityMark

Space

0 1 2 3 4 5 6 7




Start Stop

ParityMark

Space

0 1 2 3 4 5 6 7

RS232 levels



Arduino Serial

Serial.begin(9600)start port and set baudratewhile(!Serial)wait to connectif (Serial.available() > 0)returns True if data available, False if not



Arduino Serial

Serial.begin(9600)start port and set baudrate

while(!Serial)wait to connectif (Serial.available() > 0)returns True if data available, False if not



Arduino Serial

Serial.begin(9600)start port and set baudratewhile(!Serial)wait to connect

if (Serial.available() > 0)returns True if data available, False if not



Arduino Serial

Serial.begin(9600)start port and set baudratewhile(!Serial)wait to connectif (Serial.available() > 0)returns True if data available, False if not



Arduino Serial (continued)

Serial.write(value)write valueSerial.print(’A’)write string as ASCIIinByte = Serial.read()read byteSerial.end()close port




Serial.write(value)write value

Serial.print(’A’)write string as ASCIIinByte = Serial.read()read byteSerial.end()close port




Serial.write(value)write valueSerial.print(’A’)write string as ASCII

inByte = Serial.read()read byteSerial.end()close port




Serial.write(value)write valueSerial.print(’A’)write string as ASCIIinByte = Serial.read()read byte

Serial.end()close port




Serial.write(value)write valueSerial.print(’A’)write string as ASCIIinByte = Serial.read()read byteSerial.end()close port



Arduino Serial sample code

v o i d s e t u p ( ) {S e r i a l . b e g i n ( 9 6 0 0 ) ;w h i l e ( ! S e r i a l ) {

;}

}

v o i d l o o p ( ) {i f ( S e r i a l . a v a i l a b l e ( ) > 0) {

i n B y t e = S e r i a l . r e a d ( ) ;S e r i a l . w r i t e ( i n B y t e ) ;}

}



Arduino Serial sample code

v o i d s e t u p ( ) {S e r i a l . b e g i n ( 9 6 0 0 ) ;w h i l e ( ! S e r i a l ) {

;}

}

v o i d l o o p ( ) {i f ( S e r i a l . a v a i l a b l e ( ) > 0) {

i n B y t e = S e r i a l . r e a d ( ) ;S e r i a l . w r i t e ( i n B y t e ) ;}

}


Documents

PC/CP 364- Serial Communication-UARTdenethor.wlu.ca/pc364/uartbeam.pdf · 2016-12-15 · Arduino Serial Library Baud rate calculation RS232 communication Baud rate calculation Baud