This document discusses several data communication standards used in embedded systems, including RS-232, RS-422, RS-485, CAN, SPI, and I2C. It describes the key features and protocols of each standard. RS-232 is an older standard serial port that was commonly used to program microcontrollers but has been replaced by newer standards like JTAG and USB. RS-422 and RS-485 are balanced differential standards suitable for long-distance transmission over twisted pair cabling. CAN is a robust protocol developed for vehicle networks to interconnect electronic control units. SPI and I2C are common synchronous serial bus standards used for communication between integrated circuits.
2. EMBEDDED SYSTEMS-
RS 232 STANDARD
• Standard Serial Port – Back of PC
• Used to
– download the Program to Microcontroller
from PC
• Replaced by JTAG, USB
• Conversion Cable can be used
• Hyperterminal- PC to serial Port
K.BALAJI , AP/ECE, SSMCE
3. RS 232 STANDARD
• Sending DATA as bits – ‘1’ or ‘0’
• TTL – bit-’1’ : 5V
• TTL – bit- ‘0’ : 0V
• TTL Levels– not suitable for Long
distance transmission ????????????
• RS232- Bit - 1: -3V to -25V
• Bit – 0: +3V to +25 V
K.BALAJI , AP/ECE, SSMCE
11. RS 422 / RS 485
• RS 422 – MultiDrop Protocol
– One Central Control Unit can send
commands in parallel to 10 slaves
• RS 485 – MultiPoint Protocol
– All Nodes are equal
– Every Node has send and receive
capabilities
K.BALAJI , AP/ECE, SSMCE
13. CONTROLLER AREA NETWORK (CAN)
• CAN is a Protocol developed to
reduce wiring inside vehicles
• It is used to interconnect Engine
Control Unit, Transmission Control
Unit, Door Locks
K.BALAJI , AP/ECE, SSMCE
14. CAN PROTOCOL
• CASE-I: ONE NODE SENDS A
MESSAGE
– One Node Broadcast a message
– The receiving nodes test the identifier
– Accept if it is relevant
K.BALAJI , AP/ECE, SSMCE
15. CAN PROTOCOL
• CASE-II: MANY NODES SENDS A
MESSAGE
– One node is allowed to do a valid
Broadcats
– Using Arbitration Mechanism
– 0- called Dominant
– 1 – called Recessive
K.BALAJI , AP/ECE, SSMCE
18. FEATURES OF CAN
• Differential Signalling
• Resistant to noise
• NRZ Coding
K.BALAJI , AP/ECE, SSMCE
19. CAN DATA FRAME
• SOF- START OF FRAME
• 11 BIT IDENTIFIER
• RTR- TO TELL ANY OTHER NODE TO TRANSMIT
• CONTROL FIELD : 6 BITS
• DATA : 0 TO 64 BYTES
• CRC : TO CHECK ERROR
• 2 BIT ACKNOWLEDGEMENT FIELD
• 7 BIT END OF FRAME
K.BALAJI , AP/ECE, SSMCE