Can And Can Fd

Controller Area Network Flexible Data

Increased length: up to 64 data bytes per data frame vs. 8 data bytes for Classical CAN
Increased speed: up to 5 Mbit/s

-RRS: Remote Request Substitution
-IDE
-EDL: Extended Data Length
-FDF: Flexible Data Rate Format
-BRS: Bit Rate Switch
-ESI: Error State Indicator

RRS: Remote Request Substitution
(always a dominant 0). The remote frames are not at all supported in CAN FD.
EDL: Extended Data Length
(always a recessive 1) for managing larger payloads and faster bit-rates in CAN FD.
FDF: Flexible Data Rate Format
(always a recessive 1) used to indicate Flexible data frame format usage.
BRS: Bit Rate Switch
helps determine the bit rate of a data frame.
Dominant 0 signifies that the arbitration rate for the CAN FD data frame is up to 1Mbit/sec.
Recessive 1 signifies a higher/faster arbitration rate for the CAN FD data frame ranging up to 5Mbit/sec.
ESI: Error State Indicator

A dominant 0 indicates the error-active mode.

A recessive 1 indicates the error-passive mode.

CRC: The Cyclic Redundancy Check is 17 bits long for up to 16 bytes of data or 21 bits for 20-64 bytes. Its length depends upon the length of EDL and DLC bits. CAN FD always uses 4-fixed stuff bits that improve communication reliability.

Controller Area Network. Created by Bosch. Communication could be started by any node

CAN It is multimaster. Frame size = 8 Bytes of data

• SOF: The Start of Frame is a 'dominant bit' '0' to tell the other nodes that a CAN node intends to talk
• ID: The ID is the frame identifier - lower values have higher priority
Message ID = Lower the value, higher the priority.
• RTR: distinguish data and remote frame(0=Data frame, 1=Remote frame)
• R1(Initiate Control): IDE to differentiate standard and extended frame. Always recessive bit, 1.
• R0(continue Control): Is used to differentiate CAN and a CAN-FD frame. Always recessive bit, 1.
• Control: determine data size and message ID length
• Data: The Data contains the data bytes aka payload, which includes CAN signals that can be extracted and decoded for information
Data frame = Standard frame(11 bit) or extended frame(29 bit)
• CRC: The Cyclic Redundancy Check is used to ensure data integrity
• CRC Delimiter: be ready for ACK. Recessive 1.
• ACK: The ACK slot indicates if the node has acknowledged and received the data correctly(Dominant 0 + Recessive 1)
ACK is when a msg is re

Simplex = Send > Receive
Full-duplex = Send > Receive, Receive < Send (At the same time is sending and receiving)
Half-duplex = Send > Receive, Receive < Send (Not possible at the same time is sending and receiving)
CAN is half-duplex

Parallel communication = N of bits > 1
Serial communication = N of bits = 1
CAN is serial communication protocol

Twisted pair = CanHigh and CanLow. It is twisted pair for noise immunity, Twisted pair ends with a 120 ohms resistor for impedance matching = minimize signal reflection

Logic 1 = Recessive bit = CANH and CANL are equal to 2.5 v

Logic 0 = Dominant bit = CANH equal to 3.5v CANL equal to 1.5 v

CAN speed = 1 MbPS. 1 MbPS at 40 mts

CAN is asynchronous = It can start to communicate whenever it wants.
Synchronous Communication – Each bit of data drive syncs with a clock signal and the master drives the clock signal means the master can only initiate data communication.

11 y 29 bit identifier

Data Frame, Remote Frame, Error Frame and Overload Frame

MCU It processes data from the Application layer to the network layer and vice versa.
CAN Controller takes care of the message reception and transmission, error detection and handling, etc.
CAN Transceiver converts the CAN controller data into bus level before sending it on CAN Bus and vice-versa.

NRZ (Non Return to Zero)

CAN standard allowed only 5 consecutive bits of same polarity and after that signal must change its polarity to check synchronization between transmitter and receiver. If any transmitter wants to send more than 5 consecutive bits then it must insert an opposite signal bit and it is called bit stuffing and this extra stuff bit is de-stuffed by receiver before data processing.

Bit error
Stuff error = More than 5 consecutive bits of the same polarity
CRC error =If the receiver found Calculated CRC is different from received CRC
Acknowledgment error = if the transmitter receive a recessive bit as ACK
Form Error = CAN Frame Format(CRC Delimeter, ACK Delimeter, EOF ,InterFrame Spaceand) if it is detected corrupted at receiver side

High Speed CAN Vs Low Speed CAN

-100 ohm resistance
-Maximum bit rate is 40K to 125 kbps
-For dominant signal transmission, CAN_H drives towards 5 v while CAN_L drives toward 0.
-Rececive 1 = CANL 5V and CANH 0V
-Dominant 0 = CANH 3.5V and CANL 1.5
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0x01 hardReset
0x02 keyOffOnReset
0x03 softReset

0x01 requestSeed
0x02 sendKey

0x00 enableRxAndTx
0x01 enableRxAndDisableTx
0x02 disableRxAndenableTx
0x03 disableRxAndTx

0x00 zeroSubFunction

0x01 Start Routine
0x02 Stop Routine
0x03 Request Routine Results

0x02 on
0x03 off

0x01 reportNumberOfDTCByStatusMask
0x02 reportDTCByStatusMask
0x06 reportDTCExtDataRecordByDTCNumber
0x0A reportSupportedDTC