THE RCAN-ET PERIPHERAL AND THE CAN API · The RCAN-ET peripheral and the CAN API SH2 & SH2AMCUs V 1.2 Mar 2010 ... Allow user to leave quiz: At any time User may view slides after

© 2008, Renesas Technology America, Inc.

All Rights Reserved

The RCAN-ET peripheral and the CAN API

SH2 & SH2A MCUs

V 1.2 Mar 2010

© 2010, Renesas Technology America, Inc., All Rights Reserved2

Course Introduction

� Purpose

This course explains features of the CAN peripheral “RCAN-ET” anddiscusses usage of the firmware CAN API for the SH2 and SH2A MCUs.

� Objective

� Learn about the features of the R-CAN ET peripheral

� Grasp the overall structure of the Mailbox

� See what the CAN API offers

� Learn the difference in receiving and transmitting when usingPolled vs. interrupt design

� Understand basic error handling, and what test modes are available

� Content

� 25 pages

� 3 questions

� Learning Time

� 20 minutes


� Compliant with

� Bosch CAN specification 2.0B

� ISO-11898-1

� Clocked 20 to 50 MHz for CAN data rate up to 1Mbit/s

� One receive filter mask per mailbox

� ‘Mailbox’ = CAN message ‘Buffer’ = ‘Slot’ = A place where a CAN dataframe is stored

Features


Features!

� Transmit message queuing by:

� Regular CAN arbitration mechanism

� Mailbox number

� Sleep mode for low power consumption:

� Automatic recovery from sleep mode by detecting CAN bus activity

� Manual recovery from sleep mode


The RCAN-ET Peripheral


The Mailbox

� 16 mailboxes (slots) - 15 transmit/receive & 1 receive-only.

� Mailbox attributes to be set by user application:

� Extended/Standard ID [IDE], Remote request flag [RTR], Message ID.

� Acceptance Filter Mask [LAFM].

� Data content if transmission mailbox [MSG_DATA_0-7].

� New Message Control [NMC]: Overwrite or keep old if message not read in time.

� Mailbox Control [MBC]; configure as transmit/receive/remote mailbox.

� CAN API functions take care of setting attributes - User need not know details!

PROPERTIES

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Interrupts

� Interrupt causes

� Receive complete

� Transmit complete

� Errors

– Message error

– Transition to states

� Error Warning

� Error Passive

� Bus Off

� CAN Reset, Halt, Sleep/Wake transition

� Remote frame reception

� Message overrun

� Overload frame sent

Interrupt service routines must be declared with “#pragma” in vect.h#pragma INTERRUPT INT_RCANET0_ERS_0()

#pragma INTERRUPT INT_RCANET0_OVR_0()

#pragma INTERRUPT INT_RCANET0_RM_0

#pragma INTERRUPT INT_RCANET0_SLE_0 ()


Interrupts

� Four Interrupt vectors: 104-107.

� Actual interrupt cause is read inside ISR by reading IRR flags:

� Int#104:

� Int#105:

� Int#106:

� Int#107:


� Layers: Hardware (bottom) to application software (top).

� Application would prefer to interface only to a simple CAN API.

=> Not bother with low level details.

Layers

Application

CANopen, Devicenet, J1939

CAN API

CAN peripheral

MCU / transceiver / bus

Optional industrial protocol

(not necessary)

PROPERTIES




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The CAN API

The CAN API


CAN Initialization

Top level function call to CAN setup functions

� Enable the CAN peripheral.

� Enter CAN Reset state.

� Initialize all mailboxes.

� Set all mailboxes’ masks.

� Configure the CAN interrupts.

� Set the bitrate.

� Exit CAN Reset state.

� Enable CAN ports.

voidvoidvoidvoidR_CAN_Initial ( void )R_CAN_Initial ( void )R_CAN_Initial ( void )R_CAN_Initial ( void )

The CAN API


Data Frame Transmit

Set up a mailbox to transmit a CAN dataframe

� If previously a receive mailbox, enter halt mode.

� Setup ID, DLC for the mailbox.

� Set mailbox to transmit mode. (MB 0 cannot transmit.)

� Write data frame payload.

� Enable mailbox Tx-interrupt unless USE_CAN_POLL was defined.

� Request transmission.

voidvoidvoidvoidR_CAN_SetTxStdData ( uint8_t mbx_nr, R_CAN_SetTxStdData ( uint8_t mbx_nr, R_CAN_SetTxStdData ( uint8_t mbx_nr, R_CAN_SetTxStdData ( uint8_t mbx_nr,

can_std_frame_t* tx_dataframe_p )can_std_frame_t* tx_dataframe_p )can_std_frame_t* tx_dataframe_p )can_std_frame_t* tx_dataframe_p )

The CAN API


Data Frame Transmit Verification

Transmit verification

� Not necessary

� When message is sent - flag main application

Do not define USE_CAN_POLL

Successful data frame transmit automatically triggers ISR

INT_RCANET0_SLE_0()INT_RCANET0_SLE_0()INT_RCANET0_SLE_0()INT_RCANET0_SLE_0()

Flag main program that data was sent.

Define USE_CAN_POLL

Check if data received by regularly calling

R_CAN_CheckTxStdDataR_CAN_CheckTxStdDataR_CAN_CheckTxStdDataR_CAN_CheckTxStdData()

If returns API_OK, message sent.

Two methods available

� Polling

� Transmit complete interrupt


Configure Mailbox to Receive

Set up a mailbox to receive

� Enter CAN Halt state

� Set specified receive CAN ID for specified mailbox

� Set to receive to use the mailbox mask

� Overwrite mode set

� Receive interrupt enabled unless USE_CAN_POLL defined

voidvoidvoidvoidR_CAN_SetRxStdData ( uint8_t mbx_nr, const int16_t sid )R_CAN_SetRxStdData ( uint8_t mbx_nr, const int16_t sid )R_CAN_SetRxStdData ( uint8_t mbx_nr, const int16_t sid )R_CAN_SetRxStdData ( uint8_t mbx_nr, const int16_t sid )

The CAN API


Receive using Polling or Interrupt

Do not define USE_CAN_POLL

Successful data frame receive automatically triggers ISR

INT_RCANET0_RM_0( )INT_RCANET0_RM_0( )INT_RCANET0_RM_0( )INT_RCANET0_RM_0( )

Copy data to buffer and flag main program that data was received.

Define USE_CAN_POLL

Check if data received by regularly calling

R_CAN_CheckRxStdData()

If yes, process received message

Two methods available

� Receive by polling

� Receive using receive interrupt

The CAN API


� Poll function confirms checks if a framed was received

� Use also from receive interrupt to check which mailbox received

� If message received, call this!

� Reads frame from given mailbox

� Writes frame to given address

� Checks for overwrite/overrun

Data Frame Receive

uint32_t uint32_t uint32_t uint32_t R_CAN0_PollRxCAN ( uint32_t mbx_nr)R_CAN0_PollRxCAN ( uint32_t mbx_nr)R_CAN0_PollRxCAN ( uint32_t mbx_nr)R_CAN0_PollRxCAN ( uint32_t mbx_nr)

The CAN API

voidvoidvoidvoidR_CAN0_ReadCanMsg ( uint32_t mbx_nr, R_CAN0_ReadCanMsg ( uint32_t mbx_nr, R_CAN0_ReadCanMsg ( uint32_t mbx_nr, R_CAN0_ReadCanMsg ( uint32_t mbx_nr,

can_std_frame_t*can_std_frame_t*can_std_frame_t*can_std_frame_t* frame_p)frame_p)frame_p)frame_p)


Mask Setting

One mask per mailbox

� Receive one ID: Set all mask bits to ‘1’

� Accept all messages: Set all mask bits to ‘0’ (don’t care)

� Accept range of IDs: Set selected bits to ‘0’ (don’t care)

voidvoidvoidvoidset_mask_can ( void )set_mask_can ( void )set_mask_can ( void )set_mask_can ( void )

The CAN API


Error Handling

Check CAN error state regularly

� This function returns one of

� STATE_NO_ERROR (Error Active): OK!

� STATE_ERROR (Error Active): One or more errors occurred, no need

to take action!

� STATE_ERROR_PASSIVE: Over 127 errors occurred – warn user!

� STATE_BUSOFF: Node will not transmit until it recovers.

notify user that node is not working and

restart application when unit returns to

Error Active.

uint8_tuint8_tuint8_tuint8_tR_CAN_CheckErr ( void )R_CAN_CheckErr ( void )R_CAN_CheckErr ( void )R_CAN_CheckErr ( void )

The CAN API


Application Handling of Bus Off

Bus Off reached

Peripheral recovered:

Reinitialize CAN peripheral and

slots

Normal application activity

Poll if peripheral is in Bus Off

Application can not send or receive

System goes into error mode:

Poll if peripheral recovers


Loopback - Self Test Mode 1

Transmit slot

Receive slot

CAN bus

Message transmission

Same ID set for

transmit

and receive slot

Node can acknowledge its own data,

and receive sent data to another

mailbox via CAN bus

(Communicating node not necessary)


Loopback - Self Test Mode 2

Transmit slot

Receive slot

Message transmission

CAN bus

Same ID set for

transmit

and receive slot

Node can acknowledge its own data,

and receive sent data to another

mailbox without CAN bus

(Communicating node not necessary)


Listen Only Mode

Bus node

Bus nodeTransmitting

node

Bus node

Bus node

Node in

Listen Only

mode

Transmitting

Node

Node in

Listen Only

mode

Node

transmitting

frame

“Normal” node: ACK is output,

or, if communication error,

Error frame is output instead.

No ACK or Error

frame sent by

Listen Only node!

PROPERTIES




User may view slides after quiz: At any time



� The R-CAN ET peripheral features

� The Mailbox structure

� What the CAN API can do

� Polled vs. interrupt design

� Basic error handling

� CAN Test modes

Course Summary

http://www.renesasinteractive.com

Documents

THE RCAN-ET PERIPHERAL AND THE CAN API · The RCAN-ET peripheral and the CAN API SH2 & SH2AMCUs V 1.2 Mar 2010 ... Allow user to leave quiz: At any time User may view slides after