CAN In A Day

Managing a Mailbox HW takes care of rest  Tx mailbox: HW takes care of low level transmit details Transmit Write Write Write to do!. Receive Setup mailbox Write - -Receive Get message

CAN In A Day

Renesas Technology & Solution Portfolio

Microcontroller and Microprocessor Line-up

44 DMIPS, True Low Power Embedded Security, ASSP

25 DMIPS, Low Power

10 DMIPS, Capacitive Touch

 Industrial & Automotive, 150nm

 190µA/MHz, 0.3µA standby

 Industrial, 90nm

 200µA/MHz, 1.6µA deep standby

 Automotive & Industrial, 90nm

 600µA/MHz, 1.5µA standby

 Automotive & Industrial, 65nm

 500µA/MHz, 35µA deep standby

 Industrial, 40nm

 200µA/MHz, 0.3µA deep standby

 Industrial, 90nm

 1mA/MHz, 100µA standby

 Industrial & Automotive, 130nm

 144µA/MHz, 0.2µA standby

Smart Society Challenge

 You don’t have time to write and debug a reliable CAN driver

Solution

Use CAN and the CAN API!

Focus on your application!

Connect to the Smart Society with CAN!

 Where Use CAN!?

Learn how to

view and send CAN dataframes

The lab is straightforward

T h e CA N A P I

Where CAN is Best! – 4 min.

Mainly on-board comm.

Too expensive Poor noise immunity

CAN – Continuously Moving into New Fields

Lowest Levels

Dataframe and Mailbox

Data (Bytes)

0-8 bytes

C R C 15

A C K 1

 With two channels, 64 mailboxes to use on one bus

 More SW design flexibility

 Less runtime reconfiguring

Frame Resides in Mailbox

Managing a Mailbox

 HW takes care of rest

 Tx mailbox: HW takes care of low level transmit details

Transmit

Write Write Write

to do!

Receive

Setup mailbox

Write -

-Receive

Get message

Read Read Read

CAN Firmware & Peripheral Interaction

CAN Peripheral

Firmware

Node

Mask Mask

Mask

ID=5,Data= ,RX ID=5,Data=123, TX

Transceiver Transceiver Transceiver

123…

 Which of these do you need in order to setup a mailbox to transmit?

Application Level

 Let’s move up the layers.

Layers (Where are we?)

Optional industrial protocol

Dealing with the CAN Registers…

…can be tedious.

Sure would be nice to have…

CAN Initialization

START

Enter CAN reset/ initialization mode

CAN reset mode? NO YES

Enable CAN ports

Set CAN control register

- Loopback mode select bit

- Message order select bit

- Basic CAN mode select bit

- Bus error interrupt enable bit

Set CAN bit timing and baud rate

Set mask register

Go to CAN operation mode

CAN operation mode? NO Exit CAN sleep mode

Initialization, Port and Peripheral Control

R_CAN_Create (ch_nr);

R_CAN_SetBitrate (ch_nr);

R_CAN_PortSet (ch_nr, action_type); [action_type = ENABLE, DISABLE ]

R_CAN_Control (ch_nr, action_type); [action_type = ENTERSLEEP_CANMODE,

EXITSLEEP_CANMODE, RESET_CANMODE, HALT_CANMODE, OPERATE_CANMODE, CANPORT_TEST_LISTEN_ONLY,

CANPORT_TEST_0_EXT_LOOPBACK, CANPORT_TEST_1_INT_LOOPBACK,

R_CAN_RxSet (ch_nr, mbox_nr, stid, frame_type);

R_CAN_RxRead (ch_nr, mbox_nr, frame_p);

R_CAN_RxPoll (ch_nr, mbox_nr, frame_p);

The CAN API

T h e CA N A P I

 Polling

 You only need data at a certain execution path

 You don’t want CAN interrupts interfering some other task

 Note:

– Overrun  New message discarded – Overwrite  New message overwrites old

 For processing data as soon as it arrives

 When messages may not be lost - “linked” messages

 To avoid overwrite / overrun

Polling vs Interrupts

The API function

 Waits for previous frame to finish transmit

 Clears message control register

 Disables interrupts for mailbox

 Not necessary

 Example; message in a sequence

 Just continuously check for Error Passive/Bus Off

Transmit Verification

#define USE_CAN_POLL 0

Successful Dataframe transmit triggers ISR

 Polling

#define USE_CAN_POLL 1 (config_r_can_rapi.h)

Check if data sent by calling

API_status = R_CAN_TxCheck (ch_nr, mbox_nr);

If API_OK, message was sent!

 Transmit interrupt

 A CAN mailbox configured with an ID can later be reused to handle other IDs?

Question

The API

unless USE_CAN_POLL defined

Configure Mailbox to Receive

R_CAN_RxSet(ch_nr, mbox_nr, stid, frame_type);

T h e CA N A P I

Polling for Received Data

How to receive Dataframe in application

 At System Setup

#define USE_CAN_POLL 1

 When polling from app, use

R_CAN_RxPoll(ch_nr, mbox_nr, frame_p);

R_CAN_RxRead (ch_nr, mbox_nr, frame_p);

 Copies data to address -> frame_p.

Using the Receive Interrupt

How to receive Dataframe in application

 At System Setup

#define USE_CAN_POLL 0

 When frame arrives with ID set by API

the CAN Receive ISR triggers

R_CAN_RxPoll (ch_nr, mbox_nr, frame_p);

 If new frame, call

R_CAN_RxRead (ch_nr, mbox_nr, frame_p);

which copies the data to frame_p

 Set a flag to tell the main application that data has been received

Lab Setup

YRDK63N

A to mini-B USB cable

To PC for J-Link debug

J8

U A R T

LCD

5V DCNot necessary

CAN only needs 0-3.5 V

J-Link

Debug

Application Level Considerations

 No real addresses

 Messages broadcast to whomever happens to listen!

11-bit ID split into “user protocol” fields

Your CAN Application - Keep in Mind

Error Handling

uint8_t R_CAN_CheckErr(void)

 STATE_ERROR (Error Active): < 127 CAN transmit and

receive errors occurred, OK!

warn user.

 STATE_BUSOFF: Node will not transmit until it

recovers Pause application, notify user that node is not

working Reinitialize CAN and reset mailboxes when node

recovers to Error Active.

T h e CA N A P I

Minimum Application Handling of Bus Off

Bus Off reached

Peripheral recovered:

Reinitialize CAN!

Normal application activity

Poll if peripheral is in Bus Off

Application can not send or receive

Questions?

Smart Society Challenge

 You don’t have time to write and debug a reliable CAN driver

Solution

Use CAN and the CAN API!

Focus on your application!

Connect to the Smart Society with CAN!