CAN In A Day 2L01I. Renesas Electronics America Inc Renesas Electronics America Inc. All rights reserved.

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1 CAN In A Day 2L01I Renesas Electronics America Inc.

2 Renesas Technology & Solution Portfolio 2

3 Microcontroller and Microprocessor Line-up bit 8/16-bit 1200 DMIPS, Superscalar Automotive & Industrial, 65nm 600µA/MHz, 1.5µA standby 500 DMIPS, Low Power 32-Bit High Performance DSP, FPU with High Integration Automotive & Industrial, 90nm 600µA/MHz, 1.5µA standby 165 DMIPS, FPU, DSC Industrial, 90nm 200µA/MHz, 1.6µA deep standby 25 DMIPS, Low Power Industrial & Automotive, 150nm 190µA/MHz, 0.3µA standby 10 DMIPS, Capacitive Touch Wide Industrial Format & LCDs Automotive, 130nm 350µA/MHz, 1µA standby 1200 DMIPS, Performance Automotive, 40nm 500µA/MHz, 35µA deep standby 165 DMIPS, FPU, DSC Industrial, 40nm 200µA/MHz, 0.3µA deep standby Embedded Security, ASSP Industrial, 90nm 1mA/MHz, 100µA standby 44 DMIPS, True Low Power Industrial & Automotive, 130nm 144µA/MHz, 0.2µA standby 3

4 Connect to the Smart Society with CAN! Smart Society Challenge You don t have time to write and debug a reliable CAN driver You need to get your idea to market SOON Solution Use CAN and the CAN API! The CAN API handles controlling the peripheral The CAN peripheral - Handles ALL the low level details Focus on your application! 4 Agenda

5 Agenda Where Use CAN!? The CAN Dataframe The CAN Mailbox The CAN API Polling vs. Interrupts Transmit Dataframes Polling vs. Interrupt Receive Dataframes Polling vs. Interrupt Error Handling Lab Application Level Considerations 5

6 Lab Learn how to Initialize the CAN peripheral with the API Transmit from a CAN mailbox Receive data to a mailbox Use a low cost CAN Monitor to view and send CAN dataframes The CAN API The lab is straightforward Reading Understanding Uncommenting code So don t leave! 6

7 Where CAN is Best! 4 min. Mainly on-board comm. Poor noise immunity Too expensive 7

8 CAN Continuously Moving into New Fields Machines (knitting) Agriculture Control Electronics Factory Assembly Lines Medical Systems Railway Electronics Marine Electronics Elevators Building Automation Printing, Copying 8

9 Lowest Levels Dataframe and Mailbox 9

10 The Dataframe Standard 11-bit ID Dataframe S O F Identifier Rem Req ID extend Control Data (Bytes) C R C A C K I F S bytes Application software only reads/writes CAN ID Data Length Code (in Control Field) Data Field 10

11 Frame Resides in Mailbox Mailbox A.k.a. Message Box, Buffer, Slot Application <-> Bus point of interaction One mailbox handles one complete dataframe (0-8 bytes) RX has 32 mailboxes/peripheral With two channels, 64 mailboxes to use on one bus More mailboxes SW design easier More SW design flexibility Less runtime reconfiguring 11

12 Managing a Mailbox Field Transmit Receive Setup mailbox Receive Get message ID DLC Write Write Write - Read Read All app needs to do! Data Write - Read HW takes care of rest Tx mailbox: HW takes care of low level transmit details Rx mailbox: HW captures messages with the set ID Mailboxes can be reconfigured at runtime 12

13 CAN Firmware & Peripheral Interaction Node MCU Node MCU Node MCU Configure a mailbox to send a frame with ID=5 Configure a mailbox to receive ID=5 Firmware Mailboxes ID=5,Data=123,TX Mailboxes Mailboxes ID=5,Data= 123,RX CAN Peripheral Mask Mask Mask Transceiver Transceiver Transceiver 13

14 Question Which of these do you need in order to setup a mailbox to transmit? 1. CAN ID 2. Data Length Code 3. Data Field 4. All above Which of these do you need to specify to setup a mailbox to receive? 1. CAN ID 2. Data Length Code 3. Data Field 4. All above 14

15 Application Level 15

16 Layers (Where are we?) Let s move up the layers. Optional industrial protocol 16

17 Dealing with the CAN Registers CAN Initialization START Enter CAN reset/ initialization mode Exit CAN sleep mode CAN reset mode? 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 NO can be tedious. Sure would be nice to have Set CAN bit timing and baud rate Set mask register Go to CAN operation mode CAN operation mode? YES END NO The CAN API 17

18 The CAN API 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, CANPORT_RETURN_TO_NORMAL] Send R_CAN_TxSet (ch_nr, mbox_nr, frame_p, frame_type); R_CAN_Tx (ch_nr, mbox_nr); R_CAN_TxCheck (ch_nr, mbox_nr); R_CAN_TxStopMsg (ch_nr, mbox_nr); The CAN API Receive 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); R_CAN_RxSetMask (ch_nr, sid_mask_value, mask_reg_nr); Error Check R_CAN_CheckErr (ch_nr); 18

19 Polling vs. Interrupts 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 Interrupts For processing data as soon as it arrives When messages may not be lost - linked messages To avoid overwrite / overrun 19

20 Transmitting A Frame struct can_std_data_s { uint16 id; uint8 dlc; uint8 data[8]; }; struct can_std_frame_t my_tx_frame.id = 0x700; my_tx_frame.dlc = 2; my_tx_frame.data[0] = 0x11; my_tx_frame.data[1] = 0x22; my_tx_frame; The CAN API R_CAN_TxSet (0, mbox_nr, &my_tx_frame, DATA_FRAME); The API function Waits for previous frame to finish transmit Clears message control register Disables interrupts for mailbox Sets CAN ID Sets DLC Sets transmit data Transmits Dataframe 20

21 Transmit Verification Not necessary... unless application must know whether message sent yet Example; message in a sequence CAN peripheral will deliver unless Bus Off Just continuously check for Error Passive/Bus Off 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 #define USE_CAN_POLL 0 Successful Dataframe transmit triggers ISR CAN0_TXM0_ISR() checks which mailbox sent. Flag the application that data has been sent! 21

22 Question A CAN mailbox configured with an ID can later be reused to handle other IDs? A. True, a mailbox can be reconfigured at runtime. Can a mailbox be reconfigured from transmit to receive? A. Again, yes! A mailbox can be reconfigured at runtime. 22

23 Configure Mailbox to Receive R_CAN_RxSet(ch_nr, mbox_nr, stid, frame_type); The CAN API The API Waits for any previous transmission/reception to complete Interrupt disables the mailbox Clears mailbox control register Sets Standard ID for selected mailbox Sets Dataframe/Remote frame Sets receive interrupt enabled unless USE_CAN_POLL defined 23

24 Polling for Received Data How to receive Dataframe in application At System Setup In config_r_can_rapi.h #define USE_CAN_POLL 1 When polling from app, use R_CAN_RxPoll(ch_nr, mbox_nr, frame_p); If this returns API_OK, mailbox has new message, call R_CAN_RxRead (ch_nr, mbox_nr, frame_p); Copies data to address -> frame_p. 24

25 Using the Receive Interrupt How to receive Dataframe in application At System Setup In config_r_can_rapi.h #define USE_CAN_POLL 0 When frame arrives with ID set by API the CAN Receive ISR triggers Check which mailbox caused the interrupt with 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 25

26 Lab Setup U A R T J-Link Debug 5V DC Not necessary. CAN only needs V A to mini-b USB cable To PC for J-Link debug SW3 SW2 SW1 LCD YRDK63N CAN Hi = thick red wire -> pin 1 J8 Ring of LEDs v A to B USB cable To PC for Sys Tec CAN monitor SYSTEC CAN bus monitor v 27

27 Application Level Considerations 28

28 Your CAN Application - Keep in Mind No real addresses Messages broadcast to whomever happens to listen! Subdivide ID field for higher level functionality 11-bit ID split into user protocol fields Group priority (critical, info,..) Function ID (temp sensor, motor,..) Device address You CAN use! 29

29 Error Handling Check node state regularly with uint8_t R_CAN_CheckErr(void) The CAN API Returns STATE_ERROR (Error Active): < 127 CAN transmit and receive errors occurred, OK! STATE_ERROR_PASSIVE: Over 127 errors occurred 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. 30

30 Minimum Application Handling of Bus Off Normal application activity Poll if peripheral is in Bus Off Peripheral recovered: Bus Off reached Reinitialize CAN! Application can not send or receive System goes into error mode: Poll if peripheral recovers 31

31 Questions? 32

32 Connect to the Smart Society with CAN! Smart Society Challenge You don t have time to write and debug a reliable CAN driver You need to get your idea to market SOON Solution Use CAN and the CAN API! The CAN API handles controlling the peripheral The CAN peripheral - Handles ALL the low level details Focus on your application! Do you agree? 33

33 Renesas Electronics America Inc.