CAN - Handbook

CAN

CAN or Controller-area Network is a bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.

Hello World!

Loopback example

#include "mbed.h"

Ticker ticker;
DigitalOut led1(LED1);
DigitalOut led2(LED2);
CAN can1(p9, p10);
CAN can2(p30, p29);

void send() {
    printf("send()\n");
    char counter = 0;
    if(can1.write(CANMessage(1337, &counter, 1))) {
        printf("wloop()\n");
        counter++;
        printf("Message sent: %d\n", counter);
    } 
    led1 = !led1;
}

int main() {
    printf("main()\n");
    ticker.attach(&send, 1);
    CANMessage msg;
    while(1) {
        printf("loop()\n");
        if(can2.read(msg)) {
            printf("Message received: %d\n", msg.data[0]);
            led2 = !led2;
        } 
        wait(0.2);
    }
}

This example sends from one CAN bus (can1) an counter while it is listen on the other CAN bus (can2) to receive a packet. Each bus controller should be connected to a CAN bus transceiver. These should be connected together at a CAN bus.

API

API summary

CANMessage
Functions
CANMessage	Creates empty CAN message.
CANMessage	Creates CAN message with specific content.
CANMessage	Creates CAN remote message.
Variables
id	The message id.
data	Space for 8 byte payload.
len	Length of data in bytes.
format	Defines if the message has standard or extended format.
type	Defines the type of a message.
CAN	A can bus client, used for communicating with can devices
Functions
CAN	Creates an CAN interface connected to specific pins.
frequency	Set the frequency of the CAN interface
write	Write a CANMessage to the bus.
read	Read a CANMessage from the bus.
reset	Reset CAN interface.
monitor	Puts or removes the CAN interface into silent monitoring mode
rderror	Returns number of read errors to detect read overflow errors.
tderror	Returns number of write errors to detect write overflow errors.
attach	Attach a function to call whenever a CAN frame received interrupt is generated.

class CANMessage : public CAN_Message

CANMessage()

Creates empty CAN message.

unsigned int id

The message id.

unsigned char data[8]

Space for 8 byte payload.

unsigned char len

Length of data in bytes.

CANFormat format

Defines if the message has standard or extended format.

CANType type

Defines the type of a message.

class CAN : public Base

A can bus client, used for communicating with can devices

CAN( PinName rd,
PinName td )

Creates an CAN interface connected to specific pins.

int frequency( int hz )

Set the frequency of the CAN interface

int write( CANMessage msg )

Write a CANMessage to the bus.

int read( CANMessage & msg )

Read a CANMessage from the bus.

void reset()

Reset CAN interface.

void monitor( bool silent )

Puts or removes the CAN interface into silent monitoring mode

unsigned char rderror()

Returns number of read errors to detect read overflow errors.

unsigned char tderror()

Returns number of write errors to detect write overflow errors.

void attach( void (*fptr)(void) )

Attach a function to call whenever a CAN frame received interrupt is generated.

Details

The CAN Interface can be used on mbed pins p9/p19 and p30/p29

The CAN Interface can be used to write data words out of a CAN port and will return the data received from another CAN device. The CAN clock frequency can be configured.

Resources

Wikipedia

Last modified 21 Jul 2010, by Dan Ros

No tags | 1 reply Share:

1 comment on CAN:

Bo Ni

# 2 weeks, 3 days ago

I'm glad so there is one more CAN in mbed, but you could repair that picture :) http://mbed.org/media/uploads/simon/mbedmicrocontrollerpinout4.png There is drawn only one CAN

Please login to post comments.