Narrab

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10 years, 10 months ago.

Can Extended

I am a NOOB to CAN and would like to read j1939 Can bus data. This I think is 29bit format at 250kbs. How do you set the Can API up to read CanExtended?

Thanks.

1 Answer

David Smart
10 years, 10 months ago.

Hi Narrab ,

The first place to start, if you haven't already read it in detail, is Handbook - CAN.

The read() method can fill in a CANMessage, The CANMessage has a CANFormat element, which can be "CANStandard" (11-bit) or "CANExtended" (29-bit).

So, you can filter by the message format when you extract it. If you want the CAN controller to only pass 29-bit messages to your application, you may be able to configure that at the register level - but there is not a ready-made high level API for that.

Accepted Answer

Here how you can read and write: .

  1. include "mbed.h"
  2. include "C12832.h"

C12832 lcd(p5, p7, p6, p8, p11);

Ticker ticker; DigitalOut led1(LED1); DigitalOut led2(LED2); DigitalOut led3(LED3); DigitalOut led4(LED4); AnalogIn Pot1(p19); AnalogIn Pot2(p20); DigitalIn fire(p14);

DigitalIn up(p15); DigitalIn rigth(p16); DigitalIn left(p13); DigitalIn down(p12);

CAN can1(p9, p10); CAN can2(p30, p29);

Serial pc(USBTX, USBRX); tx, rx

Timer t; Timeout flipper;

char mensaje[8]; char counter = 0;

void send() {

uint32_t id=0x18FEF320; CANMessage messageOut;

led1 = 1; for (int i=0; i<8; i++) messageOut.data[i]=rand()%255;

create the message

messageOut.format = CANExtended; standard or extended ID (can be skipped for standard) messageOut.id = id; messageOut.len = 8;

if(can2.write(CANMessage(messageOut))) { printf("Id: %x",id); printf(" Sent: "); for(int i = 0; i<8; i++) { if(mensaje[i]<0x10) printf("0"); printf("%x",mensaje[i]); printf(" "); } } else{ printf("Failed to send the message\n\r"); } printf(": >%f\n\r", t.read()); led1 = 0; }

void flip() { led4 = 1; }

int main() { can2.reset(); reset the bus controller pc.baud(115200); t.start(); flipper.attach(&flip, 5.0); setup flipper to call flip after 5 seconds lcd.cls(); lcd.invert(0); 1 lo invierte can1.frequency(250000); can2.frequency(250000); ticker.attach(&send, 1); Calls the function send() every 1 second CANMessage msg;

while(1) {

lcd.set_contrast((Pot2.read_u16()>>10)); set contrast

if(can2.read(msg)) { led4=0; led2 = 1; flipper.detach(); setup flipper to call flip after 2 seconds printf("ID: %x LEN: %x ", msg.id, msg.len); lcd.printf("%0.4x ", msg.id);

for (int i = 0; i < (int)msg.len; i++) { printf("%0.2x ", msg.data[i]); lcd.printf("%0.2x.", msg.data[i]); } lcd.printf("\n\r"); printf("\n\r");

flipper.attach(&flip, 5.0); setup flipper to call flip after 2 seconds } wait(0.2); led2 = 0; indicador de recepción

} }

posted by GERMAN GOMEZ 30 Mar 2016