Hello everyone,
I currently trying to build a CAN interface for Arduino based on this post. I set up two Arduino Nanos with the same setup. The chips are powered over their respective Arduinos. The only connection is GND, CANH, CANL (see picture).
Since the library mentioned in the post did not work, I now use this. It just read/writes the registers more efficiently.
The write-code:
#include <Arduino.h>
#include <mcp2515.h>
struct can_frame canMsg1;
struct can_frame canMsg2;
MCP2515 can(10);
void setup() {
Serial.begin(9600); //to communicate with Serial monitor
SPI.begin();
can.reset();
can.setBitrate(CAN_125KBPS);
can.setNormalMode();
Serial.println("---Setup: Write---");
uint8_t stat = can.getStatus();
Serial.print("status = "); Serial.println(stat);
canMsg1.can_id = 0x0F6;
canMsg1.can_dlc = 8;
canMsg1.data[0] = 0x8E;
canMsg1.data[1] = 0x87;
canMsg1.data[2] = 0x32;
canMsg1.data[3] = 0xFA;
canMsg1.data[4] = 0x26;
canMsg1.data[5] = 0x8E;
canMsg1.data[6] = 0xBE;
canMsg1.data[7] = 0x86;
canMsg2.can_id = 0x036;
canMsg2.can_dlc = 8;
canMsg2.data[0] = 0x0E;
canMsg2.data[1] = 0x00;
canMsg2.data[2] = 0x00;
canMsg2.data[3] = 0x08;
canMsg2.data[4] = 0x01;
canMsg2.data[5] = 0x00;
canMsg2.data[6] = 0x00;
canMsg2.data[7] = 0xA0;
Serial.println("---Setup: End ---");
}
//loading the data bytes of the message. Up to 8 bytes
unsigned char data[8] = {'C', 'a', 'r', 't', 'e', 'r', 'a', '!'};
void loop() {
//CAN.sendMsgBuf(msg ID, extended?, #of data bytes, data array);
can.sendMessage(&canMsg1);
// can.sendMessage(&canMsg2);
Serial.println("write");
delay(2000);
}
the write-Code:
#include <Arduino.h>
#include <mcp2515.h>
struct can_frame canMsg;
MCP2515 can(10);
void setup() {
Serial.begin(9600); //to communicate with Serial monitor
SPI.begin();
can.reset();
can.setBitrate(CAN_125KBPS);
can.setNormalMode();
Serial.println("---Setup: Read---");
uint8_t stat = can.getStatus();
Serial.print("status = "); Serial.println(stat);
Serial.println("---Setup: End ---");
}
//loading the data bytes of the message. Up to 8 bytes
unsigned char data[8] = {'C', 'a', 'r', 't', 'e', 'r', 'a', '!'};
void loop() {
//CAN.sendMsgBuf(msg ID, extended?, #of data bytes, data array);
if (can.readMessage(&canMsg) == MCP2515::ERROR_OK) {
Serial.print("ID:");
Serial.print(canMsg.can_id, HEX); // print ID
Serial.print("\t");
Serial.print("DLC:");
Serial.print(canMsg.can_dlc, HEX); // print DLC
Serial.print("\t");
Serial.print("DAT:");
for (int i = 0; i<canMsg.can_dlc; i++) { // print the data
Serial.print(canMsg.data[i],HEX);
Serial.print(" ");
}
Serial.println();
}
}
The output reads
ID:9FFFFF80 DLC:0 DAT:
ID:400 DLC:0 DAT:
ID:0 DLC:0 DAT:
ID:9FFFFF00 DLC:0 DAT:
ID:0 DLC:8 DAT:0 0 0 0 0 0 F0 F8
ID:9FFFFFFF DLC:8 DAT:FE F8 E0 E0 C0 E0 F0 E0
ID:40000000 DLC:0 DAT:
ID:9FFF0000 DLC:0 DAT:
ID:DFDFFEFC DLC:8 DAT:FE FE FF FE F8 F8 F0 F0
but even if I send every 2000ms the messages do not come through every time and even if it does the messages are not the same.
I measured the some signals with my osci. The clock, the SPI communication (from Nano to MCP2515) and the power level seem right. The outputs of RX,TX of the MCP2515 to the MCP2551 shows somekind of signal, but I do not know how this communication should look like (probably with the same bitstream as the SPI). Also the Signal from CANH and CANL show not the original message (based on the standard CAN frame protocol).
Does anyone has experience with CAN communication using MCP2515 and a transceiver?
The only difference between my custom setup and a commercial shield is, that the breadboard setup has a lot of long cables and everything is very noisy and not as clean as on a PCB.
