Using CAN bus with NUCLEO boards (Demo for the CANnucleo library).

Dependencies:   CANnucleo mbed-dev

Dependents:   BMS_2 Can_sniffer_BMS_GER Can_sniffer_bms ECU_1

Using CAN bus with NUCLEO boards

Demo for the CANnucleo library


Information

Because CAN support has been finally implemented into the mbed library also for the STM boards there is no need to use the CANnucleo library anymore (however you may if you want). See the CAN_Hello example which is trying to demonstrate the mbed built-in CAN API using NUCLEO boards.

Two low cost STM32F103C8T6 boards are connected to the same CAN bus via transceivers (MCP2551 or TJA1040, or etc.). CAN transceivers are not part of NUCLEO boards, therefore must be added by you. Remember also that CAN bus (even a short one) must be terminated with 120 Ohm resitors at both ends.

Schematic

Zoom in

/media/uploads/hudakz/can_nucleo_hello.png

Hookup

/media/uploads/hudakz/20150724_080148.jpg Zoom in

The mbed boards in this example are transmitting CAN messages carrying two data items:

uint8_t   counter;  // one byte
float     voltage;  // four bytes

So in this case the total length of payload data is five bytes (must not exceed eight bytes).
For our convenience, the "<<" (append) operator is used to add data to the CAN message.
The usage of "<<" and ">>" operators is similar to the C++ io-streams operators. We can append data one at a time

txMsg << counter;
txMsg << voltage;

or combine all into one expression.

txMsg << counter << voltage;

The actual data length of a CAN message is automatically updated when using "<<" or ">>" operators.
After successful transmission the CAN message is printed to the serial terminal of the connected PC. So we can check the details (ID, type, format, length and raw data). If something goes wrong during transmission a "Transmission error" message is printed to the serial terminal.

On arrival of a CAN message it's also printed to the serial terminal of the connected PC. So we can see the details (ID, type, format, length and raw data). Then its ID is checked. If there is a match with the ID of awaited message then data is extracted from the CAN message (in the same sequence as it was appended before transmitting) using the ">>" (extract) operator one at a time

rxMsg >> counter;
rxMsg >> voltage;

or all in one shot

rxMsg >> counter >> voltage;

Important

Before compiling the project, in the mbed-dev library open the device.h file associated with the selected target board and add #undef DEVICE_CAN as follows:

device.h

#ifndef MBED_DEVICE_H
#define MBED_DEVICE_H

//=======================================
#define DEVICE_ID_LENGTH       24

#undef DEVICE_CAN

#include "objects.h"

#endif

NOTE: Failing to do so will result in compilation errors.

The same source code is used for both boards, but:

  • For board #1 compile the example without any change to main.cpp
  • For board #2 comment out the line #define BOARD1 1 before compiling

Once binaries have been downloaded to the boards, reset board #1.

NOTE:

The code published here was written for the official NUCLEO boards. When using STM32F103C8T6 boards, shown in the picture above (LED1 is connected to pin PC_13 and, via a resistor, to +3.3V),

  • Import the mbed-STM32F103C8T6 library into your project.
  • Include (uncomment) the line #define TARGET_STM32F103C8T6 1
  • Select NUCLEO-F103RB as target platform for the online compiler.

CAN bus related information

Committer:
hudakz
Date:
Sun Jul 19 09:09:42 2015 +0000
Revision:
0:c5e5d0df6f2a
Child:
1:267d6288df33
rev 00

Who changed what in which revision?

UserRevisionLine numberNew contents of line
hudakz 0:c5e5d0df6f2a 1 /*
hudakz 0:c5e5d0df6f2a 2 * An example showing how to use the CANnucleo library:
hudakz 0:c5e5d0df6f2a 3 *
hudakz 0:c5e5d0df6f2a 4 * Two NUCLEO boards are connected to the same CAN bus via CAN transceivers (MPC2551 or TJA1040, or etc.).
hudakz 0:c5e5d0df6f2a 5 * Transceivers are not part of the NUCLEO boards, therefore must be added by you.
hudakz 0:c5e5d0df6f2a 6 * Remember also that CAN bus must be terminated with 120 Ohm resitors on both ends.
hudakz 0:c5e5d0df6f2a 7 * See <https://developer.mbed.org/users/WiredHome/notebook/can---getting-started/>
hudakz 0:c5e5d0df6f2a 8 * The same source code is used for both NUCLEO boards, but:
hudakz 0:c5e5d0df6f2a 9 * For board #1 compile the example without any change.
hudakz 0:c5e5d0df6f2a 10 * For board #2 set BOARD1 to 0
hudakz 0:c5e5d0df6f2a 11 *
hudakz 0:c5e5d0df6f2a 12 * Note:
hudakz 0:c5e5d0df6f2a 13 * To simplify adding/getting data to/from a CAN message
hudakz 0:c5e5d0df6f2a 14 * inserter "<<" and extractor ">>" operators have been defined.
hudakz 0:c5e5d0df6f2a 15 * Please be aware that CAN message maximum data length is limited to eight bytes.
hudakz 0:c5e5d0df6f2a 16 * To make sure this limitation is not violated I recommend to first compile
hudakz 0:c5e5d0df6f2a 17 * your application with DEBUG enabled in "CAN.h" file.
hudakz 0:c5e5d0df6f2a 18 * Then run it and check for error messages.
hudakz 0:c5e5d0df6f2a 19 */
hudakz 0:c5e5d0df6f2a 20
hudakz 0:c5e5d0df6f2a 21 #include "mbed.h"
hudakz 0:c5e5d0df6f2a 22 #include "CAN.h"
hudakz 0:c5e5d0df6f2a 23
hudakz 0:c5e5d0df6f2a 24 #define BOARD1 1 // please change to 0 when compiling for board #2
hudakz 0:c5e5d0df6f2a 25
hudakz 0:c5e5d0df6f2a 26 #if defined(BOARD1)
hudakz 0:c5e5d0df6f2a 27 #define RX_ID 0x100
hudakz 0:c5e5d0df6f2a 28 #define TX_ID 0x101
hudakz 0:c5e5d0df6f2a 29 #else
hudakz 0:c5e5d0df6f2a 30 #define RX_ID 0x101
hudakz 0:c5e5d0df6f2a 31 #define TX_ID 0x100
hudakz 0:c5e5d0df6f2a 32 #endif
hudakz 0:c5e5d0df6f2a 33
hudakz 0:c5e5d0df6f2a 34 DigitalOut led(LED1);
hudakz 0:c5e5d0df6f2a 35 Timer timer;
hudakz 0:c5e5d0df6f2a 36 CAN can(PA_11, PA_12); // rx, tx
hudakz 0:c5e5d0df6f2a 37 CANMessage rxMsg;
hudakz 0:c5e5d0df6f2a 38 CANMessage txMsg;
hudakz 0:c5e5d0df6f2a 39 long int counter;
hudakz 0:c5e5d0df6f2a 40 volatile bool msgAvailable = false;
hudakz 0:c5e5d0df6f2a 41
hudakz 0:c5e5d0df6f2a 42 /**
hudakz 0:c5e5d0df6f2a 43 * @brief 'CAN receive-complete' interrup handler.
hudakz 0:c5e5d0df6f2a 44 * @note Called on arrival of new CAN message.
hudakz 0:c5e5d0df6f2a 45 * Keep it as short as possible.
hudakz 0:c5e5d0df6f2a 46 * @param
hudakz 0:c5e5d0df6f2a 47 * @retval
hudakz 0:c5e5d0df6f2a 48 */
hudakz 0:c5e5d0df6f2a 49 void onMsgReceived() {
hudakz 0:c5e5d0df6f2a 50 msgAvailable = true;
hudakz 0:c5e5d0df6f2a 51 }
hudakz 0:c5e5d0df6f2a 52
hudakz 0:c5e5d0df6f2a 53 /**
hudakz 0:c5e5d0df6f2a 54 * @brief Main
hudakz 0:c5e5d0df6f2a 55 * @note
hudakz 0:c5e5d0df6f2a 56 * @param
hudakz 0:c5e5d0df6f2a 57 * @retval
hudakz 0:c5e5d0df6f2a 58 */
hudakz 0:c5e5d0df6f2a 59 int main() {
hudakz 0:c5e5d0df6f2a 60 can.frequency(500000); // Initialize CAN and set bit rate to 500kbs
hudakz 0:c5e5d0df6f2a 61 can.attach(&onMsgReceived, CAN::RxIrq); // attach 'CAN receive complete' interrupt handler
hudakz 0:c5e5d0df6f2a 62 timer.reset();
hudakz 0:c5e5d0df6f2a 63 #if defined(BOARD1)
hudakz 0:c5e5d0df6f2a 64 led = 1;
hudakz 0:c5e5d0df6f2a 65 timer.start();
hudakz 0:c5e5d0df6f2a 66 #else
hudakz 0:c5e5d0df6f2a 67 led = 0;
hudakz 0:c5e5d0df6f2a 68 #endif
hudakz 0:c5e5d0df6f2a 69
hudakz 0:c5e5d0df6f2a 70 while(1) {
hudakz 0:c5e5d0df6f2a 71 if(timer.read() >= 2.0) { // check for timeout
hudakz 0:c5e5d0df6f2a 72 timer.stop(); // stop timer
hudakz 0:c5e5d0df6f2a 73 timer.reset(); // reset timer (to avaoid repeated send)
hudakz 0:c5e5d0df6f2a 74 counter++; // increment counter
hudakz 0:c5e5d0df6f2a 75 txMsg.clear(); // clear Tx message storage
hudakz 0:c5e5d0df6f2a 76 txMsg.id = TX_ID; // set ID
hudakz 0:c5e5d0df6f2a 77 txMsg << counter; // append first data item (always make sure that CAN message total data lenght <= 8 bytes!)
hudakz 0:c5e5d0df6f2a 78 txMsg << led.read(); // append second data item (always make sure that CAN message total data lenght <= 8 bytes!)
hudakz 0:c5e5d0df6f2a 79 can.write(txMsg); // transmit message
hudakz 0:c5e5d0df6f2a 80 printf("CAN message sent\r\n");
hudakz 0:c5e5d0df6f2a 81 led = 0; // turn off led
hudakz 0:c5e5d0df6f2a 82 }
hudakz 0:c5e5d0df6f2a 83 if(msgAvailable) {
hudakz 0:c5e5d0df6f2a 84 msgAvailable = false; // reset flag for next use
hudakz 0:c5e5d0df6f2a 85 can.read(rxMsg); // read message into Rx message storage
hudakz 0:c5e5d0df6f2a 86 printf("CAN message with ID = %x received\r\n", rxMsg.id);
hudakz 0:c5e5d0df6f2a 87 if(rxMsg.id == RX_ID) { // if ID matches
hudakz 0:c5e5d0df6f2a 88 rxMsg >> counter; // extract first data item
hudakz 0:c5e5d0df6f2a 89 rxMsg >> led; // extract second data item (and set led status)
hudakz 0:c5e5d0df6f2a 90 printf("counter = %d", counter);
hudakz 0:c5e5d0df6f2a 91 timer.start();
hudakz 0:c5e5d0df6f2a 92 }
hudakz 0:c5e5d0df6f2a 93 }
hudakz 0:c5e5d0df6f2a 94 }
hudakz 0:c5e5d0df6f2a 95 }
hudakz 0:c5e5d0df6f2a 96
hudakz 0:c5e5d0df6f2a 97