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


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.


Zoom in



/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;


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:



#define DEVICE_ID_LENGTH       24


#include "objects.h"


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.


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


RevisionDateWhoCommit message
30:65c8d1465863 2017-05-28 hudakz Updated. default tip
29:9ae558ec888c 2017-03-14 hudakz Comments upated.
28:dde6c4aef759 2017-03-11 hudakz Updated.
27:50dcf8aea3ee 2017-03-08 hudakz Updated.
26:f71400b1fa56 2017-03-08 hudakz Updated.
25:1d0488a03905 2017-03-08 hudakz Updated.
24:e2907bcba75e 2017-03-07 hudakz Updated.
23:069287e799cd 2017-03-07 hudakz Updated.
22:f4682a5ddda6 2016-12-01 hudakz Serial communication for STM32F103CT6 boards fixed.
21:7120a0dcc8ee 2016-12-01 hudakz CAN bus frequency for STM32F103C8T6 board corrected.
20:eb1a8042605e 2016-08-16 hudakz Updated.
19:872e304d7e17 2016-08-13 hudakz Updated.
18:22977a898fe9 2016-08-11 hudakz Updated.
17:18d4d0ff26a6 2016-08-10 hudakz CAN and CANMessage moved to CANnucleo namespace.
16:a86f339d1c25 2016-07-31 hudakz Reverted to use CANnucleo library and mbed rev. 120
15:6449443e2207 2016-07-29 hudakz Updated
14:e12ebd1260b1 2016-07-27 hudakz Updated
13:e741def3e4ff 2016-07-27 hudakz Modified to use CAN support built into the mbed library.
12:e91e44924194 2016-07-23 hudakz Updated
11:07d927da1a94 2016-03-11 hudakz Updated.
10:66da8731bdb6 2016-03-11 hudakz Updated.
9:8352cfe17ab1 2015-12-23 hudakz Updated.
8:5bf676c35a8f 2015-12-22 hudakz Support for NUCLEO-F302R8, NUCLEO-F303K8, NUCLEO-F334R8 and DISCO-F334C8 added.
7:2dce8ed51091 2015-12-22 hudakz Support for NUCLEO-F303RE added.
6:7ff95ce72f6d 2015-12-05 hudakz Updated for STM32F103C8T6 boards.
5:c6503b7ae971 2015-10-23 hudakz Updated
4:ccf4ac2deac8 2015-07-25 hudakz updated
3:464b06c16d24 2015-07-24 hudakz bug in setting LED status fixed
2:49c9430860d1 2015-07-23 hudakz updated
1:267d6288df33 2015-07-19 hudakz rev 01
0:c5e5d0df6f2a 2015-07-19 hudakz rev 00