Zoltan Hudak / CANnucleo_Hello

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

Diff: main.cpp

Revision:
6:7ff95ce72f6d
Parent:
5:c6503b7ae971
Child:
7:2dce8ed51091
--- a/main.cpp	Fri Oct 23 19:54:49 2015 +0000
+++ b/main.cpp	Sat Dec 05 10:20:00 2015 +0000
@@ -1,30 +1,29 @@
 /*
  * An example showing how to use the CANnucleo library:
  *
- * Two NUCLEO boards are connected to the same CAN bus via CAN transceivers (MCP2551 or TJA1040, or etc.).
- * Transceivers are not part of the NUCLEO boards, therefore must be added by you.
- * Remember also that CAN bus must be terminated with 120 Ohm resitors on both ends.
- * See <https://developer.mbed.org/users/WiredHome/notebook/can---getting-started/>
- * The same source code is used for both NUCLEO boards, but:
+ * Two affordable (less than $4 on ebay) STM32F103C8T6 boards (20kB SRAM, 64kB Flash), 
+ * compatible with the NUCLEO-F103RB platform (20kB SRAM, 128kB Flash), 
+ * 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.
+ *
+ * For more details see the wiki page <https://developer.mbed.org/users/hudakz/code/CAN_Nucleo_Hello/>
+ *
+ * NOTE: If you'd like to use the official NUCLEO-F103RB boards
+ *       comment out the line #define TARGET_STM32F103C8T6  1
+ *
+ * The same code is used for both NUCLEO boards, but:
  *      For board #1 compile the example without any change.
  *      For board #2 comment out the line #define BOARD1 1 before compiling 
  *
- * Once compiled, download the binaries to the boards. 
- * To start ping/ponging messages reset both boards at the same time.
+ * Once the binaries have been downloaded to the boards reset board #1.
  *
- * Note:
- *  To simplify adding/getting data to/from a CAN message
- *  inserter "<<" and extractor ">>" operators have been defined.
- *  Please be aware that CAN message maximum data length is limited to eight bytes.
- *  To make sure this limitation is not violated I recommend to first compile
- *  your application with DEBUG enabled in "CAN.h" file.
- *  Then run it and check for error messages.
  */ 
 
 #include "mbed.h"
 #include "CAN.h"
 
-#define BOARD1    1     // please comment out this line when compiling for board #2
+#define BOARD1    1                 // comment out this line when compiling for board #2
 
 #if defined(BOARD1)
     #define RX_ID   0x100
@@ -34,7 +33,15 @@
     #define TX_ID   0x100
 #endif
 
-DigitalOut      led(LED1);
+// See wiki page <https://developer.mbed.org/users/hudakz/code/CAN_Nucleo_Hello/>
+#define TARGET_STM32F103C8T6  1     // comment out this line if you'd like to use the official NUCLEO-F103RB boards
+                                    
+#if defined(TARGET_STM32F103C8T6)  
+    DigitalOut  led(PC_13);
+#else
+    DigitalOut  led(LED1);
+#endif
+
 int             ledReceived;
 Timer           timer;
 CAN             can(PA_11, PA_12);  // CAN Rx pin name, CAN Tx pin name, Automatic recovery from bus-off state enabled by default
@@ -63,12 +70,20 @@
 int main() {
     can.frequency(1000000);                     // set bit rate to 1Mbps
     can.attach(&onMsgReceived, CAN::RxIrq);     // attach 'CAN receive-complete' interrupt handler
-    timer.reset();
+    
 #if defined(BOARD1)
-    led = 1;
+    #if defined(TARGET_STM32F103C8T6)
+        led = 0;    // turn LED on
+    #else
+        led = 1;    // turn LED on
+    #endif
     timer.start();
 #else
-    led = 0;
+    #if defined(TARGET_STM32F103C8T6)
+        led = 1;    // turn LED off
+    #else
+        led = 0;    // turn LED off
+    #endif
 #endif
 
     while(1) {
@@ -82,7 +97,12 @@
             txMsg << led.read();                // append second data item (make sure that CAN message total data lenght <= 8 bytes!)
             can.write(txMsg);                   // transmit message
             printf("CAN message sent\r\n");
-            led = 0;                            // turn off LED
+            
+            #if defined(TARGET_STM32F103C8T6)
+                led = 1;                        // turn LED off
+            #else
+                led = 0;                        // turn LED off
+            #endif
         }
         if(msgAvailable) {
             msgAvailable = false;               // reset flag for next use
@@ -106,5 +126,3 @@
         }
     }
 }
-
-