CAN bus demo MCP25020

This page is related with the DEMOS_MCP25020 package. This software show how to communicate easily on a CAN bus, particularly with the Microchip MCP25020 I/O Expander. This ship is used on the Microchip kit MCP2515DM-PCTL: http://fr.farnell.com/microchip/mcp2515dm-pctl/kit-d-eval-mcp2515-controleur-can/dp/1332096

Warning: Please ensure that you use the trunk version of armadeus (kernel linux-2.6.38.1 is required) before trying the instructions described on this page!

Driver installation

 $ make linux26-menuconfig

Networking support  --->
    <M>   CAN bus subsystem support ---> 
        --- CAN bus subsystem support
        <M>   Raw CAN Protocol (raw access with CAN-ID filtering)
        <M>   Broadcast Manager CAN Protocol (with content filtering)
              CAN Device Drivers  --->
                  <M> Virtual Local CAN Interface (vcan)
                  <M> Platform CAN drivers with Netlink support
                  [*]   CAN bit-timing calculation   
                  <M> Microchip 251x series SPI CAN Controller

 $ make-linux26

• Reflash kernel

Software installation

 $ make menuconfig

    Package Selection for the target  --->
        Armadeus specific tools/utilities  --->
            [*] Armadeus misc demos
            Choose the demos to install  --->
                [*] DEMOS_MCP25020

 $ make

• Reflash rootfs

Mounting

First and foremost, you have to create the bus with the two nodes.

• Add the APF27 as the first node:
  • The pin to connect your APF27-Dev to the CAN bus is on the J13 connector.

J13 - Pins	Functionnalities
1	+3V3
2	CAN H
3	CAN L
4	GND

Check that the J11 is closed on your APF27-Dev board, it will add the end line 120ohm resistor of the CAN bus.

• Add the Microchip kit MCP2515DM-PCTL ( Expander side ) to the CAN bus:

J3 - Pins	Functionnalities
1	nc
2	GND
3	CAN L
4	CAN H
5	GND
6	nc
7	nc
8	+5V
9	nc
10	nc

Check that the JP3 is closed on the Microchip demo board, it will add the end line 120ohm resistor of the CAN bus.

• Connect CAN L, CAN H and GND to the correct pins of the APF27 board

Usage

Once your pins are correctly connected, launch your APF27-Dev Board. With the demonstration program, you can:

• Listen on the bus

 # mcp25020_ctrl listen

• Flash the D6 Led on the Microchip demo board

 # mcp25020_ctrl led-flash [interval]

Interval is 10 to 10000 (The flashing interval in ms)

• Turn ON or OFF the D6 Led on the Microchip demo board

 # mcp25020_ctrl led-state [ON|OFF]

Select ON or OFF to changing the led state.

• Get the state of the SW2 switch on the Microchip demo board (released or pushed)

 # mcp25020_ctrl sw2-get

• Get the status of MCP25020 configuration registers

 # mcp25020_ctrl config

See the MCP25020 datasheet for more informations

Source code

The program source of the demo is viewable in your ARMadeus repository target/demos/mcp25020_ctrl/mcp25020_ctrl.c

Examples program

To create a program with CAN protocol in C/C++, Python, ... is similar to programming a TCP/IP protocol application. Both implement the UNIX socket. You can found some examples in the directory "test" of the socketcan sources, you can found them on:

• http://svn.berlios.de/wsvn/socketcan (trunk->test)

Links

• https://www.ridgerun.com/developer/wiki/index.php/How_to_configure_and_use_CAN_bus (How to configure and use CAN bus)
• http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en024094 (MCP2515 CAN PICtail Demo Board)
• http://ww1.microchip.com/downloads/en/DeviceDoc/21664D.pdf (MCP25020 datasheet)
• http://www.kvaser.com/can/protocol/index.htm (CAN introduction)