Can bus adapter linux

How to configure and use CAN bus

This article explains how to enable the CAN bus using as examples the AM35x EVM and OMAP35x, but can be applied to other platforms as well. In addition, steps to exchange data with a MCP2515 Bus Monitor board is also documented.

If you are new to CAN, please spend 15 minutes reading the CAN bus protocol technical overview.

Contents

• 1 References
• 2 Enable the CAN controller kernel driver
  • 2.1 AM35x kernel
  • 2.2 OMAP3x kernel
  • 5.1 Linux boot
  • 5.2 sysfs entries
    • 5.2.1 MC2515
    • 10.1 MCP251x Platform Bus Data
    • 10.2 GPIO MCP251x interrupt verification
    • 11.1 No can0 interface
    • 11.2 bit-timing calculation not available
    • 11.3 bit-timing not yet defined
    • 11.4 MCP251x didn’t wake-up
    • 11.5 ip command says link/[280] instead of link/can
    • 11.6 NOHZ: local_softirq_pending 08
    • 12.1 Files
    • 12.2 Commands Examples

    References

    Enable the CAN controller kernel driver

    AM35x kernel

    In the case of the AM35x platform the configuration is:

    Linux Kernel Configuration Networking support CAN bus subsystem support CAN device drivers Platform CAN drivers with Netlink support CAN bit-timing calculation TI High End CAN controller (HECC)

    OMAP3x kernel

    In the case of the OMAP3x platform with a MCP2515 chip the configuration is:

    Linux Kernel Configuration Networking support CAN bus subsystem support CAN device drivers Platform CAN drivers with Netlink support CAN bit-timing calculation Microchip MCP251x SPI CAN controller

    Enable socketcan and ip tools

    Working with the CAN bus requires enabling the ‘ip’ tools from iproute2 package (the ‘ip’ tool from busybox won’t work). The socketcan package is optional and provide you with tools to debug your can bus.

    These packages are available for selection from the RidgeRun SDK in the configuration menu.

    File System Configuration Select target's file system software iproute2-2.6.34 socketcan utils

    Setup the networking rules

    Edit your /etc/networking/interfaces on the target file system and add the following rules (required to setup the bit-rate of the bus):

    auto can0 iface can0 inet manual #pre-up ip link set $IFACE type can bitrate 125000 listen-only off pre-up /sbin/ip link set $IFACE type can bitrate 125000 triple-sampling on up /sbin/ifconfig $IFACE up down /sbin/ifconfig $IFACE down

    Verifying CAN support configuration

    Linux boot

    Look for the following in the Linux boot output

    mcp251x spi1.0: setup: speed 750000, sample leading edge, clk normal mcp251x spi1.0: setup mode 0, 8 bits/w, 1000000 Hz max --> 0 mcp251x spi1.0: CANSTAT 0x80 CANCTRL 0x07 mcp251x spi1.0: probed

    PM: Adding info for No Bus:can0 CAN device driver interface can: controller area network core (rev 20090105 abi 8)

    sysfs entries

    Verify the CAN host driver is registered correctly (meaning properly added to kernel arch/arm/mach-*/board-*.c file).

    MC2515

    ls -d /sys/bus/spi/drivers/mcp251x cat /sys/devices/platform/omap2_mcspi.1/spi1.0/modalias ls /sys/class/net/

    /sys/bus/spi/drivers/mcp251x mcp2515 can0 eth0 lo

    Power on CAN hardware

    ip link set can0 type can bitrate 125000 triple-sampling on ifconfig can0 up

    Send simple test packet

    The socket-CAN tools include the cansend utility:

    where the device is the network interface name, typically can0, and a CAN frame is in the format:

    with the can_id having 3 (SFF) or 8 (EFF) hex chars. and data in the format of zero to eight 8-bit hex-values that can optionally be separated by a period (‘.’) or use R for remote transmission request.

    To send a CAN data frame message, with a can_id arbitration field value of 0x5A1 and a data field value 0x1122334455667788:

    cansend can0 5A1#11.22.33.44.55.66.77.88

    If you are using a CAN bus monitor, like the MCP2515 bus monitor, You will see (packet sent 3 times):

    

    Dump received packets

    The socket-CAN tools include the candump utility, which dumps all messages being exchanged on the CAN bus. To run candump, just specify the CAN interface:

    If a device on the CAN bus sends a packet with ID 0x456 and data 0x122345, the output would be

    # candump can0 can0 456 [3] 12 23 45

    The MCP2515 bus monitor allows you to send CAN bus packet. You can also telnet into the target hardware and use cansend to put a packet on the bus that can be monitiored with candump.

    cansend can0 5A1#11.22.33.44.55.66.77.88

    creates the following cumulative candump output

    / # candump can0 can0 456 [3] 12 23 45 can0 5A1 [8] 11 22 33 44 55 66 77 88

    CAN protocol stack information

    The CAN protocol implementation version:

    MCP251x interrupt signal

    MCP251x Platform Bus Data

    In the architecture specific board file, such as arch/arm/mach-omap2/board-overo.c, first define the platform data:

    #include static int overo_mcp2515_setup(struct spi_device *sdev) < printk(KERN_DEBUG "overo_mcp2515_setup: Entry\n"); return 0; >static int overo_mcp2515_transceiver_enable(int enable) < printk(KERN_DEBUG "overo_mcp2515_transceiver_enable: Entry %d\n", enable); return 0; >static struct mcp251x_platform_data overo_mcp2515_pdata = < .oscillator_frequency = 32*1000*1000, .board_specific_setup = overo_mcp2515_setup, .model = CAN_MCP251X_MCP2515, .power_enable = overo_mcp2515_transceiver_enable, >; 
    Then add the logic to initialize the GPIO used as the incoming mcp251x interrupt signal: 
    static void __init overo_mcp251x_init(void) < printk(KERN_DEBUG "overo_mcp251x_init: Entry\n"); if ((gpio_request(OVERO_GPIO_CAN_INT, "MCP251x CAN INT") == 0) && (gpio_direction_input(OVERO_GPIO_CAN_INT) == 0)) < gpio_export(OVERO_GPIO_CAN_INT, 0); set_irq_type(OMAP_GPIO_IRQ(OVERO_GPIO_CAN_INT), IRQ_TYPE_EDGE_FALLING); >else < printk(KERN_ERR "could not obtain gpio for MCP251x CAN bus interrupt\n"); return; >>
     
    Add the SPI information to the SPI board info array:
     
    Finally call the GPIO interrupt initialization function right before registering SPI board info:
     
    overo_mcp251x_init(); spi_register_board_info(overo_spi_board_info, ARRAY_SIZE(overo_spi_board_info));
     
    GPIO MCP251x interrupt verification
     
    You can use debugfs to monitor the GPIO used for the MCP251x interrupt signal.
     
    Configure the kernel to enable debugfs:
     
    Symbol: DEBUG_FS [=y] Prompt: Debug Filesystem Defined at lib/Kconfig.debug:77 Depends on: SYSFS Location: -> Kernel configuration -> Kernel hacking
     
    Boot the target hardware and mount debugfs:
     
    mount -t debugfs none /sys/kernel/debug
     
    Check the current value and configuration for the GPIO of interest (for example GPIO 147):
     
    fgrep 147 /sys/kernel/debug/gpio
     
    with example output being:
     
    gpio-147 (MCP251x CAN INT) in hi irq-274 edge-falling
     
    Which indicates GPIO 147 is configure as an input, currently has a high logic level, is mapped to IRQ 307, and causes an interrupt on the falling edge.
     
    You can see if any interrupts have occurred using (for example GPIO 147 being mapped to IRQ 307):
     
    with example output being:
     
    which indicates 60 interrupts have been occurred.
     
    With OMAP3, you also need to verify the pad where the signal leaves the chip is configured properly. For the OMAP3 in the CBB package (used on Gumstix Overo Water board) GPIO147 uses the uart2_rx pad.
     
    cat /sys/kernel/debug/omap_mux/uart2_rx
     
    with example output being:
     
    name: uart2_rx.gpio_147 (0x4800217a/0x14a = 0x4104), b ad25, t NA mode: OMAP_PIN_INPUT | OMAP_PIN_OFF_WAKEUPENABLE | OMAP_MUX_MODE4 signals: uart2_rx | mcbsp3_fsx | gpt8_pwm_evt | NA | gpio_147 | NA | NA | safe_mode
     
    Problems and how to resolve them
     
    The titles of the following sections are text that gets displayed when a problem occurs. Each section describes how to resolve the issue.
     
    No can0 interface
     
    If you have problems with network interface can0 not being created, enable
     
    kernel -> Device Drivers -> Generic Driver Options -> Driver Core verbose debug messages
     
    kernel -> Networking support -> CAN bus subsystem support -> CAN Device Drivers -> CAN devices debugging messages
     
    bit-timing calculation not available
     
    Enable CAN bit-timing calculation in the Linux kernel.
     
    kernel -> Networking support -> CAN bus subsystem support -> CAN Device Drivers -> CAN bit-timing calculation
     
    bit-timing not yet defined
     
    ip link set can0 type can bitrate 125000 triple-sampling on
     
    MCP251x didn't wake-up
     
    If the response to ifconfig can0 up is
     
    mcp251x spi1.0: MCP251x didn't wake-up mcp251x spi1.0: CNF: 0x03 0xf5 0x01
     
    Then there is a problem with the interrupt signal from the MCP251x chip back to the driver. Check the arch/arm/mach-*/board-*.c file for your hardware along with any jumpers on your hardware design.
     
    ip command says link/[280] instead of link/can
     
    You need to enable and build iproute2 to get an up-to-date ip command that supports the can bus.
     
    NOHZ: local_softirq_pending 08
     
    You are using an older version of the mcp2515 driver. The driver should call netif_rx() only from interrupt context. Update to a newer version of the driver and the warning will go away.
     
    System files and command
     
    Files
     
    Commands Examples
     
    ip -details link show can0
     
    Источник
     
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    CANBus-MQTT Adapter for connecting your car to the Internet of Things
     
    ClearBlade/CANBus-Adapter
     
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    README.md 
     
    CAN Bus Adapter allows an automotive's CAN (Controller Area Network) Bus to publish MQTT messages.
     
    sudo apt-get install libssl-dev libcurl4-openssl-dev libjansson-dev gcc autoconf libtool 
     
    git clone https://github.com/eclipse/paho.mqtt.c.git cd paho.mqtt.c make clean make sudo make install 
     
    git clone https://github.com/ClearBlade/ClearBlade-C-SDK cd ClearBlade-C-SDK make clean make sudo make install 
     
    #ifndef _CONSTANTS_H #define _CONSTANTS_H char *SYSTEM_KEY = ; // ex. "94aaa4890bc0afe1fbd282b1ac8e01" char *SYSTEM_SECRET = ; // ex. "9AAEC4890BC68AB6B9BBEDF6B21F" char *USER_EMAIL = ; // ex. "test@clearblade.com" char *USER_PASSWORD = ; // ex. "password" . #endif 
     
    cd /path/to/canbus-adapter/adapters/ make clean make 
     
    git clone https://github.com/linux-can/can-utils cd can-utils ./autogen.sh ./configure make sudo make install 
     
    sudo modprobe can sudo modprobe can_raw sudo modprobe vcan sudo ip link add dev vcan0 type vcan sudo ip link set up vcan0 sudo ip link show vcan0 
     
    sudo ifconfig vcan0 up cansend vcan0 123#1122334455667788 
     
    ClearBlade init successful: NByVFwfSCjVf4zF8XSMTG_osxg3B0BA_Tw-CkqU89jsqSlS_eosLT3pPbc4w1Z0KvTQCWjeSvLnGgxoqQw== Successful connection to MQTT broker Subscribe succeeded vcan0 at index 0 Received data from CAN bus: "3DUfw� Send MQTT message: ID: 291, Data: "3DUfw� 
     
    About
     
    CANBus-MQTT Adapter for connecting your car to the Internet of Things
     
    Источник
     
    CAN Bus
     
    The CAN bus is an ISO standard bus originally developed for vehicles. It manages the Chassis Electrical System Control and is responsible for critical activities like engine electrical, and skid control. This system is also used to provide vehicle diagnostic information for maintenance. A multi-star configuration seems typical of this bus with a primary bus line that branches into sub bus lines at its extremities then attaches to multiple device nodes. Differential voltage is applied over twisted pair at 1.5 to 2.5V and 2.5 to 3.5V for noise resistant signaling. Bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Decreasing the bit rate allows longer network distances (e.g., 500 m at 125 kbit/s). (Jeremiah J. Flerchinger Source) Controllers supporting CAN FD, an enhanced CAN version with frames up to 64 byte and bit rates up to 4 Mbit/s, will be available in the second half of 2014. A can4linux version supportig CAN FD on a IFI CAN is ready to be used.
     
    Although developed as car communication network CAN is used in many other areas, industrial, medical, maritime laboratory and more. Most often with a CAN based higher layer protocol like CANopen on top of it.
     
    Additional information can be found at:
     
    CAN Support in Linux
     
    CAN is supported by Linux device drivers. Mainly two types exist. Character device based drivers and network socket based drivers. The Linux kernel supports CAN with the SocketCAN framework.
     
    One of the character based drivers is can4linux.
     
    SocketCAN Supported Protocols
     
     
    RAW: send & receive raw CAN frames
     
    BCM: Broadcast manager, offload repetitive work to the Linux kernel
     
    ISOTP .
     
    SAE J1939
     
     
    SocketCAN Supported Controllers
     
     
    Microchip MCP251x
     
    Atmel AT91 SoCs
     
    ESD 331 CAN Cards
     
    NXP (Philips) SJA1000
     
    Freescale MPC52xx SoCs
     
    Bosch CC770
     
    Intel AN82527
     
    TIs SoCs
     
    Serial/network devices utilizing ASCII protocol (slcan driver)
     
     
    Источник
     
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