CAN Controller

Overview
Sending
Receiving
Setting the bitrate
SocketCAN
Samples
API Reference

Overview 

Controller Area Network is a two-wire serial bus specified by the Bosch CAN Specification, Bosch CAN with Flexible Data-Rate specification and the ISO 11898-1:2003 standard. CAN is mostly known for its application in the automotive domain. However, it is also used in home and industrial automation and other products.

A CAN transceiver is an external device that converts the logic level signals from the CAN controller to the bus-levels. The bus lines are called CAN High (CAN H) and CAN Low (CAN L). The transmit wire from the controller to the transceiver is called CAN TX, and the receive wire is called CAN RX. These wires use the logic levels whereas the bus-level is interpreted differentially between CAN H and CAN L. The bus can be either in the recessive (logical one) or dominant (logical zero) state. The recessive state is when both lines, CAN H and CAN L, at roughly at the same voltage level. This state is also the idle state. To write a dominant bit to the bus, open-drain transistors tie CAN H to Vdd and CAN L to ground. The first and last node use a 120-ohm resistor between CAN H and CAN L to terminate the bus. The dominant state always overrides the recessive state. This structure is called a wired-AND.

Warning

CAN controllers can only initialize when the bus is in the idle (recessive) state for at least 11 recessive bits. Therefore you have to make sure that CAN RX is high, at least for a short time. This is also necessary for loopback mode.

The bit-timing as defined in ISO 11898-1:2003 looks as following:

A single bit is split into four segments.

Sync_Seg: The nodes synchronize at the edge of the Sync_Seg. It is always one time quantum in length.
Prop_Seg: The signal propagation delay of the bus and other delays of the transceiver and node.
Phase_Seg1 and Phase_Seg2 :Define the sampling point. The bit is sampled at the end of Phase_Seg1.

The bit-rate is calculated from the time of a time quantum and the values defined above. A bit has the length of Sync_Seg plus Prop_Seg plus Phase_Seg1 plus Phase_Seg2 multiplied by the time of single time quantum. The bit-rate is the inverse of the length of a single bit.

A bit is sampled at the sampling point. The sample point is between Phase_Seg1 and PhaseSeg2 and therefore is a parameter that the user needs to choose. The CiA recommends setting the sample point to 87.5% of the bit.

The resynchronization jump width (SJW) defines the amount of time quantum the sample point can be moved. The sample point is moved when resynchronization is needed.

The timing parameters (SJW, bitrate and sampling point, or bitrate, Prop_Seg, Phase_Seg1and Phase_Seg2) are initially set from the device-tree and can be changed at run-time from the timing-API.

CAN uses so-called identifiers to identify the frame instead of addresses to identify a node. This identifier can either have 11-bit width (Standard or Basic Frame) or 29-bit in case of an Extended Frame. The Zephyr CAN API supports both Standard and Extended identifiers concurrently. A CAN frame starts with a dominant Start Of Frame bit. After that, the identifiers follow. This phase is called the arbitration phase. During the arbitration phase, write collisions are allowed. They resolve by the fact that dominant bits override recessive bits. Nodes monitor the bus and notice when their transmission is being overridden and in case, abort their transmission. This effectively gives lower number identifiers priority over higher number identifiers.

Filters are used to whitelist identifiers that are of interest for the specific node. An identifier that doesn’t match any filter is ignored. Filters can either match exactly or a specified part of the identifier. This method is called masking. As an example, a mask with 11 bits set for standard or 29 bits set for extended identifiers must match perfectly. Bits that are set to zero in the mask are ignored when matching an identifier. Most CAN controllers implement a limited number of filters in hardware. The number of filters is also limited in Kconfig to save memory.

Errors may occur during transmission. In case a node detects an erroneous frame, it partially overrides the current frame with an error-frame. Error-frames can either be error passive or error active, depending on the state of the controller. In case the controller is in error active state, it sends six consecutive dominant bits, which is a violation of the stuffing rule that all nodes can detect. The sender may resend the frame right after.

An initialized node can be in one of the following states:

Error-active
Error-passive
Bus-off

After initialization, the node is in the error-active state. In this state, the node is allowed to send active error frames, ACK, and overload frames. Every node has a receive- and transmit-error counter. If either the receive- or the transmit-error counter exceeds 127, the node changes to error-passive state. In this state, the node is not allowed to send error-active frames anymore. If the transmit-error counter increases further to 255, the node changes to the bus-off state. In this state, the node is not allowed to send any dominant bits to the bus. Nodes in the bus-off state may recover after receiving 128 occurrences of 11 concurrent recessive bits.

You can read more about CAN bus in this CAN Wikipedia article.

Zephyr supports following CAN features:

Standard and Extended Identifers
Filters with Masking
Loopback and Silent mode
Remote Request

Sending 

The following code snippets show how to send data.

This basic sample sends a CAN frame with standard identifier 0x123 and eight bytes of data. When passing NULL as the callback, as shown in this example, the send function blocks until the frame is sent and acknowledged by at least one other node or an error occurred. The timeout only takes effect on acquiring a mailbox. When a transmitting mailbox is assigned, sending cannot be canceled.

struct zcan_frame frame = {
        .id_type = CAN_STANDARD_IDENTIFIER,
        .rtr = CAN_DATAFRAME,
        .id = 0x123,
        .dlc = 8,
        .data = {1,2,3,4,5,6,7,8}
};
const struct device *can_dev;
int ret;

can_dev = device_get_binding("CAN_0");

ret = can_send(can_dev, &frame, K_MSEC(100), NULL, NULL);
if (ret != 0) {
        LOG_ERR("Sending failed [%d]", ret);
}

This example shows how to send a frame with extended identifier 0x1234567 and two bytes of data. The provided callback is called when the message is sent, or an error occurred. Passing K_FOREVER to the timeout causes the function to block until a transfer mailbox is assigned to the frame or an error occurred. It does not block until the message is sent like the example above.

void tx_irq_callback(int error, void *arg)
{
        char *sender = (char *)arg;

        if (error != 0) {
                LOG_ERR("Sendig failed [%d]\nSender: %s\n", error, sender);
        }
}

int send_function(const struct device *can_dev)
{
        struct zcan_frame frame = {
                .id_type = CAN_EXTENDED_IDENTIFIER,
                .rtr = CAN_DATAFRAME,
                .id = 0x1234567,
                .dlc = 2
        };

        frame.data[0] = 1;
        frame.data[1] = 2;

        return can_send(can_dev, &frame, K_FOREVER, tx_irq_callback, "Sender 1");
}

Receiving 

Frames are only received when they match a filter. The following code snippets show how to receive frames by attaching filters.

Here we have an example for a receiving callback as used for can_attach_isr(). The argument arg is passed when the filter is attached.

void rx_callback_function(struct zcan_frame *frame, void *arg)
{
        ... do something with the frame ...
}

The following snippet shows how to attach a filter with an interrupt callback. It is the most efficient but also the most critical way to receive messages. The callback function is called from an interrupt context, which means that the callback function should be as short as possible and must not block. Attaching ISRs is not allowed from userspace context.

The filter for this example is configured to match the identifier 0x123 exactly.

const struct zcan_filter my_filter = {
        .id_type = CAN_STANDARD_IDENTIFIER,
        .rtr = CAN_DATAFRAME,
        .id = 0x123,
        .rtr_mask = 1,
        .id_mask = CAN_STD_ID_MASK
};
int filter_id;
const struct device *can_dev;

can_dev = device_get_binding("CAN_0");

filter_id = can_attach_isr(can_dev, rx_callback_function, callback_arg, &my_filter);
if (filter_id < 0) {
  LOG_ERR("Unable to attach isr [%d]", filter_id);
}

Here an example for can_attach_msgq() is shown. With this function, it is possible to receive frames synchronously. This function can be called from userspace context. The size of the message queue should be as big as the expected backlog.

The filter for this example is configured to match the extended identifier 0x1234567 exactly.

const struct zcan_filter my_filter = {
        .id_type = CAN_EXTENDED_IDENTIFIER,
        .rtr = CAN_DATAFRAME,
        .id = 0x1234567,
        .rtr_mask = 1,
        .id_mask = CAN_EXT_ID_MASK
};
CAN_DEFINE_MSGQ(my_can_msgq, 2);
struct zcan_frame rx_frame;
int filter_id;
const struct device *can_dev;

can_dev = device_get_binding("CAN_0");

filter_id = can_attach_msgq(can_dev, &my_can_msgq, &my_filter);
if (filter_id < 0) {
  LOG_ERR("Unable to attach isr [%d]", filter_id);
  return;
}

while (true) {
  k_msgq_get(&my_can_msgq, &rx_frame, K_FOREVER);
  ... do something with the frame ...
}

can_detach() removes the given filter.

can_detach(can_dev, filter_id);

Setting the bitrate 

The bitrate and sampling point is initially set at runtime. To change it from the application, one can use the can_set_timing() API. This function takes three arguments. The first timing parameter sets the timing for classic CAN and arbitration phase for CAN-FD. The second parameter sets the timing of the data phase for CAN-FD. For classic CAN, you can use only the first parameter and put NULL to the second one. The can_calc_timing() function can calculate timing from a bitrate and sampling point in permille. The following example sets the bitrate to 250k baud with the sampling point at 87.5%.

struct can_timing timing;
const struct device *can_dev;
int ret;

can_dev = device_get_binding("CAN_0");

ret = can_calc_timing(can_dev, &timing, 250000, 875);
if (ret > 0) {
  LOG_INF("Sample-Point error: %d", ret);
}

if (ret < 0) {
  LOG_ERR("Failed to calc a valid timing");
  return;
}

ret = can_set_timing(can_dev, &timing, NULL);
if (ret != 0) {
  LOG_ERR("Failed to set timing");
}

SocketCAN 

Zephyr additionally supports SocketCAN, a BSD socket implementation of the Zephyr CAN API. SocketCAN brings the convenience of the well-known BSD Socket API to Controller Area Networks. It is compatible with the Linux SocketCAN implementation, where many other high-level CAN projects build on top. Note that frames are routed to the network stack instead of passed directly, which adds some computation and memory overhead.

Samples 

We have two ready-to-build samples demonstrating use of the Zephyr CAN API Zephyr CAN sample and SocketCAN sample.

API Reference 

group can_interface

CAN Interface.

Linux SocketCAN compatibility

The following structures and functions provide compatibility with the CAN frame and CAN filter formats used by Linux SocketCAN.

typedef uint32_t canid_t

CAN Identifier structure for Linux SocketCAN compatibility.

The fields in this type are:

+------+--------------------------------------------------------------+
| Bits | Description                                                  |
+======+==============================================================+
| 0-28 | CAN identifier (11/29 bit)                                   |
+------+--------------------------------------------------------------+
|  29  | Error message frame flag (0 = data frame, 1 = error message) |
+------+--------------------------------------------------------------+
|  30  | Remote transmission request flag (1 = RTR frame)             |
+------+--------------------------------------------------------------+
|  31  | Frame format flag (0 = standard 11 bit, 1 = extended 29 bit) |
+------+--------------------------------------------------------------+

static inline void can_copy_frame_to_zframe(const struct can_frame *frame, struct zcan_frame *zframe)

Translate a can_frame struct to a zcan_frame struct.

Parameters

frame – Pointer to can_frame struct.
zframe – Pointer to zcan_frame struct.

static inline void can_copy_zframe_to_frame(const struct zcan_frame *zframe, struct can_frame *frame)

Translate a zcan_frame struct to a can_frame struct.

Parameters

zframe – Pointer to zcan_frame struct.
frame – Pointer to can_frame struct.

static inline void can_copy_filter_to_zfilter(const struct can_filter *filter, struct zcan_filter *zfilter)

Translate a can_filter struct to a zcan_filter struct.

Parameters

filter – Pointer to can_filter struct.
zfilter – Pointer to zcan_filter struct.

static inline void can_copy_zfilter_to_filter(const struct zcan_filter *zfilter, struct can_filter *filter)

Translate a zcan_filter struct to a can_filter struct.

Parameters

zfilter – Pointer to zcan_filter struct.
filter – Pointer to can_filter struct.

CAN controller configuration

int can_get_core_clock(const struct device *dev, uint32_t *rate)

Get the CAN core clock rate.

Returns the CAN core clock rate. One time quantum is 1/(core clock rate).

Parameters

dev – Pointer to the device structure for the driver instance.
rate – [out] CAN core clock rate in Hz.

Returns

0 on success, or a negative error code on error

int can_calc_timing(const struct device *dev, struct can_timing *res, uint32_t bitrate, uint16_t sample_pnt)

Calculate timing parameters from bitrate and sample point.

Calculate the timing parameters from a given bitrate in bits/s and the sampling point in permill (1/1000) of the entire bit time. The bitrate must alway match perfectly. If no result can be reached for the given parameters, -EINVAL is returned.

Note

The requested sample_pnt will not always be matched perfectly. The algorithm calculates the best possible match.

Parameters

dev – Pointer to the device structure for the driver instance.
res – [out] Result is written into the can_timing struct provided.
bitrate – Target bitrate in bits/s.
sample_pnt – Sampling point in permill of the entire bit time.

Return values

0 – or positive sample point error on success.
-EINVAL – if there is no solution for the desired values.
-EIO – if can_get_core_clock() is not available.

int can_calc_timing_data(const struct device *dev, struct can_timing *res, uint32_t bitrate, uint16_t sample_pnt)

Calculate timing parameters for the data phase.

Same as can_calc_timing() but with the maximum and minimum values from the data phase.

Note

CONFIG_CAN_FD_MODE must be selected for this function to be available.

Parameters

dev – Pointer to the device structure for the driver instance.
res – [out] Result is written into the can_timing struct provided.
bitrate – Target bitrate for the data phase in bits/s
sample_pnt – Sampling point for the data phase in permille of the entire bit time.

Return values

0 – or positive sample point error on success.
-EINVAL – if there is no solution for the desired values.
-EIO – if can_get_core_clock() is not available.

int can_calc_prescaler(const struct device *dev, struct can_timing *timing, uint32_t bitrate)

Fill in the prescaler value for a given bitrate and timing.

Fill the prescaler value in the timing struct. The sjw, prop_seg, phase_seg1 and phase_seg2 must be given.

The returned bitrate error is reminder of the devision of the clock rate by the bitrate times the timing segments.

Parameters

dev – Pointer to the device structure for the driver instance.
timing – Result is written into the can_timing struct provided.
bitrate – Target bitrate.

Return values

0 – or positive bitrate error.
Negative – error code on error.

int can_set_timing(const struct device *dev, const struct can_timing *timing, const struct can_timing *timing_data)

Configure the bus timing of a CAN controller.

If the sjw equals CAN_SJW_NO_CHANGE, the sjw parameter is not changed.

Note

The parameter timing_data is only relevant for CAN-FD. If the controller does not support CAN-FD or if CONFIG_CAN_FD_MODE is not selected, the value of this parameter is ignored.

Parameters

dev – Pointer to the device structure for the driver instance.
timing – Bus timings.
timing_data – Bus timings for data phase (CAN-FD only).

Return values

0 – If successful.
-EIO – General input/output error, failed to configure device.

int can_set_mode(const struct device *dev, enum can_mode mode)

Set the CAN controller to the given operation mode.

Parameters

dev – Pointer to the device structure for the driver instance.
mode – Operation mode.

Return values

0 – If successful.
-EIO – General input/output error, failed to configure device.

static inline int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate_data)

Set the bitrate of the CAN controller.

The sample point is set to the CiA DS 301 recommended value of 87.5%.

Note

The parameter bitrate_data is only relevant for CAN-FD. If the controller does not support CAN-FD or if CONFIG_CAN_FD_MODE is not selected, the value of this parameter is ignored.

Parameters

dev – Pointer to the device structure for the driver instance.
bitrate – Desired arbitration phase bitrate.
bitrate_data – Desired data phase bitrate.

Return values

0 – If successful.
-EINVAL – bitrate cannot be met.
-EIO – General input/output error, failed to set bitrate.

CAN_SJW_NO_CHANGE: Synchronization Jump Width (SJW) value to indicate that the SJW should not be changed by the timing calculation.

Transmitting CAN frames

int can_send(const struct device *dev, const struct zcan_frame *frame, k_timeout_t timeout, can_tx_callback_t callback, void *user_data)

Transmit a CAN frame on the CAN bus.

Transmit a CAN fram on the CAN bus with optional timeout and completion callback function.

See also

can_write() for a simplified API wrapper.

Parameters

dev – Pointer to the device structure for the driver instance.
frame – CAN frame to transmit.
timeout – Timeout waiting for a empty TX mailbox or K_FOREVER.
callback – Optional callback for when the frame was sent or a transmission error occurred. If NULL, this function is blocking until frame is sent. The callback must be NULL if called from user mode.
user_data – User data to pass to callback function.

Return values

0 – if successful.
-EINVAL – if an invalid parameter was passed to the function.
-ENETDOWN – if the CAN controller is in bus-off state.
-EBUSY – if CAN bus arbitration was lost.
-EIO – if a general transmit error occurred.
-EAGAIN – on timeout.

static inline int can_write(const struct device *dev, const uint8_t *data, uint8_t length, uint32_t id, enum can_rtr rtr, k_timeout_t timeout)

Wrapper function for writing data to the CAN bus.

Simple wrapper function for can_send() without the need for filling in a zcan_frame struct. This function blocks until the data is sent or a timeout occurs.

Parameters

dev – Pointer to the device structure for the driver instance.
data – Pointer to the data to write.
length – Number of bytes to write (max. 8).
id – CAN identifier used for writing.
rtr – Write as data frame or Remote Transmission Request (RTR) frame.
timeout – Timeout waiting for an empty TX mailbox or K_FOREVER.

Return values

0 – if successful.
-EINVAL – if an invalid parameter was passed to the function.
-ENETDOWN – if the CAN controller is in bus-off state.
-EBUSY – if CAN bus arbitration was lost.
-EIO – if a general transmit error occurred.
-EAGAIN – on timeout.

Receiving CAN frames

static inline int can_attach_isr(const struct device *dev, can_rx_callback_t callback, void *user_data, const struct zcan_filter *filter)

Attach a callback function with a given CAN filter.

Attach a callback to CAN identifiers specified by a filter. Whenever a frame matching the filter is received by the CAN controller, the callback function is called in interrupt context.

If a frame matches more than one attached filter, the priority of the match is hardware dependent.

The same callback function can be attached to more than one filter.

Parameters

dev – Pointer to the device structure for the driver instance.
callback – This function is called by the CAN controller driver whenever a frame matching the filter is received.
user_data – User data to pass to callback function.
filter – Pointer to a zcan_filter structure defining the filter.

Return values

filter_id – on success.
-ENOSPC – if there are no free filters.

int can_attach_msgq(const struct device *dev, struct k_msgq *msg_q, const struct zcan_filter *filter)

Attach a message queue with a given filter.

Attach a message queue to CAN identifiers specified by a filter. Whenever a frame matching the filter is received by the CAN controller, the frame is pushed to the message queue.

If a frame matches more than one attached filter, the priority of the match is hardware dependent.

A message queue can be attached to more than one filter.

Note

The message queue must me initialized before, and the caller must have appropriate permissions on it.

Parameters

dev – Pointer to the device structure for the driver instance.
msg_q – Pointer to the already initialized k_msgq struct.
filter – Pointer to a zcan_filter structure defining the filter.

Return values

filter_id – on success.
-ENOSPC – if there are no free filters.

void can_detach(const struct device *dev, int filter_id)

Detach an ISR or CAN message queue RX filter.

This routine detaches an CAN RX filter based on the filter ID returned by can_attach_isr() or can_attach_msgq().

Parameters

dev – Pointer to the device structure for the driver instance.
filter_id – Filter ID

int can_get_max_filters(const struct device *dev, enum can_ide id_type)

Get maximum number of RX filters.

Get the maximum number of concurrent RX filters for the CAN controller.

Parameters

dev – Pointer to the device structure for the driver instance.
id_type – CAN identifier type (standard or extended).

Return values

Positive – number of maximum concurrent filters.
-EIO – General input/output error.
-ENOSYS – If this function is not implemented by the driver.

CAN_DEFINE_MSGQ(name, size)

Statically define and initialize a CAN RX message queue.

The message queue’s ring buffer contains space for size CAN frames.

Parameters

name – Name of the message queue.
size – Number of CAN frames.

CAN bus error reporting and handling

enum can_state can_get_state(const struct device *dev, struct can_bus_err_cnt *err_cnt)

Get current CAN controller state.

Returns the current state and optionally the error counter values of the CAN controller.

Parameters

dev – Pointer to the device structure for the driver instance.
err_cnt – [out] Pointer to the err_cnt destination structure or NULL.

Return values

state –

int can_recover(const struct device *dev, k_timeout_t timeout)

Recover from bus-off state.

Recover the CAN controller from bus-off state to error-active state.

Note

CONFIG_CAN_AUTO_BUS_OFF_RECOVERY must be deselected for this function to be available.

Parameters

dev – Pointer to the device structure for the driver instance.
timeout – Timeout for waiting for the recovery or K_FOREVER.

Return values

0 – on success.
-EAGAIN – on timeout.

static inline void can_register_state_change_isr(const struct device *dev, can_state_change_isr_t isr)

Register an ISR callback for the CAN controller state change interrupt.

Only one callback can be registered per controller. Calling this function again overrides any previously registered callback.

Parameters

dev – Pointer to the device structure for the driver instance.
isr – ISR callback function.

CAN utility functions

static inline uint8_t can_dlc_to_bytes(uint8_t dlc)

Convert from Data Length Code (DLC) to the number of data bytes.

Parameters

dlc – Data Length Code (DLC).

Return values

Number – of bytes.

static inline uint8_t can_bytes_to_dlc(uint8_t num_bytes)

Convert from number of bytes to Data Length Code (DLC)

Parameters

num_bytes – Number of bytes.

Return values

Data – Length Code (DLC).

CAN frame definitions

CAN_STD_ID_MASK: Bit mask for a standard (11-bit) CAN identifier.

CAN_MAX_STD_ID: Maximum value for a standard (11-bit) CAN identifier.

CAN_EXT_ID_MASK: Bit mask for an extended (29-bit) CAN identifier.

CAN_MAX_EXT_ID: Maximum value for an extended (29-bit) CAN identifier.

CAN_MAX_DLC: Maximum data length code for CAN 2.0A/2.0B.

CANFD_MAX_DLC: Maximum data length code for CAN-FD.

Typedefs

typedef void (*can_tx_callback_t)(int error, void *user_data)

Defines the application callback handler function signature.

Param error: Status of the performed send operation. See the list of return values for can_send() for value descriptions.
Param user_data: User data provided when the frame was sent.

typedef void (*can_rx_callback_t)(struct zcan_frame *frame, void *user_data)

Defines the application callback handler function signature for receiving.

Param frame: Received frame.
Param user_data: User data provided when the filter was attached.

typedef void (*can_state_change_isr_t)(enum can_state state, struct can_bus_err_cnt err_cnt)

Defines the state change Interrupt Service Routine (ISR) handler function signature.

Param state: State of the CAN controller.
Param err_cnt: CAN controller error counter values.

Enums

enum can_mode

Defines the mode of the CAN controller.

Values:

enumerator CAN_NORMAL_MODE: Normal mode.

enumerator CAN_SILENT_MODE: Controller is not allowed to send dominant bits.

enumerator CAN_LOOPBACK_MODE: Controller is in loopback mode (receives own frames).

enumerator CAN_SILENT_LOOPBACK_MODE: Combination of loopback and silent modes.

enum can_state

Defines the state of the CAN bus.

Values:

enumerator CAN_ERROR_ACTIVE: Error-active state.

enumerator CAN_ERROR_PASSIVE: Error-passive state.

enumerator CAN_BUS_OFF: Bus-off state.

enumerator CAN_BUS_UNKNOWN: Bus state unknown.

enum can_ide

Defines if the CAN frame has a standard (11-bit) or extended (29-bit) CAN identifier.

Values:

enumerator CAN_STANDARD_IDENTIFIER: Standard (11-bit) CAN identifier.

enumerator CAN_EXTENDED_IDENTIFIER: Extended (29-bit) CAN identifier.

enum can_rtr

Defines if the CAN frame is a data frame or a Remote Transmission Request (RTR) frame.

Values:

enumerator CAN_DATAFRAME: Data frame.

enumerator CAN_REMOTEREQUEST: Remote Transmission Request (RTR) frame.

struct zcan_frame

#include <can.h>

CAN frame structure.

Public Members

uint32_t id: Standard (11-bit) or extended (29-bit) CAN identifier.

uint32_t fd: Frame is in the CAN-FD frame format if set to true.

uint32_t rtr: Remote Transmission Request (RTR) flag. Use can_rtr enum for assignment.

uint32_t id_type: CAN identifier type (standard or extended). Use can_ide enum for assignment.

uint8_t dlc: Data Length Code (DLC) indicating data length in bytes.

uint8_t brs: Baud Rate Switch (BRS). Only valid for CAN-FD.

uint16_t timestamp: Captured value of the free-running timer in the CAN controller when this frame was received. The timer is incremented every bit time and captured at the start of frame bit (SOF).

Note

CONFIG_CAN_RX_TIMESTAMP must be selected for this field to be available.

union zcan_frame.[anonymous] [anonymous]: The frame payload data.

struct zcan_filter

#include <can.h>

CAN filter structure.

Public Members

uint32_t id: CAN identifier to match.

uint32_t rtr: Match data frame or Remote Transmission Request (RTR) frame.

uint32_t id_type: Standard or extended CAN identifier. Use can_ide enum for assignment.

uint32_t id_mask: CAN identifier matching mask. If a bit in this mask is 0, the value of the corresponding bit in the id field is ignored by the filter.

uint32_t rtr_mask: Data frame/Remote Transmission Request (RTR) bit matching mask. If this bit is 0, the value of the rtr field is ignored by the filter.

struct can_bus_err_cnt

#include <can.h>

CAN controller error counters.

Public Members

uint8_t tx_err_cnt: Value of the CAN controller transmit error counter.

uint8_t rx_err_cnt: Value of the CAN controller receive error counter.

struct can_timing

#include <can.h>

CAN bus timing structure.

This struct is used to pass bus timing values to the configuration and bitrate calculation functions.

The propagation segment represents the time of the signal propagation. Phase segment 1 and phase segment 2 define the sampling point. The prop_seg and phase_seg1 values affect the sampling point in the same way and some controllers only have a register for the sum of those two. The sync segment always has a length of 1 time quantum (see below).

+---------+----------+------------+------------+
|sync_seg | prop_seg | phase_seg1 | phase_seg2 |
+---------+----------+------------+------------+
                                  ^
                            Sampling-Point

1 time quantum (tq) has the length of 1/(core_clock / prescaler). The bitrate is defined by the core clock divided by the prescaler and the sum of the segments:

br = (core_clock / prescaler) / (1 + prop_seg + phase_seg1 + phase_seg2)

The Synchronization Jump Width (SJW) defines the amount of time quanta the sample point can be moved. The sample point is moved when resynchronization is needed.

Public Members

uint16_t sjw: Synchronisation jump width.

uint16_t prop_seg: Propagation segment.

uint16_t phase_seg1: Phase segment 1.

uint16_t phase_seg2: Phase segment 2.

uint16_t prescaler: Prescaler value.

struct can_frame

#include <can.h>

CAN frame for Linux SocketCAN compatibility.

Public Members

canid_t can_id: 32-bit CAN ID + EFF/RTR/ERR flags.

uint8_t can_dlc: The data length code (DLC).

uint8_t data[CAN_MAX_DLEN]: The payload data.

struct can_filter

#include <can.h>

CAN filter for Linux SocketCAN compatibility.

A filter is considered a match when received_can_id & mask == can_id & can_mask.

Public Members

canid_t can_id: The CAN identifier to match.

canid_t can_mask: The mask applied to can_id for matching.

CAN Controller

Overview

Sending

Receiving

Setting the bitrate

SocketCAN

Samples

API Reference

Overview 

Sending 

Receiving 

Setting the bitrate 

SocketCAN 

Samples 

API Reference 