CAN - Controller Area Network

Description

Controller Area Network API.

The Controller Area Network Interface Bus (CAN) implements a multi-master serial bus for connecting microcontrollers and devices, also known as nodes, to communicate with each other in applications without a host computer. CAN is a message-based protocol, designed originally for automotive applications, but also used in many other scenarios. The complexity of a node can range from a simple I/O device up to an embedded computer with a CAN interface and sophisticated software. The node may also be a gateway allowing a standard computer to communicate over a USB or Ethernet port to the devices on a CAN network. Devices are connected to the bus through a host processor, a CAN controller, and a CAN transceiver.

#include "em_can.h"
#include "em_cmu.h"
#include "em_gpio.h"
void CAN_sendExample( void )
{
CMU_ClockEnable ( cmuClock_HFPER , true );
CMU_ClockEnable ( cmuClock_CAN0 , true );
CMU_ClockEnable ( cmuClock_GPIO , true );
CAN_Reset (CAN_DEVICE);
CAN_Mode_TypeDef mode = canModeInit;
CAN_SetMode (CAN_DEVICE, mode);
GPIO_PinModeSet ($gpioPortX, $X_bit, gpioModeInput , 0);
GPIO_PinModeSet ($gpioPortY, $Y_bit, gpioModePushPull , 0);
CAN_SetRoute (CAN_DEVICE, true , $x, $y);
CAN_SetBitTiming (CAN_DEVICE, 100000, 1, 4, 4, 1);
mode = canModeNormal ;
CAN_SetMode (CAN_DEVICE, mode);
CAN_MessageObject_TypeDef message;
message. msgNum = 1;
message. extended = false ;
message. id = 19;
message. dlc = 8;
uint32_t i;
for (i = 0; i < message. dlc ; ++i) {
message. data [i] = i;
}
CAN_ConfigureMessageObject (CAN_DEVICE, 0, message. msgNum , true , true , false , true );
CAN_SendMessage (CAN_DEVICE, 0, &message, true );
}

Data Structures

struct CAN_MessageObject_TypeDef
CAN Message Object TypeDef structure.
struct CAN_Init_TypeDef
CAN initialization structure.

Functions

void CAN_Init (CAN_TypeDef *can, const CAN_Init_TypeDef *init)
Initialize CAN.
uint32_t CAN_GetClockFrequency (CAN_TypeDef *can)
Get the CAN module frequency.
bool CAN_MessageLost (CAN_TypeDef *can, uint8_t interface, uint8_t msgNum)
Read a Message Object to find if a message was lost ; reset the 'Message Lost' flag.
void CAN_SetRoute (CAN_TypeDef *can, bool active, uint16_t pinRxLoc, uint16_t pinTxLoc)
Set the ROUTE registers.
void CAN_SetBitTiming (CAN_TypeDef *can, uint32_t bitrate, uint16_t propagationTimeSegment, uint16_t phaseBufferSegment1, uint16_t phaseBufferSegment2, uint16_t synchronisationJumpWidth)
Set the bitrate and its parameters.
void CAN_SetMode (CAN_TypeDef *can, CAN_Mode_TypeDef mode)
Set the CAN operation mode.
void CAN_SetIdAndFilter (CAN_TypeDef *can, uint8_t interface, bool useMask, const CAN_MessageObject_TypeDef *message, bool wait)
Set the ID and the filter for a specific Message Object.
void CAN_ConfigureMessageObject (CAN_TypeDef *can, uint8_t interface, uint8_t msgNum, bool valid, bool tx, bool remoteTransfer, bool endOfBuffer, bool wait)
Configure valid, TX/RX, remoteTransfer for a specific Message Object.
void CAN_SendMessage (CAN_TypeDef *can, uint8_t interface, const CAN_MessageObject_TypeDef *message, bool wait)
Send data from the Message Object message.
bool CAN_ReadMessage (CAN_TypeDef *can, uint8_t interface, CAN_MessageObject_TypeDef *message)
Read data and ID from a Message Object in RAM and store it in a message.
void CAN_AbortSendMessage (CAN_TypeDef *can, uint8_t interface, uint8_t msgNum, bool wait)
Abort sending a message.
void CAN_ResetMessages (CAN_TypeDef *can, uint8_t interface)
Reset all Message Objects and set their data to 0.
void CAN_Reset (CAN_TypeDef *can)
Set all CAN registers to RESETVALUE.
void CAN_WriteData (CAN_TypeDef *can, uint8_t interface, const CAN_MessageObject_TypeDef *message)
Write data from a message to the MIRx registers.
void CAN_SendRequest (CAN_TypeDef *can, uint8_t interface, uint8_t msgNum, bool wait)
Send a request for writing or reading RAM of the Message Object msgNum.
void CAN_Enable (CAN_TypeDef *can, bool enable)
Enable the Host Controller to send messages.
bool CAN_IsEnabled (CAN_TypeDef *can)
Give the communication capabilities state.
void CAN_ReadyWait (CAN_TypeDef *can, uint8_t interface)
Waiting function.
CAN_ErrorCode_TypeDef CAN_GetLastErrorCode (CAN_TypeDef *can)
Get the last error code and clear its register.
uint32_t CAN_HasNewdata (CAN_TypeDef *can)
Indicate which message objects have received new data.
void CAN_StatusIntClear (CAN_TypeDef *can, uint32_t flags)
Clear one or more pending CAN status interrupts.
void CAN_StatusIntDisable (CAN_TypeDef *can, uint32_t flags)
Disable CAN status interrupts.
void CAN_StatusIntEnable (CAN_TypeDef *can, uint32_t flags)
Enable CAN status interrupts.
uint32_t CAN_StatusIntGet (CAN_TypeDef *can)
Get pending CAN status interrupt flags.
uint32_t CAN_StatusIntGetEnabled (CAN_TypeDef *can)
Get pending and enabled CAN status interrupt flags.
void CAN_StatusIntSet (CAN_TypeDef *can, uint32_t flags)
Set one or more CAN status interrupts.
uint32_t CAN_StatusGet (CAN_TypeDef *can)
Get CAN status.
void CAN_StatusClear (CAN_TypeDef *can, uint32_t flags)
Clear CAN status.
uint32_t CAN_GetErrorCount (CAN_TypeDef *can)
Get the error count.
void CAN_MessageIntClear (CAN_TypeDef *can, uint32_t flags)
Clear one or more pending CAN message interrupts.
void CAN_MessageIntDisable (CAN_TypeDef *can, uint32_t flags)
Disable CAN message interrupts.
void CAN_MessageIntEnable (CAN_TypeDef *can, uint32_t flags)
Enable CAN message interrupts.
uint32_t CAN_MessageIntGet (CAN_TypeDef *can)
Get pending CAN message interrupt flags.
uint32_t CAN_MessageIntGetEnabled (CAN_TypeDef *can)
Get CAN message interrupt flags that are pending and enabled.
void CAN_MessageIntSet (CAN_TypeDef *can, uint32_t flags)
Set one or more CAN message interrupts.

Macros

#define CAN_INIT_DEFAULT
Default initialization of CAN_Init_TypeDef .

Enumerations

enum CAN_ErrorCode_TypeDef {
canErrorNoError = CAN_STATUS_LEC_NONE,
canErrorStuff = CAN_STATUS_LEC_STUFF,
canErrorForm = CAN_STATUS_LEC_FORM,
canErrorAck = CAN_STATUS_LEC_ACK,
canErrorBit1 = CAN_STATUS_LEC_BIT1,
canErrorBit0 = CAN_STATUS_LEC_BIT0,
canErrorCrc = CAN_STATUS_LEC_CRC,
canErrorUnused = CAN_STATUS_LEC_UNUSED
}
CAN Status codes.
enum CAN_Mode_TypeDef {
canModeNormal ,
canModeBasic ,
canModeLoopBack ,
canModeSilentLoopBack ,
canModeSilent
}
CAN peripheral mode.

Function Documentation

◆ CAN_Init()

void CAN_Init ( CAN_TypeDef * can,
const CAN_Init_TypeDef * init
)

Initialize CAN.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] init A pointer to the CAN initialization structure.

◆ CAN_GetClockFrequency()

uint32_t CAN_GetClockFrequency ( CAN_TypeDef * can )

Get the CAN module frequency.

An internal prescaler of 2 is inside the CAN module.

Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
A clock value.

◆ CAN_MessageLost()

bool CAN_MessageLost ( CAN_TypeDef * can,
uint8_t interface,
uint8_t msgNum
)

Read a Message Object to find if a message was lost ; reset the 'Message Lost' flag.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] msgNum A message number of the Message Object, [1 - 32].
Returns
True if a message was lost, false otherwise.

◆ CAN_SetRoute()

void CAN_SetRoute ( CAN_TypeDef * can,
bool active,
uint16_t pinRxLoc,
uint16_t pinTxLoc
)

Set the ROUTE registers.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] active A boolean indicating whether or not to activate the ROUTE registers.
[in] pinRxLoc A location of the RX pin.
[in] pinTxLoc A location of the TX pin.

◆ CAN_SetBitTiming()

void CAN_SetBitTiming ( CAN_TypeDef * can,
uint32_t bitrate,
uint16_t propagationTimeSegment,
uint16_t phaseBufferSegment1,
uint16_t phaseBufferSegment2,
uint16_t synchronisationJumpWidth
)

Set the bitrate and its parameters.

Multiple parameters need to be properly configured. See the reference manual for a detailed description. Careful : the BRP (Baud Rate Prescaler) is calculated by: 'brp = freq / (period * bitrate);'. freq is the frequency of the CAN device, period the time of transmission of a bit. The result is an uint32_t. Hence it's truncated, causing an approximation error. This error is non negligible when the period is high, the bitrate is high, and frequency is low.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] bitrate A wanted bitrate on the CAN bus.
[in] propagationTimeSegment A value for the Propagation Time Segment.
[in] phaseBufferSegment1 A value for the Phase Buffer Segment 1.
[in] phaseBufferSegment2 A value for the Phase Buffer Segment 2.
[in] synchronisationJumpWidth A value for the Synchronization Jump Width.

◆ CAN_SetMode()

void CAN_SetMode ( CAN_TypeDef * can,
CAN_Mode_TypeDef mode
)

Set the CAN operation mode.

In initialization mode, the CAN module is deactivated. Reset the messages in all other modes to be sure that there is no leftover data that needs to be configured before use.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] mode Mode of operation : Init, Normal, Loopback, SilentLoopback, Silent, Basic.

◆ CAN_SetIdAndFilter()

void CAN_SetIdAndFilter ( CAN_TypeDef * can,
uint8_t interface,
bool useMask,
const CAN_MessageObject_TypeDef * message,
bool wait
)

Set the ID and the filter for a specific Message Object.

The initialization bit has to be 0 to use this function.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] useMask A boolean to choose whether or not to use the masks.
[in] message A Message Object.
[in] wait If true, wait for the end of the transfer between the MIRx registers and the RAM to exit. If false, exit immediately, the transfer can still be in progress.

◆ CAN_ConfigureMessageObject()

void CAN_ConfigureMessageObject ( CAN_TypeDef * can,
uint8_t interface,
uint8_t msgNum,
bool valid,
bool tx,
bool remoteTransfer,
bool endOfBuffer,
bool wait
)

Configure valid, TX/RX, remoteTransfer for a specific Message Object.

The initialization bit has to be 0 to use this function.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] msgNum A message number of this Message Object, [1 - 32].
[in] valid True if the Message Object is valid, false otherwise.
[in] tx True if the Message Object is used for transmission, false if used for reception.
[in] remoteTransfer True if the Message Object is used for remote transmission, false otherwise.
[in] endOfBuffer True if it is for a single Message Object or the end of a FIFO buffer, false if the Message Object is part of a FIFO buffer and not the last.
[in] wait If true, wait for the end of the transfer between the MIRx registers and the RAM to exit. If false, exit immediately, the transfer can still be in progress.

◆ CAN_SendMessage()

void CAN_SendMessage ( CAN_TypeDef * can,
uint8_t interface,
const CAN_MessageObject_TypeDef * message,
bool wait
)

Send data from the Message Object message.

If the message is configured as TX and remoteTransfer = 0, calling this function will send the data of this Message Object if its parameters are correct. If the message is TX and remoteTransfer = 1, this function will set the data of message to RAM and exit. Data will be automatically sent after reception of a remote frame. If the message is RX and remoteTransfer = 1, this function will send a remote frame to the corresponding ID. If the message is RX and remoteTransfer = 0, the user shouldn't call this function. It will also send a remote frame.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] message A Message Object.
[in] wait If true, wait for the end of the transfer between the MIRx registers and RAM to exit. If false, exit immediately. The transfer can still be in progress.

◆ CAN_ReadMessage()

bool CAN_ReadMessage ( CAN_TypeDef * can,
uint8_t interface,
CAN_MessageObject_TypeDef * message
)

Read data and ID from a Message Object in RAM and store it in a message.

Read the information from RAM on this Message Object. Data and the configuration of the Message Object is read. The information is only read if the message stored in the Message Object is new and valid.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] message A Message Object.
Returns
True if the Message Object in RAM holds a new and valid message, which was not read earlier, false otherwise.

◆ CAN_AbortSendMessage()

void CAN_AbortSendMessage ( CAN_TypeDef * can,
uint8_t interface,
uint8_t msgNum,
bool wait
)

Abort sending a message.

Set the TXRQST of the CTRL register to 0. Doesn't touch data or the other parameters. The user can call CAN_SendMessage() to send the object after using CAN_AbortSendMessage() .

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] msgNum A message number of this Message Object, [1 - 32].
[in] wait If true, wait for the end of the transfer between the MIRx registers and the RAM to exit. If false, exit immediately. The transfer can still be in progress.

◆ CAN_ResetMessages()

void CAN_ResetMessages ( CAN_TypeDef * can,
uint8_t interface
)

Reset all Message Objects and set their data to 0.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.

◆ CAN_Reset()

void CAN_Reset ( CAN_TypeDef * can )

Set all CAN registers to RESETVALUE.

Leave the CAN device disabled.

Parameters
[in] can A pointer to the CAN peripheral register block.

◆ CAN_WriteData()

void CAN_WriteData ( CAN_TypeDef * can,
uint8_t interface,
const CAN_MessageObject_TypeDef * message
)

Write data from a message to the MIRx registers.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] message A Message Object.

◆ CAN_SendRequest()

void CAN_SendRequest ( CAN_TypeDef * can,
uint8_t interface,
uint8_t msgNum,
bool wait
)

Send a request for writing or reading RAM of the Message Object msgNum.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.
[in] msgNum A message number of the Message Object, [1 - 32].
[in] wait If true, wait for the end of the transfer between the MIRx registers and the RAM to exit. If false, exit immediately. The transfer can still be in progress.

◆ CAN_Enable()

void CAN_Enable ( CAN_TypeDef * can,
bool enable
)
inline

Enable the Host Controller to send messages.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] enable True to enable CAN device, false to disable it. If the CAN device is enabled, it goes to normal mode (the default working mode).

◆ CAN_IsEnabled()

bool CAN_IsEnabled ( CAN_TypeDef * can )
inline

Give the communication capabilities state.

Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
True if the Host Controller can send messages, false otherwise.

◆ CAN_ReadyWait()

void CAN_ReadyWait ( CAN_TypeDef * can,
uint8_t interface
)
inline

Waiting function.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] interface Indicate which Message Interface Register to use.

◆ CAN_GetLastErrorCode()

CAN_ErrorCode_TypeDef CAN_GetLastErrorCode ( CAN_TypeDef * can )
inline

Get the last error code and clear its register.

Parameters
[in] can Pointer to CAN peripheral register block.
Returns
return Last error code.

◆ CAN_HasNewdata()

uint32_t CAN_HasNewdata ( CAN_TypeDef * can )
inline

Indicate which message objects have received new data.

Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
State of MESSAGEDATA register indicating which message objects have received new data.

◆ CAN_StatusIntClear()

void CAN_StatusIntClear ( CAN_TypeDef * can,
uint32_t flags
)
inline

Clear one or more pending CAN status interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags Pending CAN status interrupt source(s) to clear.

◆ CAN_StatusIntDisable()

void CAN_StatusIntDisable ( CAN_TypeDef * can,
uint32_t flags
)
inline

Disable CAN status interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN status interrupt source(s) to disable.

◆ CAN_StatusIntEnable()

void CAN_StatusIntEnable ( CAN_TypeDef * can,
uint32_t flags
)
inline

Enable CAN status interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN status interrupt source(s) to enable.

◆ CAN_StatusIntGet()

uint32_t CAN_StatusIntGet ( CAN_TypeDef * can )
inline

Get pending CAN status interrupt flags.

Note
This function does not clear event bits.
Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
CAN interrupt source(s) pending.

◆ CAN_StatusIntGetEnabled()

uint32_t CAN_StatusIntGetEnabled ( CAN_TypeDef * can )
inline

Get pending and enabled CAN status interrupt flags.

Note
This function does not clear event bits.
Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
CAN interrupt source(s) pending and enabled.

◆ CAN_StatusIntSet()

void CAN_StatusIntSet ( CAN_TypeDef * can,
uint32_t flags
)
inline

Set one or more CAN status interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN status interrupt source(s) to set to pending.

◆ CAN_StatusGet()

uint32_t CAN_StatusGet ( CAN_TypeDef * can )
inline

Get CAN status.

Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
A value of CAN register STATUS.

◆ CAN_StatusClear()

void CAN_StatusClear ( CAN_TypeDef * can,
uint32_t flags
)
inline

Clear CAN status.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN status bits to clear.

◆ CAN_GetErrorCount()

uint32_t CAN_GetErrorCount ( CAN_TypeDef * can )
inline

Get the error count.

Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
Error count.

◆ CAN_MessageIntClear()

void CAN_MessageIntClear ( CAN_TypeDef * can,
uint32_t flags
)
inline

Clear one or more pending CAN message interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags Pending CAN message interrupt source(s) to clear.

◆ CAN_MessageIntDisable()

void CAN_MessageIntDisable ( CAN_TypeDef * can,
uint32_t flags
)
inline

Disable CAN message interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN message interrupt source(s) to disable.

◆ CAN_MessageIntEnable()

void CAN_MessageIntEnable ( CAN_TypeDef * can,
uint32_t flags
)
inline

Enable CAN message interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN message interrupt source(s) to enable.

◆ CAN_MessageIntGet()

uint32_t CAN_MessageIntGet ( CAN_TypeDef * can )
inline

Get pending CAN message interrupt flags.

Note
This function does not clear event bits.
Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
CAN message interrupt source(s) pending.

◆ CAN_MessageIntGetEnabled()

uint32_t CAN_MessageIntGetEnabled ( CAN_TypeDef * can )
inline

Get CAN message interrupt flags that are pending and enabled.

Note
This function does not clear event bits.
Parameters
[in] can A pointer to the CAN peripheral register block.
Returns
CAN message interrupt source(s) pending and enabled.

◆ CAN_MessageIntSet()

void CAN_MessageIntSet ( CAN_TypeDef * can,
uint32_t flags
)
inline

Set one or more CAN message interrupts.

Parameters
[in] can A pointer to the CAN peripheral register block.
[in] flags CAN message interrupt source(s) to set as pending.

Macro Definition Documentation

◆ CAN_INIT_DEFAULT

#define CAN_INIT_DEFAULT
Value:
{ \
true, \
true, \
100000, \
1, \
4, \
4, \
1 \
}

Default initialization of CAN_Init_TypeDef .

The total duration of a bit with these default parameters is 10 tq (time quantum : tq = brp/fsys, brp being the baudrate prescaler and being set according to the wanted bitrate, fsys beeing the CAN device frequency).

Enumeration Type Documentation

◆ CAN_ErrorCode_TypeDef

enum CAN_ErrorCode_TypeDef

CAN Status codes.

Enumerator
canErrorNoError

No error occurred during the last CAN bus event.

canErrorStuff

More than 5 equal bits in a sequence have occurred in a part of a received message where this is not allowed.

canErrorForm

A fixed format part of a received frame has the wrong format.

canErrorAck

The message this CAN Core transmitted was not acknowledged by another node.

canErrorBit1

A wrong monitored bus value : dominant when the module wants to send a recessive.

canErrorBit0

A wrong monitored bus value : recessive when the module intends to send a dominant.

canErrorCrc

CRC check sum incorrect.

canErrorUnused

Unused.

No new error since the CPU wrote this value.

◆ CAN_Mode_TypeDef

enum CAN_Mode_TypeDef

CAN peripheral mode.

Enumerator
canModeNormal

CAN peripheral in Normal mode : ready to send and receive messages.

canModeBasic

CAN peripheral in Basic mode : no use of the RAM.

canModeLoopBack

CAN peripheral in Loopback mode : input from the CAN bus is disregarded and comes from TX instead.

canModeSilentLoopBack

CAN peripheral in SilentLoopback mode : input from the CAN bus is disregarded and comes from TX instead ; no output on the CAN bus.

canModeSilent

CAN peripheral in Silent mode : no output on the CAN bus.

If required to send a dominant bit, it's rerouted internally so that the CAN module monitors it but the CAN bus stays recessive.