CAN - Controller Area Network#
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);
}
Modules#
Enumerations#
CAN Status codes.
CAN peripheral mode.
Functions#
Initialize CAN.
Get the CAN module frequency.
Read a Message Object to find if a message was lost ; reset the 'Message Lost' flag.
Set the ROUTE registers.
Set the bitrate and its parameters.
Set the CAN operation mode.
Set the ID and the filter for a specific Message Object.
Configure valid, TX/RX, remoteTransfer for a specific Message Object.
Send data from the Message Object message.
Read data and ID from a Message Object in RAM and store it in a message.
Abort sending a message.
Reset all Message Objects and set their data to 0.
Set all CAN registers to RESETVALUE.
Write data from a message to the MIRx registers.
Send a request for writing or reading RAM of the Message Object msgNum.
Enable the Host Controller to send messages.
Give the communication capabilities state.
Waiting function.
Get the last error code and clear its register.
Indicate which message objects have received new data.
Clear one or more pending CAN status interrupts.
Disable CAN status interrupts.
Enable CAN status interrupts.
Get pending CAN status interrupt flags.
Get pending and enabled CAN status interrupt flags.
Set one or more CAN status interrupts.
Get CAN status.
Clear CAN status.
Get the error count.
Clear one or more pending CAN message interrupts.
Disable CAN message interrupts.
Enable CAN message interrupts.
Get pending CAN message interrupt flags.
Get CAN message interrupt flags that are pending and enabled.
Set one or more CAN message interrupts.
Macros#
Default initialization of CAN_Init_TypeDef.
Enumeration Documentation#
CAN_ErrorCode_TypeDef#
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. |
CAN_Mode_TypeDef#
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. |
Function Documentation#
CAN_Init#
void CAN_Init (CAN_TypeDef * can, const CAN_Init_TypeDef * init)
Initialize CAN.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
const CAN_Init_TypeDef * | [in] | init | A pointer to the CAN initialization structure. |
CAN_GetClockFrequency#
uint32_t CAN_GetClockFrequency (CAN_TypeDef * can)
Get the CAN module frequency.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
An internal prescaler of 2 is inside the CAN module.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
uint8_t | [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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
bool | [in] | active | A boolean indicating whether or not to activate the ROUTE registers. |
uint16_t | [in] | pinRxLoc | A location of the RX pin. |
uint16_t | [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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | bitrate | A wanted bitrate on the CAN bus. |
uint16_t | [in] | propagationTimeSegment | A value for the Propagation Time Segment. |
uint16_t | [in] | phaseBufferSegment1 | A value for the Phase Buffer Segment 1. |
uint16_t | [in] | phaseBufferSegment2 | A value for the Phase Buffer Segment 2. |
uint16_t | [in] | synchronisationJumpWidth | A value for the Synchronization Jump Width. |
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.
CAN_SetMode#
void CAN_SetMode (CAN_TypeDef * can, CAN_Mode_TypeDef mode)
Set the CAN operation mode.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
CAN_Mode_TypeDef | [in] | mode | Mode of operation : Init, Normal, Loopback, SilentLoopback, Silent, Basic. |
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.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
bool | [in] | useMask | A boolean to choose whether or not to use the masks. |
const CAN_MessageObject_TypeDef * | [in] | message | A Message Object. |
bool | [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. |
The initialization bit has to be 0 to use this function.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
uint8_t | [in] | msgNum | A message number of this Message Object, [1 - 32]. |
bool | [in] | valid | True if the Message Object is valid, false otherwise. |
bool | [in] | tx | True if the Message Object is used for transmission, false if used for reception. |
bool | [in] | remoteTransfer | True if the Message Object is used for remote transmission, false otherwise. |
bool | [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. |
bool | [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. |
The initialization bit has to be 0 to use this function.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
const CAN_MessageObject_TypeDef * | [in] | message | A Message Object. |
bool | [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. |
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.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
CAN_MessageObject_TypeDef * | [in] | message | A Message Object. |
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.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
uint8_t | [in] | msgNum | A message number of this Message Object, [1 - 32]. |
bool | [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. |
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().
CAN_ResetMessages#
void CAN_ResetMessages (CAN_TypeDef * can, uint8_t interface)
Reset all Message Objects and set their data to 0.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
CAN_Reset#
void CAN_Reset (CAN_TypeDef * can)
Set all CAN registers to RESETVALUE.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Leave the CAN device disabled.
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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
const CAN_MessageObject_TypeDef * | [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.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
uint8_t | [in] | msgNum | A message number of the Message Object, [1 - 32]. |
bool | [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)
Enable the Host Controller to send messages.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
bool | [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)
Give the communication capabilities state.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [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)
Waiting function.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint8_t | [in] | interface | Indicate which Message Interface Register to use. |
CAN_GetLastErrorCode#
CAN_ErrorCode_TypeDef CAN_GetLastErrorCode (CAN_TypeDef * can)
Get the last error code and clear its register.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | Pointer to CAN peripheral register block. |
Returns
return Last error code.
CAN_HasNewdata#
uint32_t CAN_HasNewdata (CAN_TypeDef * can)
Indicate which message objects have received new data.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [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)
Clear one or more pending CAN status interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | Pending CAN status interrupt source(s) to clear. |
CAN_StatusIntDisable#
void CAN_StatusIntDisable (CAN_TypeDef * can, uint32_t flags)
Disable CAN status interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN status interrupt source(s) to disable. |
CAN_StatusIntEnable#
void CAN_StatusIntEnable (CAN_TypeDef * can, uint32_t flags)
Enable CAN status interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN status interrupt source(s) to enable. |
CAN_StatusIntGet#
uint32_t CAN_StatusIntGet (CAN_TypeDef * can)
Get pending CAN status interrupt flags.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Note
This function does not clear event bits.
Returns
CAN interrupt source(s) pending.
CAN_StatusIntGetEnabled#
uint32_t CAN_StatusIntGetEnabled (CAN_TypeDef * can)
Get pending and enabled CAN status interrupt flags.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Note
This function does not clear event bits.
Returns
CAN interrupt source(s) pending and enabled.
CAN_StatusIntSet#
void CAN_StatusIntSet (CAN_TypeDef * can, uint32_t flags)
Set one or more CAN status interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN status interrupt source(s) to set to pending. |
CAN_StatusGet#
uint32_t CAN_StatusGet (CAN_TypeDef * can)
Get CAN status.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [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)
Clear CAN status.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN status bits to clear. |
CAN_GetErrorCount#
uint32_t CAN_GetErrorCount (CAN_TypeDef * can)
Get the error count.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Returns
Error count.
CAN_MessageIntClear#
void CAN_MessageIntClear (CAN_TypeDef * can, uint32_t flags)
Clear one or more pending CAN message interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | Pending CAN message interrupt source(s) to clear. |
CAN_MessageIntDisable#
void CAN_MessageIntDisable (CAN_TypeDef * can, uint32_t flags)
Disable CAN message interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN message interrupt source(s) to disable. |
CAN_MessageIntEnable#
void CAN_MessageIntEnable (CAN_TypeDef * can, uint32_t flags)
Enable CAN message interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN message interrupt source(s) to enable. |
CAN_MessageIntGet#
uint32_t CAN_MessageIntGet (CAN_TypeDef * can)
Get pending CAN message interrupt flags.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Note
This function does not clear event bits.
Returns
CAN message interrupt source(s) pending.
CAN_MessageIntGetEnabled#
uint32_t CAN_MessageIntGetEnabled (CAN_TypeDef * can)
Get CAN message interrupt flags that are pending and enabled.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
Note
This function does not clear event bits.
Returns
CAN message interrupt source(s) pending and enabled.
CAN_MessageIntSet#
void CAN_MessageIntSet (CAN_TypeDef * can, uint32_t flags)
Set one or more CAN message interrupts.
Type | Direction | Argument Name | Description |
---|---|---|---|
CAN_TypeDef * | [in] | can | A pointer to the CAN peripheral register block. |
uint32_t | [in] | flags | CAN message interrupt source(s) to set as pending. |