CAN is a communication protocol used in automotive and industrial control systems to allow devices to communicate with each other over a network. It is a robust protocol that is resistant to noise and interference, and it is widely used in a variety of applications.
The CAN protocol specifies how devices on the network transmit and receive messages, as well as the format of the messages themselves. CAN messages contain a message identifier, which specifies the type of message being transmitted, and data, which contains the actual message payload. The CAN protocol also specifies the data rate, which determines the speed at which messages are transmitted on the network.
To write CAN protocol code in Xilinx FreeRTOS, you will need to follow these steps:
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Set up the hardware for CAN communication. This typically involves connecting a CAN controller to the microcontroller or microprocessor that you will be used to send and receive CAN messages.
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Configure the CAN controller. This typically involves setting up the baud rate, which determines the speed at which the CAN controller communicates with other devices on the network.
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Initialize the CAN controller. This typically involves setting up the CAN controller's registers and enabling it to communicate on the network.
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Define the CAN message structure. This typically involves defining a struct that contains the fields needed to represent a CAN message, such as the message identifier, the data length, and the data itself.
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Write functions to send and receive CAN messages. These functions should use the CAN controller's registers and functions to transmit and receive messages on the network.
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Integrate the CAN code into the Xilinx FreeRTOS environment. This typically involves creating tasks or threads that use the CAN functions to send and receive messages as needed.
Here is an example of a FreeRTOS task that sends a CAN message using the MCP2515 CAN controller:
#include "FreeRTOS.h"
#include "task.h"
#include "queue.h"
#include "semphr.h"
#include "mcp2515.h"
// Define the CAN message structure
typedef struct {
uint16_t id;
uint8_t data[8];
uint8_t length;
} can_message_t;
void can_task(void *pvParameters)
{
// Initialize the MCP2515 CAN controller
mcp2515_init();
// Set up the CAN message
can_message_t message;
message.id = 0x123;
message.length = 8;
for (int i = 0; i < 8; i++) {
message.data[i] = i;
}
// Send the CAN message every 1000ms
while (1) {
mcp2515_send_message(&message);
vTaskDelay(1000 / portTICK_PERIOD_MS);
}
}
To implement CAN in a Xilinx FreeRTOS system, you will need to use a CAN driver and a CAN library.
The CAN driver is responsible for interacting with the hardware, such as a CAN controller, to send and receive CAN messages. The CAN library provides a set of APIs (Application Programming Interfaces) that can be used to send and receive CAN messages and configure the CAN driver.
Here is an example of how you might use the CAN library to send a message using the FreeRTOS CAN driver:
#include "can.h"
void send_can_message(uint32_t id, uint8_t *data, uint8_t len)
{
CanMessage msg;
msg.id = id;
msg.format = CAN_STANDARD_FORMAT;
msg.type = CAN_DATA_FRAME;
msg.data_length_code = len;
memcpy(msg.data, data, len);
CAN_Write(0, &msg, portMAX_DELAY);
}
This function sends a CAN message with the specified ID and data payload using the CAN_Write function provided by the CAN library. The CAN_Write function takes as arguments the CAN controller to use, the message to send, and a timeout value.
Here is an example of how you might use the CAN library to send and receive CAN messages in a Xilinx FreeRTOS system:
#include "can.h"
void can_task(void *pvParameters)
{
CanMessage msg;
while (1)
{
// Wait for a message to be received
if (CAN_Read(0, &msg, portMAX_DELAY) == pdTRUE)
{
// Process the received message
process_message(msg);
}
// Send a message every 500 ms
vTaskDelay(500 / portTICK_PERIOD_MS);
send_can_message(0x123, data, 8);
}
}
send_can_message is a function that sends a CAN message using the CAN library in a Xilinx FreeRTOS system. The function takes as arguments the ID of the message to send, a pointer to the data payload to include in the message, and the length of the data payload in bytes.
Here is an example of the send_can_message function:
void send_can_message(uint32_t id, uint8_t *data, uint8_t len)
{
CanMessage msg;
msg.id = id;
msg.format = CAN_STANDARD_FORMAT;
msg.type = CAN_DATA_FRAME;
msg.data_length_code = len;
memcpy(msg.data, data, len);
CAN_Write(0, &msg, portMAX_DELAY);
}
This function creates a CanMessage structure and fills in the fields with the specified ID, format, type, and data payload. It then uses the CAN_Write function provided by the CAN library to send the message. The CAN_Write function takes as arguments the CAN controller to use, the message to send, and a timeout value.
Here are some examples of functions that are commonly provided by the CAN library:
CAN_Init: Initializes the CAN driver and the specified CAN controller.CAN_Read: Reads a message from the specified CAN controller.CAN_Write: Writes a message to the specified CAN controller.CAN_SetBitrate: Configures the bitrate of the specified CAN controller.CAN_SetFilter: Configures the message filter of the specified CAN controller.CAN_GetStatus: Gets the status of the specified CAN controller.CAN_SetMode: Sets the operating mode of the specified CAN controller.CAN_SetLoopbackMode: Enables or disables loopback mode for the specified CAN controller.CAN_SetListenOnlyMode: Enables or disables listen-only mode for the specified CAN controller.CAN_SetSilentMode: Enables or disables silent mode for the specified CAN controller.CAN_SetWakeUp: Enables or disables wake-up mode for the specified CAN controller.CAN_SetBitTiming: Configures the bit timing of the specified CAN controller.
These are just a few examples of the functions that may be provided by the CAN library. The exact set of functions and their parameters will depend on the specific implementation of the CAN library.
Example of CAN send and receive in a Xilinx FreeRTOS system
#include "can.h"
#include "xparameters.h"
#include "FreeRTOS.h"
#include "task.h"
#define CAN_BASEADDR XPAR_CAN_0_BASEADDR
void can_task(void *pvParameters)
{
CanMessage msg;
CanConfig config;
config.baud_rate = 500000;
config.format = CAN_STANDARD_FORMAT;
config.id_type = CAN_EXTENDED_IDENTIFIER;
config.loopback = false;
config.silent = false;
config.timing0 = 0x04;
config.timing1 = 0x1C;
config.timing2 = 0x00;
CAN_Init(CAN_BASEADDR, &config);
while (1)
{
// Wait for a message to be received
if (CAN_Read(CAN_BASEADDR, &msg, portMAX_DELAY) == pdTRUE)
{
// Process the received message
process_message(msg);
}
// Send a message every 500 ms
vTaskDelay(500 / portTICK_PERIOD_MS);
send_can_message(CAN_BASEADDR, 0x123, data, 8);
}
}
void send_can_message(uint32_t baseaddr, uint32_t id, uint8_t *data, uint8_t len)
{
CanMessage msg;
msg.id = id;
msg.format = CAN_STANDARD_FORMAT;
msg.type = CAN_DATA_FRAME;
msg.data_length_code = len;
memcpy(msg.data, data, len);
CAN_Write(baseaddr, &msg, portMAX_DELAY);
}
This example defines a task called can_task that initializes the CAN controller using the CAN_Init function and then enters a loop to continuously read and write CAN messages. The CAN_Read function is used to read a message from the CAN controller, and the `send_
#include "can.h"
#include "xparameters.h"
#include "xcanps.h"
#include "xscugic.h"
#include "xil_exception.h"
#define CAN_DEVICE_ID XPAR_XCANPS_0_DEVICE_ID
#define INTC_DEVICE_ID XPAR_SCUGIC_SINGLE_DEVICE_ID
#define RX_INT_ID XPAR_XCANPS_0_INTR
XCanPs CanInstance;
XScuGic InterruptController;
static void SetupInterruptSystem(XScuGic *IntcInstancePtr, XCanPs *CanInstancePtr, u16 CanIntrId)
{
XScuGic_Config *IntcConfig;
Xil_ExceptionInit();
IntcConfig = XScuGic_LookupConfig(INTC_DEVICE_ID);
XScuGic_CfgInitialize(IntcInstancePtr, IntcConfig, IntcConfig->CpuBaseAddress);
XScuGic_SetPriorityTriggerType(IntcInstancePtr, CanIntrId, 0xA0, 0x3);
XScuGic_Connect(IntcInstancePtr, CanIntrId, (Xil_InterruptHandler)XCanPs_IntrHandler, (void *)CanInstancePtr);
XScuGic_Enable(IntcInstancePtr, CanIntrId);
Xil_ExceptionRegisterHandler(XIL_EXCEPTION_ID_INT, (Xil_ExceptionHandler)XScuGic_InterruptHandler, IntcInstancePtr);
Xil_ExceptionEnable();
}
int main(void)
{
XCanPs_Config *Config;
CanMessage msg;
int Status;
Config = XCanPs_LookupConfig(CAN_DEVICE_ID);
Status = XCanPs_CfgInitialize(&CanInstance, Config, Config->BaseAddr);
if (Status != XST_SUCCESS) {
return XST_FAILURE;
}
XCanPs_SelfTest(&CanInstance);
This task initializes the CAN driver and controller using the CAN_Init function and sets the bitrate to 500 kbps using the CAN_SetBitrate function. It then sets the message filter to accept all messages using the CAN_SetFilter function. The task then enters an infinite loop and waits for a message to be received using the CAN_Read function. When a message is received, it is processed by the process_message function. The task then waits for 500 ms and sends a message using the send_can_message function.
Example
#include "can.h"
#include "xparameters.h"
#define CAN_DEVICE_ID XPAR_CAN_0_DEVICE_ID
void can_task(void *pvParameters)
{
CanMessage msg;
// Initialize the CAN driver and controller
CAN_Init(CAN_DEVICE_ID);
// Set the bitrate to 500 kbps
CAN_SetBitrate(CAN_DEVICE_ID, 500000);
// Set the message filter to accept all messages
CAN_SetFilter(CAN_DEVICE_ID, 0, 0, CAN_STANDARD_FORMAT);
while (1)
{
// Wait for a message to be received
if (CAN_Read(CAN_DEVICE_ID, &msg, portMAX_DELAY) == pdTRUE)
{
// Process the received message
process_message(msg);
}
// Send a message every 500 ms
vTaskDelay(500 / portTICK_PERIOD_MS);
send_can_message(CAN_DEVICE_ID, 0x123, data, 8);
}
}
This code initializes the CAN driver using the CAN_Init function and sets up a message filter to accept all messages using the CAN_SetFilter function. It then creates a task that waits for a message to be received using the CAN_Read function and sends a message every 500 milliseconds using the send_can_message function.
Example
#include "can.h" #include "xparameters.h" #include "FreeRTOS.h" #include "task.h" #define CAN_DEVICE_ID XPAR_CAN_0_DEVICE_ID void can_task(void *pvParameters) { CanMessage msg; CanConfig config; // Initialize the CAN driver config.device_id = CAN_DEVICE_ID; config.bit_rate = 500000; config.rx_queue_size = 10; config.tx_queue_size = 10; config.rx_interrupt_priority = 5; config.tx_interrupt_priority = 5; config.loopback = 0; config.silent = 0; config.listen_only = 0; config.wake_up = 0; CAN_Init(&config); // Set the message filter to accept all messages CAN_SetFilter(0, 0, 0x7FF, CAN_STANDARD_FORMAT, CAN_DATA_FRAME); while (1) { // Wait for a message to be received if (CAN_Read(0, &msg, portMAX_DELAY) == pdTRUE) { // Process the received message process_message(msg); } // Send a message every 500 ms vTaskDelay(500 / portTICK_PERIOD_MS); send_can_message(0x123, data, 8); } } int main(void) { xTaskCreate(can_task, "CAN Task", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY + 1, NULL); vTaskStartScheduler(); return 0; } Example
#include "can.h"
#include "xparameters.h"
#include "xcanps.h"
#include "FreeRTOS.h"
#include "task.h"
#define CAN_DEVICE_ID XPAR_XCANPS_0_DEVICE_ID
#define RX_BUFFER_SIZE 16
CanMessage rx_buffer[RX_BUFFER_SIZE];
uint8_t rx_buffer_tail = 0;
void process_message(CanMessage msg)
{
// Process the received message
}
void can_task(void *pvParameters)
{
CanMessage msg;
XCanPs can;
XCanPs_Config *can_config;
int status;
// Initialize the CAN driver and controller
can_config = XCanPs_LookupConfig(CAN_DEVICE_ID);
status = XCanPs_CfgInitialize(&can, can_config, can_config->BaseAddr);
if (status != XST_SUCCESS)
{
// Error initializing the CAN driver
return;
}
XCanPs_EnterMode(&can, XCANPS_MODE_CONFIG);
XCanPs_SetBaudRatePrescaler(&can, XCANPS_BITRATE_PRESCALER_64);
XCanPs_SetBitTiming(&can, XCANPS_BTR_SJW_1, XCANPS_BTR_TS2_6, XCANPS_BTR_TS1_8);
XCanPs_ExitMode(&can, XCANPS_MODE_CONFIG);
XCanPs_EnterMode(&can, XCANPS_MODE_NORMAL);
while (1)
{
// Wait for a message to be received
if (XCanPs_Recv(&can, &msg) == XST_SUCCESS)
{
// Process the received message
process_message(msg);
}
// Send a message every 500
