【DBC专题】-10-CAN DBC转换C语言代码Demo_接收Rx报文篇

CAN DBC转换C语言代码Demo_接收Rx报文篇

汽车电子助手

5324人浏览 · 2023-03-09 01:18:01

汽车电子助手 · 2023-03-09 01:18:01 发布

案例背景(共15页精讲)：
该篇博文将告诉您，CAN DBC转换C语言代码Demo，只需传递对应CAN信号关联参数，无需每个信号"左移"和"右移"，并举例介绍：在CANoe/Canalyzer中CAPL中的应用：对接收报文，进行解包。其它场景的应用，也可参考该篇。

1 背景：CAN信号在CAN 报文/Frame中位置的决定因素

2 讲解：CAN DBC转换C语言代码Demo

3 举例：在CANoe/Canalyzer中CAPL中的应用：对接收报文，进行解包

3.1 信号的字节顺序Byte Order: Intel小端模式

3.1.1 CAPL文件can的完整代码

3.1.2 系统变量定义

3.1.3 测试结果

3.2信号的字节顺序Byte Order: Motorola大端模式

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1 背景：CAN信号在CAN 报文/Frame中位置的决定因素

一个CAN信号在CAN 报文/Frame中的位置，由3个条件决定，见图1-1：

信号的起始位Startbit：默认为信号的Lsb；
信号的长度Length；
信号的字节顺序Byte Order: Intel小端模式和Motorola大端模式。

详见博文“【DBC专题】-4-DBC文件中的Signal信号字节顺序Motorola和Intel介绍https://blog.csdn.net/qfmzhu/article/details/111561710”，这里不再重复讲解。

下面我们根据这个背景，来设计一个通用算法，封装成一个函数，只需输入几个参数，即可得到对应的信号值。

图1-1

2 讲解：CAN DBC转换C语言代码Demo

2.1 定义一些宏定义

#define FRAME_TJW_ZERO_DLC  0   // unit:Byte
#define FRAME_TJW_MAX_DLC  8    // unit:Byte
#define SIGNAL_TJW_ZERO_LENGTH  0    // unit:Bit
#define SIGNAL_TJW_MAX_LENGTH  64    // unit:Bit
#define SIGNAL_TJW_INIT_VALUE  0
#define SIGNAL_TJW_INIT_MASK  0

#define SIGNAL_TJW_BYTE_ORDER_INTEL  0
#define SIGNAL_TJW_BYTE_ORDER_MOTOROLA  1

#define CAN_SIGNAL_TJW_NORMAL  0
#define CAN_SIGNAL_TJW_NO_VALUE  1
#define CAN_FRAME_TJW_DLC_OUT_OF_RANGE  2
#define INVALID_INPUT_PARAMETERS_TJW  3

/** 使用该Demo需注明出处，以表对作者的尊重 **/
/** 版权归CSDN博客“汽车电子助手”所有，https://blog.csdn.net/qfmzhu **/

2.2 定义一些结构体

typedef struct
{
   uint8 Signal_State;      // Describes the state of a signal
   uint64 Signal_Value;     // Describes the value of a signal
} Unpack_CAN_Signal;
/** 使用该Demo需注明出处，以表对作者的尊重 **/
/** 版权归CSDN博客“汽车电子助手”所有，https://blog.csdn.net/qfmzhu **/

2.3 API接口函数原型

/** 使用该Demo需注明出处，以表对作者的尊重 **/
/** 版权归CSDN博客“汽车电子助手”所有，https://blog.csdn.net/qfmzhu **/

Unpack_CAN_Signal Rx_CAN_Frame_Data_Buff_to_CAN_Signal_Hex_Fun(
uint8* data_buff,          /**Byte array of CAN data field**/
uint8 signal_start_bit,    /**Rang:0~(FRAME_TJW_MAX_DLC * 8 - 1)**/
uint8 signal_length,       /**Rang:1~SIGNAL_TJW_MAX_LENGTH**/
boolean signal_byte_order, /**0:Intel;1:Motorola**/
uint8 frame_length)        /**Rang:1~FRAME_TJW_MAX_DLC**/
{
	Unpack_CAN_Signal can_signal;
	uint8 i = 0;
	uint8 byte_num = 0;
	uint8 low_data_byte = 0;
	uint8 high_data_byte = 0;
	uint8 low_data_byte_position = 0;
	uint8 high_data_byte_position = 0;
	uint8 remaining_bit_number = 0;
	uint8 remaining_byte_number = 0;	
	uint64 can_signal_mask = SIGNAL_TJW_INIT_MASK;
	
	can_signal.Signal_State = CAN_SIGNAL_TJW_NORMAL;
	can_signal.Signal_Value = SIGNAL_TJW_INIT_VALUE;
	
	if(frame_length == FRAME_TJW_ZERO_DLC)            /**DLC of CAN frame is 0**/
	{
		can_signal.Signal_State = CAN_SIGNAL_TJW_NO_VALUE;
	}
	else if(frame_length > FRAME_TJW_MAX_DLC)         /**DLC of CAN frame is out of range**/
	{
		can_signal.Signal_State = CAN_FRAME_TJW_DLC_OUT_OF_RANGE;
	}
	else if(
	        (signal_length > (frame_length * 8))         /**Invalid signal_length: The length of the signal is not in the range of DLC**/
	        || (signal_length > SIGNAL_TJW_MAX_LENGTH)          /**Invalid signal_length: The length of the signal exceeds the maximum Unsigned of C language**/
	        || (signal_length == SIGNAL_TJW_ZERO_LENGTH)        /**Invalid signal_length: The length of the signal is not equal to 0**/				
			)
	{
		can_signal.Signal_State = INVALID_INPUT_PARAMETERS_TJW;
	}
	else
	{		
		/**Byte Order: Intel**/
		if(signal_byte_order == SIGNAL_TJW_BYTE_ORDER_INTEL)  
		{
			/**Bytes used by CAN signal,Byte[0] is low byte,Byte[frame_length] is high byte**/
			low_data_byte = signal_start_bit / 8;
			high_data_byte = (signal_start_bit + signal_length - 1) / 8;  // 2 + 6 - 1 /8 = 0;  2 + 7 - 1 /8 = 1 ;  2 + 14 - 1 /8 = 1 ;  2 + 15 - 1 /8 = 2
			
			if((high_data_byte + 1) > frame_length)  /** CAN signal is not in the range of DLC**/
			{
				can_signal.Signal_State = CAN_FRAME_TJW_DLC_OUT_OF_RANGE;
			}
			else
			{
				for(i = 0;i < signal_length;i++)  /**Generate signal mask according to signal length**/
				{
					can_signal_mask |= 0x0000000000000001 << i;
				}
					
				low_data_byte_position = signal_start_bit % 8;  /**Distance from the lowest bit of each byte**/
				
				/**CAN Signal is in a bytes**/
				if(low_data_byte == high_data_byte) 
				{					
					can_signal.Signal_Value = (((uint64)data_buff[low_data_byte]) >> low_data_byte_position) & can_signal_mask;				
				}
				/**CAN Signal in multiple bytes**/
				else
				{					
					for(byte_num = low_data_byte;byte_num <= high_data_byte;byte_num++)
					{
						if(byte_num == low_data_byte)
						{
							can_signal.Signal_Value |= ((uint64)data_buff[low_data_byte]) >> low_data_byte_position;
						}
						else
						{
							can_signal.Signal_Value |= ((uint64)data_buff[byte_num]) << ((byte_num - low_data_byte - 1) * 8 + (8 - low_data_byte_position));
						}						
					}
					
					can_signal.Signal_Value = can_signal.Signal_Value & can_signal_mask;					
				}				
			}
		}
		/**Byte Order: Motorola**/
		else  /**signal_byte_order == SIGNAL_TJW_BYTE_ORDER_MOTOROLA**/
		{
			/**Bytes used by CAN signal,Byte[0] is low byte,Byte[frame_length] is high byte**/
			high_data_byte = signal_start_bit / 8;	
			
			if((high_data_byte + 1) > frame_length)        /** CAN signal is not in the range of DLC**/
			{
		    	can_signal.Signal_State = CAN_FRAME_TJW_DLC_OUT_OF_RANGE;
			}
			else
			{
				for(i = 0;i < signal_length;i++)  /**Generate signal mask according to signal length**/
				{
					can_signal_mask |= 0x0000000000000001 << i;
				}
				
				high_data_byte_position = signal_start_bit % 8;  /**Distance from the lowest bit of each byte**/
				
				/**CAN Signal is in a bytes**/
				if(signal_length <= (8 - high_data_byte_position))
				{				
					can_signal.Signal_Value = (((uint64)data_buff[high_data_byte]) >> high_data_byte_position) & can_signal_mask;					
				}
				/**CAN Signal in multiple bytes**/
				else
				{			
					remaining_bit_number = signal_length - (8 - high_data_byte_position); // 剩余bit = 12 - (8 - 2) = 6
					
					if((remaining_bit_number % 8) != 0)     
					{
						remaining_byte_number = remaining_bit_number / 8 + 1;          // remaining_byte_number = 1
					}
					else
					{
						remaining_byte_number = remaining_bit_number / 8;
					}

					for(byte_num = high_data_byte;byte_num >= (high_data_byte - remaining_byte_number);byte_num--)  // high_data_byte = 2  remaining_byte_number = 1
					{						
						if(byte_num == high_data_byte)
						{
							can_signal.Signal_Value |= ((uint64)data_buff[high_data_byte]) >> high_data_byte_position;
						}
						else
						{
							can_signal.Signal_Value |= ((uint64)data_buff[byte_num]) << ((high_data_byte - byte_num - 1) * 8 + (8 - high_data_byte_position));
						}		
						
						if(byte_num == 0)	
						{
							break;
						}						
					}
					can_signal.Signal_Value = can_signal.Signal_Value & can_signal_mask;									
				}			
			}				
		}
	}

	return can_signal;
}
/** 使用该Demo需注明出处，以表对作者的尊重 **/
/** 版权归CSDN博客“汽车电子助手”所有，https://blog.csdn.net/qfmzhu **/

2.4 对CANFD DBC的支持

只需将宏定义FRAME_TJW_MAX_DLC的值由8调整为64，即可适配CANFD DBC。

2.5 如何使用该API接口

1、提供的demo，使用了uint8，uint64，boolean类型，在将该代码集成至开发环境中，需要注意这些类型的替换：

typedef unsigned char uint8
typedef unsigned long long uint64

2、调用函数Rx_CAN_Frame_Data_Buff_to_CAN_Signal_Hex_Fun时，需要确认传参data_buff，signal_start_bit，signal_length，signal_byte_order，frame_length的准确性，需与DBC保持一致，这样您可以得到对应信号的状态与值；