A British IT SJA1000 CAN communication interface functions extended application description

On the basis of the interface function provided by the existing CAN_API.H, the CAN interface communication is introduced, which is mainly for each received data plus a time label to support real-time control applications. For compatibility with previous interface functions, can_api.h remain unchanged, another British record company defines a can_api_ex.h, defines the CAN data packet structure with time tags in the file. Typedef struct { // CAN data message ID, where bit 0-28: CAN identifier (11/29 bit) bit 29: error frame flag (0 = data frame, 1 = error frame) bit 30: remote transmission request flag (1 = rtr frame) bit 31: frame format flag (0 = standard 11 bit, 1 = extended 29 bit) DWORD dwCAN_ID; // CAN data length of the data packets DWORD dwCAN_DatLen; Data // CAN data packets UCHAR ucDat [8]; // CAN data packet time stamp in milliseconds DWORD dwTimeTick; } CAN_FRAME, * PCAN_FRAME; CAN acquiring time-stamped received message, may be implemented by a standard calling the ReadFile (), the respective transmission function can call the WriteFile () to process. The following method to receive the thread acquiring CAN data packets with a time stamp: WaitForSingleObject (ceCAN->m_hRxEvent, 15); { dwLen = 0; bResult = ReadFile (ceCAN->m_hCAN, & CeCAN->can_frame, sizeof (CAN_FRAME), & dwLen, NULL); if (dwLen == sizeof (CAN_FRAME)) // receive a can frame { if (dwLastTimeTick == 0) { printf ( '0x% 08x -% ld \ n', ceCAN->can_frame.dwCAN_ID, ceCAN->can_frame.dwTimeTick); dwLastTimeTick = ceCAN->can_frame.dwTimeTick; } Else { printf ( '0x% 08x -% ld \ n', ceCAN->can_frame.dwCAN_ID, ceCAN->can_frame.dwTimeTick-dwLastTimeTick); dwLastTimeTick = ceCAN->can_frame.dwTimeTick; } } } After testing, the embedded time stamp record CAN board in the UK to ensure accuracy in ± 1ms. Since the CAN data read time-stamped message uses the standard system function ReadFile, so interested in the extension and old customers, the need for the existing British record embedded motherboards WinCE kernel upgrade, can_api.lib do not need any changes. Referring particularly can_api.h interface function defined in "SJA1000 based CAN communication interface function for use" article. Interested customers can create and British technical support. Read more

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