The SPEEDBOX20 outputs nine CAN messages using addresses 500h to 508h. In addition to this, the RTK option provides a further 3 messages, on addresses 509h to 50Bh. Message 500h contains the longitudinal and lateral acceleration values, as well as the combined speed output. It is output continuously at 200Hz. Message 501h is the status message containing, amongst other information, the GPS status and the number of satellites locked. It is output at 1Hz until a GPS solution is obtained and at 20Hz thereafter. The remaining CAN messages are only output once a GPS solution has been obtained. They are then output at 20Hz. A detailed description of the content of each message is given in Section 10 of this manual and is also available from the Race Technology online help system or the Race Technology website Knowledge Base. A CANdb file is also available if required.
In the case of the CAN output, the latency depends on both the presence of other traffic on the CAN network and on the bit rate that has been selected. This means that it cannot be considered deterministic. CAN message 500h - containing the accelerations and the combined speed - has the lowest latency. The remaining CAN messages, outputting the GPS data, typically have a latency of between 50 to 100ms after the point to which the data refers. The messages may be aligned with the GPS time to which they pertain with reference to the GPS time field in CAN message 502h.
The CAN addressing mode may be set to either 11 or 29bit and the SPEEDBOX20 can output CAN bitrates of 125kbps, 250kbps, 500kbps and 1mbps, set using the configuration software.
Note: You must properly terminate your CAN equipment to avoid any communication failure and to ensure the correct behaviour of the CAN interface. Read How do I properly terminate my RT CAN equipment section for more details on this.