The SPEEDBOX20 outputs serial data in Race Technology format. This is, essentially, a simple wrapper comprising a channel number and a checksum, around raw hex (big-endian) integer data values. A detailed description of the serial data format is given in Section 10 of this manual and is also available from the Race Technology online help system. The serial data format is also fully documented in the knowledge base on our website (under Software->Main Analysis Software->Technical->Serial Data Format). Source code in VB6 and ANSI C is also available for converting the serial data into physical values.
The acceleration and combined speed message is output at 200Hz, and the GPS data is output at 20Hz. The acceleration and combined speed message is 11bytes long. This takes approximately 1ms to transmit at 115200kbps. There is a maximum latency between the acceleration reading and the start of transmission within the SPEEDBOX20 of 0.1ms This means that the combined speed and acceleration serial output should attain a latency of less than 2ms. The serial messages outputting the GPS data will have a latency of 50 – 100ms from the point to which the data refers. One of the messages, however, contains the GPS time, which can be used to refer the data from each burst of 20Hz messages to a given point in time. The serial messages can be viewed and logged on the PC, using the monitor program provided with the Race Technology software suite (see the section of this manual referring to the PC software).