Serial script and serial interface

The DriveMate serial script has been developed to access the event and accelerometer data from the FM OBC, make the relevant calculations and then control the DriveMate settings and display via commands transmitted over the serial interface. To this end, the DriveMate display is a device which is simply told how to set up, what to display and sound and feedback when a button has been pressed. This approach has been adopted as it will be easier to change a serial script in the field rather than change the firmware in the DriveMate display.

For the standard FM system events of Harsh Braking, Acceleration and Over Speeding and their corresponding warning events, the FM will be configured to the required values for the vehicle it is fitted to. For example:

• Harsh Acceleration = 6.2 mph/s
• Harsh Braking = 9.3 mph/s
• Over Speeding = 75mph

These events are calculated by the FM OBC and are read by the script when the event conditions are met. As shown in the diagram above, the 4 system events or warning events will make the script set the DriveMate display LED’s and sounder as shown in the LED sequences. In short, the system warning events drive the green and amber LED’s all on and sound a warning beep. The main events will drive all green, amber and red LED’s and sound a longer warning beep.

Cornering is calculated by the script by taking continual filtered accelerometer readings from the FM OBC as shown in the diagram above. The script uses a fixed limit i.e. maximum g-force to set the last red LED. Each LED from green to red then represents a g-force increment simply defined by:

Max g-force/7 (LED’s)

For example:

If a vehicle is being driven round corners and not generating any system events the display will indicate the g-force exerted by incrementally lighting up LED’s.

If at any time a system warning event or main event is triggered either all green and amber LED’s will be illuminated or all LED’s will be illuminated respectively. System events will always take precedence over incremental events.

Serial Interface

DriveMate will use S3 to communicate with the serial script loaded onto the FM OBC. The interface is configured to operate at 19200 baud, no parity, 1 stop bit, 8 bit data with no handshaking.

The serial message format will be as defined in the HMI/RIBAS Script Interface Specification.

FM Event & Script Relationship

All the standard system events can be configured through MiX Fleet Manager as required.

However, the cornering event does not exist as a standard event and has to be coded within the script. This means that different settings for maximum g-force will require different scripts. However, it is envisaged that a small number of scripts will cover most requirements.