Top Level V+ Design

feature author: Paul Halliday

The best place to start is with the top-level functionality. This typically involves dealing with the host computer’s frame counter and the instructor’s volume controls. Figure 3 contains the TopLevel worksheet file for the Beech 1900D. Shown here are six input ports that are found in the VPlusPorts table described in the Host Computer To SimPhonics Computer Interface section. The six input ports are described as follows.

1. Host Counter – Host computer’s frame counter. Should be incremented at a rate of at least 30 Hz.

2. Mute Warnings & Tones – Used to mute GPWS, TCAS, warning horns, and nav tones.

3. Mute Environmental Sound – Mutes all environment sounds (i.e., engines, air impact, weather, flaps, landing gear, tires, runway rumble, windshield wipers, cockpit ventilation, and explosive decompression).

4. Instructor’s Sound Level Control – Variable volume range for setting the volume of the environmental sounds.

5. Ground Speed – Speed of the aircraft along the ground.

6. Air Impact Pressure – Speed of the air against the aircraft.

The Host Counter input port is connected directly to a Watch Dog Timer with a timeout value set to 10. If the Host Counter fails to update within 10 V+ frames, the Watch Dog Timer will go high, causing the Master Volume and Warnings & Tones Volume to go to zero.

At the top left of the worksheet is a constant tied directly to the Global Switch Control object. This acts as the Manual/Host Control Switch. The rest of the worksheets monitor this switch for debugging purposes. When the Global Switch Control is on, the switch monitors may set their own values to be used for testing or debugging. See the help page on the Global Switch Control for more information.

On the Beech 1900D, we divided all of the sounds into two groups: Environmental and Warning & Tones. Environmental sounds come from the engines, control surfaces, wind, etc. Warnings & Tones are the sounds that are specifically generated to capture the pilots’ attention. Master volume control is separate for both of these groups. The output of the Watch Dog Timer, and input items 2, 3, and 4 identified above are used to set the worksheet connectors Master Volume and Warnings & Tones Volume shown at the right of the TopLevel worksheet. The output of the Watch Dog Timer is fed into a Logical And object, which is then fed into a Logical Or object, which is then inverted and fed into a First Order Low Pass Filter, which is fed into a Float Linear Function Interpolator (LFI), and finally finds its way to the worksheet connectors. The outcome of all this is to provide a master volume value to be used by all the WAVE file players in the system. You’ll see how this works in subsequent worksheet designs.

Let’s take a closer look at the Soft Mute Integrators shown on the worksheet. They use a low pass filter and an LFI to affect the decay and attack characteristics of the sounds that are playing when a mute/unmute is issued by the host. The effect is such that a gradual shut-off and a gradual ramp-up of the sounds. This is especially nice after coming out of a simulation freeze – it keeps from abruptly startling people in the simulator.

The Ground Speed and Air Impact Pressure input ports are wired directly into worksheet connectors. We placed them in the TopLevel worksheet since there are several other worksheets that use them as input.

Figure3.  TopLevel Design

Our simulation had V+ running 25 millisecond frames. Ten of these frames would be 250 milliseconds, or ¼ of a second.