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OS4 Built-In Functions
The OS4 driver includes a BIFs tab controlling 9 built-in functions. These functions, when enabled, output calculated data to the instrument system for display.

Most BIFs have alternative uses; for instance, BIF #4 can be the Wally or Vmc performance percent. The tag for each BIF can be assigned. The default tags are Users 1 thru 9.

To use a BIF, disable it, pick the alternative you wish, check the tag for output, and enable it.

The BIF code is open source, included with the OS4 package. If you want, you can write your own. Or we will do it for you.

BIF # Function Description
1a PolarSpd PC Polar speed from the PC polar. May be in addition to an instrument-based polar.
1b Time to Layline Time to the laylines from OS4 Racecourse
1c PolarSpd PC % Same as 1a except boatspeed as a percentage of polar speed.
2a TargetSpd PC Target speed from the PC polar. May be in addition to instrument targets.
2b Targ Spd + Ang Target speed and angle alternating.
2c Targ Vmc Spd Vmc target boatspeed.
2d Targ Spd PC% Same as 2a except boatspeed as a percentage of target speed.
3a Targ Angle Target angle. Switches for upwind and downwind.
3b Tar SpdU ang D PC target speed upwind, target angle downwind.
3c Vmc Targ Ang Target true wind angle for Vmc.
3d Targ Spd + Ang Same as 2a (in case you want another function on BIF 2).
4a Wally Wally boatspeed difference (i.e. +0.1 means go 0.1 knot faster than target).
4b VmcPerf % Vmc performance. Ratio of actual Vmc to ideal Vmc.
5a Vmc Crs Heading for Vmc max.
5b Crs To Steer Upwind & downwind: target course. Reaching: Vmc course.
6a Downwnd Crs The two downwind courses from OS4 Race using target angles, alternating.
6b NextLeg Crs Rhumbline of the next leg (from OS4 Race).
7 Next Leg Next leg Apparent wind angle and speed, alternating.
8a Earth True Wind direction corrected for current.
8b WallyAvg Mt Wind direction that Wally is using.
9a CrsTrk Err Distance off OS4 Race rhumbline.
9b WindSpd True Wtd Weighted windspeed true (using driver's gradient setting).

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