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Appendix A. Configuring the CL system for "Potentiometer-less" operation.

In its standard configuration the CL system uses game-controller joystick card potentiometers to report control axis position (see the standard system wiring diagram). This potentiometer data is required for the power-up calibration of the BLDRV-12/24 driver cards, and also as control position input to the flight simulator software.

For systems using BLDRV-12/24 driver cards with firmware dsPIC v35 and 20X v28 (or later) the system can be operated WITHOUT potentiometer position data on the main control axes. This allows the control mechanisms to be built without position reporting potentiometers - a significant simplification of the build. Instead control axis position is derived from the motor encoder position and is sent directly to FS by the BFF CL Software v1.1 (or later) via the FSUIPC control input offsets.

The "potentiometer-less" system wiring configuration is shown here.

Although this produces a simpler system, it does mean that control input to FS is only available when the CL system cards are powered-up and calibrated and the BFF CL Software is running. When the CL system is inactive there will be no control input to FS from the FFB flight controls. A separate simple joystick configured as a standard game-controller input to FS might prove useful for controlling FS in circumstances when the CL system is inactive. So long as the output from this joystick is clean (no jitter) FS will ignore it whilst it is not in use.

To configure the CL system for pot-less operation the driver cards must be pre-set, and then a configuration change made to the CL software background process settings.

"Potentiometer-less" operation configuration steps

• Pre-set the driver cards for "potentiometer-less" calibration. This is a once-only procedure carried out using the BFF Driver Test App v28+. Once set, the cards will be able to complete their power-up calibration without the presence of live game-controller joystick position data.
  
  See section 10 of the BFF Driver Test App user guide for details of the procedure; it is a simple procedure carried out on each card individually.
   
• Set the BFF CL Software for pot-less operation. This will tell the CL software to read control position data from the driver cards and write it to FS via FSUIPC. The position data is written directly to the FS control offsets WITHOUT additional calibration, as a result the control input to FS is linearly proportional to the drive motor rotational position. Usually (depending on the control mechanics) this also means the control input is linearly proportional to stick position.
  
  To make the settings run the BFF Setup Application and go to the background process settings area by clicking the Bck_Grnd_Set button.  In the "Main Axis Position Reporting" area change the Line74: Position reporting method setting to 1 (one).
  
  Then in the "Processing" settings area check that Line 62: Fixed x10 resolution enable is set to 1 (one).
  
  Save and exit.

In operation the CL software will then check the driver cards for valid firmware and if confirmed will proceed to read control position from the cards (encoders) and write to FS via FSUIPC. A healthy background process loop rate (50 Hz or ideally higher) is required to minimise lag in the FS control movement. If necessary the Line 1: Force loop delay parameter can be reduced to increase the processing rate - but keep it below 100Hz. NOTE: The lag issue has been resolved with V1.25 of the BFF_Cl_Background process.

The changes made to the background process settings apply whenever the CL software runs and so to all aircraft configurations used by the CL Software thereafter.

IMPORTANT If you are swapping an existing system over to "pot-less" operation remember to remove the unused joystick axis assignments in FS. If FS "sees" additional joystick control inputs at the same time as receiving CL position instructions the FS controls will jitter.

Although pot-less operation removes the need for potentiometers on the main control axes, a joystick card will still be required for the trim inputs to the CL system. These can be by pot or by button - see the section 7.

FS control input calibration in "pot-less" mode

When operating in "pot-less" mode the FS control positions are written directly to FS (via FSUIPC) by the CL software - this prevents calibration of the FS control response using the usual gamecontroller or FSUIPC calibration methods. With the BFF_CL_Background process v1.25 or later this calibration can be done within the CL software.

Please use the BFF_CL_Setup_v1.08 application - Go to the background process settings area and use Lines 75 to 77 to set "sensitivity" factors for each of the control axes as required. These factors adjust the movement response of the FS controls to the movement of the real controls - read the pop-up help tips for more details.

The settings can be used to either slow or speed-up the movement of the FS controls with respect to that of the real controls when operating around the mid-point region. 

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