InputTrigger/WheelSpeed (2009-08-07 19:45:54)

VEMS uses the PS2 clock signal to receive 0/5V wheelspeed frequency signal. Became very popular recently.

The PS2 firmware uses the PS2 port for keyboard, and launch-RPM is time-based (not wheelspeed). For wheelspeed input to work, the "non-PS2" firmware must be uploaded ( my_make.16x14/vems.hex ). See GenBoard/UnderDevelopment/FirmwareChanges around and after 1.1.53

Use recent VemsTune.

Sensitive pin

PS2 clock input is a direct CPU pin. It is very sensitive. Either static electricity or 12V will damage the main processor immediately.

Customers are advised to request in the WebShop order note:

With the 5V1 zener it is less likely to damage it, and an open-collector HALL sensor or a VR signal and a simple NPN inverter (same as CamHALLInverter) can be used to drive the signal (LM1815 is not necessary for this, although that would work too). Care is still needed of course.


Wheelspeed data usage


Launchcontrol

The good old initial launch behaviour with retard and launch-enrichment is still there.

But after reaching the first entry in an 8 entry table (array), no retard, no enrichment:

2x8 bytes for wheelspeed => RPMlimit. Firmware uses interpolation for smooth transitions between table-points.

RPMlimit is in 100 RPM unit.

wheelspeed is the unit of your choice. Usually:

The same table is time => RPMlimit for the PS2 firmware where wheelspeed is not available. Time is in 64 msec unit.

The first and last bin in the table are somewhat special:

"Launch RPM vs Road Speed" screen:

VEMSMTRevSpeed.gif

Kevin's note: I have the table/curve in the MegaTune(works in Megatune but not tested on engine yet)

You'll note in the main menu and the [ini] that I have changed many of the titles and have organized the functions differently.

Note: the "launch-active" flag in VemsTune only lights up when the RPM-limit is reached (not when the button is pressed - this can be confusing). So if you want to test an analog input switchbutton, configure the ALS input to that pin to see that it lights up.


Temporary note - for .ini file tweakers.

This section should be cleaned up when these are deployed in both MegaTune and VemsTune 2009-05-xx releases.

Direct commands for page15 (launchcontrol wheelspeed=>launchRPMlimit) read/write are [] brackets.

Check the mct dump to see if s[0]= and s[1]=... values are set as you expect.


REST OF THE PAGE IS BRAINSTORMING


Freq to voltage - could also be used

[LM2917] frequency to voltage converter to get wheelspeed info on the LCD and for logging.

The app note even has a design almost ready for use

Is anyone besides me interested in this?

Is there any problem with this solution that I am missing? //Emil