brake data

i have 2 sets of brake data. 1) brake on/off. 2) some sort of brake pressure.

1) brake on/off i have a can-bus pid that flips a single bit when the brake pedal is pressed any amount
2) i have a value that decreases as the brake it pressed. i assume this is brake pressure, but still unsure of the units

Trying to use #1 for now, until i figure out the pressure PID, but the on/off solution when rendering overlay is weird. it appears that the overlay is interpolating my values, either 0 or 100 (brake off or brake on) and draws the animated from 0 to 100 and 100 to 0. is there anyway to turn off the interpolation? either in the RaceChrono interface or by sending data to represent on/off?

For #2, once i have figure out brake pressure PID units, it seems like the PID editor is expecting kPa as unit. but absolute pressure values can differ car to car, so what does Racechrono use for brakes off and maximum brake when using pressure?



  • edited September 8
    No way to turn off the interpolation at the moment. The RaceChrono "core" allows it but no way to configure in UI at the moment ...

    All pressure channels take kPa as units, as it is the internal units in RaceChrono, but you can put multipliers to convert from whatever the source units are to kPa. RaceChrono then displays the values in the pressure units are which are configured in settings.

    Digital 0 and 100 works for on/off, but as you have brake pressure available, why not make it scale between 0-100? Just figure out the pressure of the reasonable full braking. Then anything over that should be 100. And anything less should be scaled between 0 and 100.
  • yea, makes sense regarding scaling the brake pressure. thanks!

    since in the DIY device case, unlike the off-the-shelf OBD-II adapter case, does it make sense to scale the values in the arduino if there are plenty of cpu cycles available? its certainly an option in the DIY when you control the code to both the CAN-bus device and RaceChrono channels.

    or is a modern iPhone fast enough that having a bunch of RaceChrono equations like scale(bytesToUIntLe(raw, 5, 2)), XXX, YYY, 0, 100) and doing that sort of evaluation not really an issue for RaceChrono? if one was doing 6-10 data points at 10-50 hz? plus 25 hz RaceBox Mini?
  • RaceChrono solves the equations very efficiently, so there is virtually no overhead from this. Also modern phones have very fast processors and multiple cores.
  • My personal suggestion here would be to transmit the data as-is from the car to the phone, and map the binary data to "real" data using RaceChrono equations.
    Every once in a while you'll find that your multiplier for brake data is off (either too high, causing >100% values, or too low, where the highest values are way below 100%), and will want to tweak it.
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