Calibration in PurrOS — step by step

Calibration sets each pedal’s full range of travel. Do it in PurrOS, on the Input settings tab, one pedal at a time.

Before you start

Download PurrOS from fatblackcat.io/downloads and install it. PurrOS detects your pedals automatically, so you can connect them and their power supplies either before or after you open the application. See cabling: the correct order.

Where do I calibrate?

Click your set’s tile on the Home screen, or the Quick access shortcut, to open the pedal settings page, and stay on the Input settings tab.

You’ll see Clutch / Brake / Throttle sections (clutch inactive until the clutch pedal ships). A section with no pedal connected shows Not Connected.

How do I calibrate a pedal?

1. Make sure the pedal is fully released and do not touch it. Click Calibrate in the pedal’s column to open the dialog.
2. About a second after the dialog opens, PurrOS records the released position automatically, whatever position the pedal is in. A slightly pressed pedal would be saved as released.
3. Follow the prompts: press fully and hold, release again, then press fully again. Wait for each next step to appear before you move.
4. When “Calibration capture complete” appears, review the captured range and click Save. Save stays disabled until all the steps are done and a valid range has been captured. Save keeps the calibration in your profile in PurrOS; click Send to device to send it to the pedals.

The dialog is titled for the pedal, for example Calibrate brake. Its status line reports progress and the live raw value shows on the bar below. If anything looks wrong, Reset restarts the capture; Cancel discards it.

Important: because of the Active Heel Support and the weight of your leg, do not rest your heel on the heel rest during calibration. Press the pedal using only the pedal face.

What does Save do, and when do I need Send to device?

Save in the Calibrate dialog only updates the profile in PurrOS. It does not send anything to the pedals. Once the pedals have the calibration, they store it permanently: it survives power cycles, but not a firmware update.

Changes to calibration, deadzones, curves and Max force reach the pedals when you click Send to device. A few actions send straight away: the deadzone keyboard shortcuts, Save in the full-screen calibration window (opened with its keyboard shortcut), and Save in the unsaved-changes prompt.

To send your changes and see confirmation that the pedals received them, click Send to device. The button shows Sending…, then turns green with Sent to device. See Send to device: what the button shows and what greyed out means.

Deadzones, Min and Max, and maximum brake force

• Min and Max hold the captured raw sensor values, and Raw shows the live reading, so you can check the pedal responds across its whole travel. You can set Min and Max with the arrows or type the values in directly.
• Deadzones: set a Bottom and a Top deadzone for each pedal, from 0 to 25%. A Bottom deadzone ignores the first part of the travel; a Top deadzone lets you reach 100% before the end of the travel.
• Max force (brake): sets the pedal force at which the brake reaches 100% output, anywhere from 15 to 195 kg. The brake uses a 200 kg load cell with 195 kg max braking force; set Max force lower and you reach full braking at that figure instead. Show brake force in kilograms switches the live readout between kilograms and percent; it does not change the graph scale.

Calibration can also be done manually, by typing values into the Min and Max fields. The same applies to the deadzone fields.

Response curves and Favorites

Each pedal has its own response curve on its Input settings card. The curve has 11 points. On the throttle the two end points are fixed and the nine inner points can be dragged; on the brake the 100% end point can also be dragged along the Y axis. A curve bent below the diagonal gives finer control at the start of the travel; above it, a more aggressive initial response.

Favorites keeps up to five curves per pedal. Double-click a tile to apply its curve, use the save icon to overwrite the selected tile with the current curve, and the bin icon to clear it. Favorites are shared across all your profiles.

Profiles

Use the profile bar at the top of the pedal settings page to save your settings as profiles, for example one per sim or car, and to export or load them.

Do I calibrate again in the game?

In games you should usually only do the initial calibration of the pedals, as in iRacing. All settings and characteristics can then be changed in PurrOS. See in-game calibration: do it once, full range.

Set-and-forget

Calibration lives on the pedal’s chip. You can close PurrOS entirely while racing. A firmware update resets calibration, deadzones, response curves and axis inversion to factory defaults, so after an update select your saved profile and press Send to device, or recalibrate. See PurrOS firmware updates.

Related articles

PurrOS 2.0: what it does, Send to device: what the button shows and what greyed out means, Pedals behave wrong in ACC / LMU / ACE.