Computing device with haptic trackpad

A method for adjusting a driving signal for a haptic trackpad in a computing device, the method comprising:

• driving a haptic actuator in the computing device with the driving signal to cause a trackpad acceleration in the trackpad;
• measuring the trackpad acceleration using a signal from an accelerometer in the computing device;
• determining an acceleration variance by comparing the trackpad acceleration to a target acceleration;
• and
• using the acceleration variance to adjust the driving signal for the haptic actuator to an adjusted driving signal.

A computing device, comprising:

• a trackpad comprising a printed circuit board;
• an accelerometer affixed to the printed circuit board;
• a haptic actuator coupled to the trackpad;
• a processor;
• and
• a memory storing instructions executable by the processor to:
• receive a first touch input at a selected subregion in an array of subregions of a touch surface of the trackpad;
• determine a touch force of the first touch input;
• at least on condition that the touch force exceeds a threshold touch force, use a driving signal associated with the selected subregion to drive the haptic actuator to cause a first trackpad acceleration in the trackpad;
• measure the first trackpad acceleration using a signal from the accelerometer;
• determine an acceleration variance by comparing the first trackpad acceleration to a target acceleration;
• use the acceleration variance to adjust the driving signal associated with the selected subregion to an adjusted driving signal;
• receive a second touch input at the selected subregion in the array of subregions of the touch surface;
• and
• at least on condition of receiving the second touch input at the selected subregion, drive the haptic actuator with the adjusted driving signal to cause a second trackpad acceleration in the trackpad different from the first trackpad acceleration.