Apparatus to sense stylus nib pressures

1. A stylus comprising:

a deformable bladder filled with at least one gas; and

at least a first pressure sensor responsive to pressure changes in the deformable bladder, the pressure changes capable of being processed to provide force signals representing a forces applied to a stylus nib as comprises a part of the stylus.

2. The stylus of claim 1 wherein the first pressure sensor is configured to sense a deformable bladder gas pressure that corresponds to force being applied to the stylus nib.

3. The stylus of claim 2 further comprising:

at least a second pressure sensor disposed within the stylus and configured to sense ambient air pressure.

4. The stylus of claim 3 further comprising:

a control circuit operably coupled to the first and second pressure sensor and configured to determine a gauge pressure value as corresponds to force being applied to the stylus nib.

5. The stylus of claim 4 further comprising:

a temperature sensor operably coupled to the control circuit;

wherein the control circuit is configured to use temperature information from the temperature sensor when determining the gauge pressure value.

6. The stylus of claim 5 further comprising:

a mechanical stop to prevent the deformable bladder from deforming beyond a given amount of deformation.

7. The stylus of claim 6 wherein the mechanical stop includes electrically-conductive surfaces that complete an electric circuit when the deformable bladder reaches the given amount of deformation.

8. The stylus of claim 1 wherein the deformable bladder

is configured to deform in response to application of the force to the stylus nib and that is pneumatically coupled to the first pressure sensor.

9. A force-sensitive stylus comprising:

a barrel;

a nib;

a first pressure sensor disposed within the barrel and configured to sense an air pressure that corresponds to force being applied to the nib;

a second pressure sensor disposed within the barrel and configured to sense ambient air pressure;

a control circuit operably coupled to the first and second pressure sensor and configured to determine a gauge air pressure value corresponding to force being applied to the nib.

10. The force-sensitive stylus of claim 9 further comprising:

an air bladder that deforms in response to force being applied to the stylus nib and that is pneumatically coupled to the first pressure sensor.

11. The force-sensitive stylus of claim 10 further comprising:

a mechanical stop configured to prevent the air bladder from deforming beyond a given amount of deformation.

12. The force-sensitive stylus of claim 11 wherein the mechanical stop includes a cap disposed over at least a part of the air bladder.

13. The force-sensitive stylus of claim 12 wherein the cap is comprised, at least in part, of electrically-conductive material.

14. The force-sensitive stylus of claim 13 further comprising:

at least two electrically-conductive traces disposed to contact the cap when the cap stops further deformation of the air bladder such that the electrically-conductive material completes an electrical circuit to thereby provide a corresponding signal.

15. A force-sensitive stylus comprising:

a barrel;

a nib;

a first pressure sensor disposed within the barrel and having a gas-filled bladder configured to sense a pressure that corresponds to a force being applied to the nib over a nib force range such that a bladder volume as corresponds to the gas-filled bladder aligns the nib force range with a sensor pressure range for the first pressure sensor;

a second pressure sensor disposed within the barrel and configured to sense ambient air pressure;

a control circuit operably coupled to the first and second pressure sensor and configured to determine a gauge air pressure value corresponding to force being applied to the nib.