Touchpad pen-input controller

• US 5,883,622 A
• Filed: 01/17/1997
• Issued: 03/16/1999
• Est. Priority Date: 01/17/1997
• Status: Expired due to Fees

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Tritech Microelectronics International Pte LTD
• Inventors: Lim, Swee Hock Alvin, Ong, Eng Yue, Ng, Maisy Mun Lan, Chan, Chow Fong, Geng, Xia
• Primary Examiner(s): Luu, Matthew
• Application Number:
  US08/785,738
• Time in Patent Office: 788 Days
• Field of Search: 345/156, 345/157, 345/173, 345/174, 345/175, 345/211, 345/212, 178/18, 178/19
• US Class Current: 345/173
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• CPC Class Codes: G06F 1/3215 Monitoring of peripheral devices

Abstract

Systems and methods for the detection of motions of a pointed object upon a writing surface such as a touchpad is disclosed. The motions will be detected and converted in a multiplexing analog-to-digital converter to digital codes representing the location of the pointed object and the pressure of the pointed object upon the touchpad. The location and the pressure will be translated into a pen detect signal indicating the presence of the pointed object upon the touchpad. The digital codes will be averaged to minimize noise created by vibrations and variations in the motions of the pointed object held by the human hand and formed into an absolute coordinate digital code. The absolute coordinate digital code, the pressure digital code, and the pen detect signal will be converted to a touchpad-computer interface protocol for transmission to a computer system for further processing. The pen detect signal will be sense to determine if the pointed object has not been in contact with the touchpad for a long period of time and remove power from the circuitry controlling the touchpad. For battery power operations, a battery sense line will be connected to the multiplexing analog-to-digital converter to create a battery power set of digital codes which are manipulated in a battery gauge circuit to create a battery condition set of digital codes which are transmitted to the computer system.

Claims

1. A battery powered touchpad digitizing computer input device to detect a presence of a pointed object upon a surface and converting said presence to a set of digital codes that indicate location and force of said pointed object upon said surface, comprising

a) a touchpad digitizer having a hard covering surface, a touch input transducer to convert said presence to electrical responses proportional to a distance of said pointed object from peripheral sides of said surface and proportional to the force of said pointed object upon said surface;

b) a touchpad driver circuit connected to said touchpad digitizer to provide an electrical stimulus to said touch input transducer;

c) a pressure sense circuit to convert the electrical responses to a pressure analog signal proportional to said force of the pointed object upon said surface;

d) a multiplexing analog-to-digital converter to accept a plurality of analog signals including the electrical responses and the pressure analog signal, and convert said plurality of analog signals to a plurality of digital codes that include a set of location digital codes representing the location of the pointed object upon the surface and a set of pressure digital codes representing the force of the pointed object upon the surface;

e) a pen detect circuit that receives the electrical responses when said pointed object has been placed upon said touchpad digitizer;

f) a touchpad computer interface connected to the multiplexed analog-to-digital converter and the pen detect circuit to receive and convert the location digital codes, the set of pressure digital codes, and the pen detect signal to a touchpad-computer interface protocol that contains an absolute location and pressure of said pointed object upon said touchpad digitizer and to transmit said protocol to a computer system for further processing,

g) a battery to provide a voltage and a current to said touchpad digitizing computer input device and to said computer system, wherein said battery has a battery sense line that is included as one of the plurality of analog signals connected to said multiplexing analog-to-digital converter, and is converted to a set of battery power digital codes indicating the level of the voltage and the current,

h) a battery gauge circuit to calculate from the battery power digital codes, a battery condition set of digital codes, which indicates a charging state of said battery, and to transmit said battery condition set of digital codes to the touchpad interface, wherein said touchpad-computer interface will transmit said battery condition set of digital codes to said computer system;

i) a power supply control and regulator circuit connected to said battery to control and regulate the voltage and the current to said battery powered touchpad digitizing computer input device; and

j) an autopower save circuit connected to the pen detect circuit to receive the pen detect signal, to interpret said pen detect signal to determine if said pointed object has not been in contact with the touchpad surface for a long period of time, and to create an autopower down signal that will be transferred to the power supply control and regulator circuit to command removal of the voltage and current from said battery powered touchpad digitizing computer input device and to restore said voltage and current if the pen detect signal indicates that the pointed object is in contact with the touchpad surface.

2. The input device of claim 1 wherein the electrical responses varies in magnitude according to the location of said pointed object upon said touchpad.

3. The input device of claim 1 wherein the pointed object is selected from the set of pointed objects including a human finger, a stylus, and a pen.

4. The input device of claim 1 wherein the electrical response selected from the set of electrical responses that include a change in voltage, a change in current, and a change in frequency of an oscillating signal.

5. A touchpad digitizer computer input device control circuit to accept electrical response signals generated by a pointed object in contact with a touchpad digitizer, and to create an absolute coordinate set of digital codes, a pressure magnitude set of digital codes and a pen detect signal for transmission to a computer system for placement of a cursor upon a display screen, to signal an end of stroke in handwriting recognition programs, and to provide stroke, location, and pressure information to signature entry and verification programs, comprising:

a) a touchpad driver circuit connected to said touchpad digitizer to provide an electrical stimulus to said touch input transducer;

b) a pressure sense circuit to convert the electrical responses to a pressure analog signal proportional to said force of the pointed object upon said surface;

c) a multiplexing analog-to-digital converter to accept a plurality of analog signals including the electrical responses and the pressure analog signal, and convert said plurality of analog signals to a plurality of digital codes that include a set of location digital codes representing the location of the pointed object upon the surface and a set of pressure digital codes representing the force of the pointed object upon the surface;

d) a pen detect circuit that receives electrical responses to create a pen detect signal when said pointed object has been placed upon said touchpad digitizer; and

e) a touchpad computer interface connected to the multiplexed analog-to-digital converter and the pen detect circuit to receives and converts the location digital codes, the set of pressure digital codes, and the pen detect signal to a touchpad-computer interface protocol that contains an absolute location and pressure of said pointed object upon said touchpad digitizer and to transmit said protocol to a computer system for further processing.

6. The control circuit of claim 5 further comprising a power supply control and regulator circuit connected to a power source to control and regulate the voltage and the current to the touchpad digitizer computer input device control circuit.

7. The control circuit of claim 5 further comprising an autopower save circuit connected to the pen detect circuit to receive the pen detect signal, to interpret said pen detect signal to determine if said pointed object has not been in contact with the touchpad surface for a long period of time, and to create an autopower down signal that will be transferred to the power supply control and regulator circuit to command removal of the voltage and current from the touchpad digitizer computer input device control circuit and to restore said voltage and current if the pen detect signal indicates that the pointed object is in contact with the touchpad surface.

8. The control circuit of claim 5 wherein the plurality of analog signals connected to said multiplexed analog-to-digital converter further comprises a power sense signal connected to the power source that will provide said voltage and current to the touchpad digitizer computer input device control circuit and to the computer system.

9. The control circuit of claim 8 wherein said multiplexed analog-to-digital converter will convert said power sense signal to a set of power digital codes indicating the level of the voltage and the current of said power source.

10. The control circuit of claim 9 further comprising a power gauge circuit to calculate from the power digital codes, a power condition set of digital codes, which indicates a charging state of said power source, and to transmit said power condition set of digital codes to the touchpad interface, wherein said touchpad-computer interface will transmit said power condition set digital codes to said computer systems.

11. The input device of claim 5 wherein the electrical responses varies in magnitude according to the location of said pointed object upon said touchpad.

12. The input device of claim 5 wherein the pointed object is selected from the set of pointed objects including a human finger, a stylus, and a pen.

13. The control circuit of claim 5 wherein the electrical response selected from the set of electrical responses that include a change in voltage, a change in current, and a change in frequency of an oscillating signal.

14. A method to determine movements of a pen upon a surface of a digitizing touchpad and transferring digital codes reflecting the movements to a computer system, comprising the steps of:

a) deactivating a power down signal and reapplying electrical power to a touchpad pen-input controller;

b) detecting electrical responses to movements of a pointed object upon the surface of a digitizing touchpad;

c) if the pointed object is detected upon the surface of the digitizing touchpad, converting the detected electrical responses to the movements in a multiplexing analog-to-digital converter to a set of location digital codes indicating location of the pointed object upon the surface of the touchpad;

d) converting the detected electrical responses to a pressure sense analog signal;

e) converting the pressure sense analog signal in the multiplexing analog-to-digital converter to a set of pressure digital codes indicating the amount of force the pen is exerting upon the digitizing touchpad surface;

f) creating a pen detect signal that indicates the presence of the pointed object upon the surface of the touchpad from the electrical responses;

g) averaging to minimize noise effects to create a set of absolute coordinate digital codes that are a more consistent indication of the movement of the pointed object upon said touchpad digitizer, and forming a set of absolute location digital codes from the location digital codes that indicates the coordinate position of the pointed object upon the digitizing touchpad

h) converting the pen detect signal, the absolute location digital codes, and the set of pressure digital codes to a touchpad-computer interface protocol; and

i) If the pen detect signal indicates the pointed object is on the surface of the digitizing touchpad, transmitting the touchpad-computer interface protocol to the computer system for further processing.

15. The method of claim 14 further comprising removing of power from the circuitry that will implement this method so as to conserve energy whenever the pointed object has not been detected as being present on the digitizing touchpad for a period of time, and restoring power to the circuitry whenever the pointed object is detected as touching the digitizing touchpad.

16. The method of claim 14 wherein the detecting of the movements is an electrical response from said touchpad created by and electrical stimulus from a touchpad driver.

17. The method of claim 14 wherein the converting of the detected movements is a conversion of the electrical response in a multiplexing analog-to-digital converter to the location set of digital codes.

18. The method of claim 14 wherein the electrical response varies in magnitude according to the location of said pointed object upon said touchpad.

19. The method of claim 14 wherein the electrical response is selected from the set of electrical responses that include a change in voltage, a change in current, and a change in frequency of an oscillating signal.

20. The method of claim 14 wherein the pointed object is selected from the set of pointed objects including a human finger, a stylus, and a pen.