Telemetry encoding technique for smart stylus

• US 6,441,810 B1
• Filed: 10/31/1995
• Issued: 08/27/2002
• Est. Priority Date: 10/31/1995
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Skoog, Steven K., Tabor, Gregory A.
• Primary Examiner(s): LAO, LUNYI
• Application Number:
  US08/551,303
• Time in Patent Office: 2,492 Days
• Field of Search: 345/179, 345/173, 345/174, 345/175, 345/180, 345/181, 345/182, 345/183, 178/18-20, 178/87, 178/18.01, 178/18.02, 178/18.03, 178/18.07, 178/19.01, 178/19.03, 178/20.03
• US Class Current: 345/179
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

The invention relates to the transmission of telemetry data from a stylus to a host computer via a serial, asynchronous data channel. The telemetry data is encoded into code-words using a specially selected error detecting or error correcting code, the code-words are transmitted from the stylus in a continuous, homogeneous data stream without the use of framing delimiters between adjacent code-words, and the code-words are then received by the host computer which separates the code-words according to the unique characteristics of the selected code. The code may be chosen based on both the error detection/correction requirements of the system and the probability that the code will create invalid intermediate code matches between consecutive back-to-back code-words. In one embodiment, the invention provides a synchronization scheme which greatly reduces the probability that invalid intermediate code matches will be recognized in the host computer as validly transmitted code-words.

Claims

1. The method, as claimed in claim 1, wherein:

said step of selecting a code includes selecting a code based on the probability that invalid, intermediate matches will be formed between back-to-back code-words.

2. The method, as claimed in claim 1, wherein:

said code-words include a data portion and a code portion.

3. The method, as claimed in claim 2, further comprising the step of:

further encoding said code-words using a code which imparts timing information to said continuous stream of packets.

4. The method, as claimed in claim 2, wherein:

said selected code includes one of the following;

an error detecting code and an error correcting code.

5. The method, as claimed in claim 4, further comprising the steps of:

detecting errors in said code-words after said step of separating; and

rejecting code-words which contain errors.

6. The method, as claimed in claim 2, wherein:

said step of encoding includes encoding said input data words using a shortened (23,12) Golay code which may be generated using a 5343₈ generator polynomial.

7. The method, as claimed in claim 6, wherein:

said step of encoding further includes inverting a portion of said Golay coded data words using a 3775₈ inversion which comprises inverting every bit of said portion except a second to last bit.

8. The method, as claimed in claim 2, wherein:

said step of transmitting said code-words includes modulating a carrier signal using said continuous stream of packets and emitting said modulated carrier signal from said stylus.

9. The method, as claimed in claim 8, wherein:

said step of receiving includes receiving said modulated carrier signal from said stylus and removing said carrier signal component to produce said continuous stream of packets.

10. The method, as claimed in claim 2, wherein:

said step of separating said continuous stream of packets includes the step of recognizing valid code-words in said continuous stream of packets.

11. The method, as claimed in claim 10, wherein:

said step of recognizing valid code-words in said continuous stream of packets includes the step of only checking certain positions in said continuous stream of packets for a valid code-word after a predetermined number of valid code-words have been recognized at specific positions in said stream of packets, to effectively reject invalid intermediate code-matches.

12. The method, as claimed in claim 10, wherein:

said step of separating said continuous stream of packets further includes the step of qualifying each recognized valid code-word based on whether a predetermined number of valid code-words have been recognized at specific positions in said stream of packets.

13. The method, as claimed in claim 1, further comprising the step of:

further encoding said code-words using a code which creates a DC balanced stream of packets.

14. The apparatus, as claimed in claim 1, wherein:

said encoding means includes a linear feedback shift register circuit.

15. The apparatus, as claimed in claim 1, wherein:

said means for separating includes exclusive-OR tree circuitry.

16. The stylus, as claimed in claim 1, wherein:

said means for encoding further includes means for inverting a portion of each of said Golay coded data words using a 3775₈ inversion which comprises inverting every bit of said data words except a second to last bit.

17. In a computer system having a stylus that delivers telemetry data to a host computer via a continuous, uninterrupted stream of back-to-back code-words, an apparatus for receiving said continuous, uninterrupted stream of back-to-back code-words from said stylus and for accurately separating said code-words for use by said host computer, said apparatus comprising:

code checking means for monitoring said continuous, uninterrupted stream of back-to-back code-words and for detecting the occurrence of bit strings in said stream which match valid code-words; and

synchronization means for qualifying detected bit-strings which match valid code-words based on whether a predetermined number of bit-strings have been detected by said code checking means at specific positions in said continuous stream of back-to-back code-words, said qualified detected bit-strings being output for use by said host computer.

18. The apparatus, as claimed in claim 17, wherein:

said synchronization means further comprises;

means for instructing said code checking means to only check for the occurrence of bit strings which match valid code-words at certain positions in said continuous stream of back-to-back code-words after a predetermined number of bit strings which match valid code-words have been detected at specific positions in said stream, to effectively reject invalid intermediate code-matches.