Time multiplexed control of air core gauges from a microprocessor address/data bus

• US 4,875,041 A
• Filed: 11/21/1988
• Issued: 10/17/1989
• Est. Priority Date: 11/21/1988
• Status: Expired due to Term

• Current Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Original Assignee: Navistar International Transportation Corp. (Volkswagen AG)
• Inventors: Dannenberg, Robert D.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Queen, Tyrone
• Application Number:
  US07/274,094
• Time in Patent Office: 330 Days
• Field of Search: 340/870.01, 340/870.11, 340/870.13, 340/825.07, 340/825.06, 340/459, 340/461, 340/462, 340/700, 307/10.1, 364/424.01, 364/424.03, 364/424.04, 364/424.05, 364/579, 364/580, 370/58, 370/77, 370/85, 33/178 E
• US Class Current: 340/870.13
• CPC Class Codes: B60R 16/0315 using multiplexing techniques multiplexing for transmission of signals G08C15/00; multiplexing for electrical communication in general H04J
• CPC Class Codes: G08C 15/06 successively, i.e. using time division

Abstract

An instrumentation system in which air core gauges are adapted for use with a microprocessor that provides data for the gauges in digital form via an address/data bus. One of the principal features of the invention is that minimum circuitry interfaces the microprocessor with the air core gauges. Each gauge is assigned to a particular output device on the microprocessor memory map. The microprocessor addresses a particular gauge via the address bus at the same time that data for the gauge is present on the data bus. Each gauge comprises a sample and hold circuit and an air core driver circuit which operate the gauge'"'"'s air core meter. The sample and hold circuits share a common digital-to-analog (D/A) converter which is interposed between the digital data bus and the sample and hold circuits. A meter selection logic circuit receives address information from the microprocessor and causes the analog information from the D/A converter to be sampled and held by the particular gauge that is identified by the particular address being supplied to the meter selection logic. Each sample and hold circuit holds the information that has been multiplexed to it to thereby provide a continuous output signal to the associated driver circuit which in turn drives the air core meter movement to a corresponding deflection that indicates the value of the data that is in its sample and hold circuit.

Claims

1. In an instrumentation system in which data representing the values of various parameters of interest is presented to a central processing unit (CPU), and the CPU processes the data presented to it and in turn intermittently presents the data for each parameter of interest as a multi-bit value on a multi-bit digital data bus, the improvement for displaying the data for each parameter of interest via the air core meter movement of a corresponding gauge by addressing each gauge via an address bus when data for the gauge is present on the data bus, said improvement comprising:

(a) a digital-to-analog converter circuit that is shared by all gauges, said digital-to-analog converter circuit having an input and an output, the input of said digital-to-analog converter circuit being coupled to the data bus;

(b) gauge selection means having an input coupled to the address bus and a plurality of outputs each of which is connected to a corresponding gauge, said gauge selection means comprising means for selectively activating its outputs in accordance with addresses supplied to it via the address bus so as to enable each gauge to be selectively activated to receive data;

(c) each gauge comprising a sample and hold circuit having a first input coupled to the digital-to-analog converter circuit output and a second input coupled to a particular one of the gauge selection means outputs, each sample and hold circuit comprising means for causing the signal at its first input to be sampled and to be held at an output thereof when its second input is activated by said gauge selection means; and

(d) each gauge further comprising a driver circuit having an input that is coupled to the output of its sample and hold circuit and an output by which the movement of its air core meter is operated.

2. The improvement set forth in claim 1 in which the driver circuit of at least one of said gauges comprises a sine/cosine air core driver circuit and the air core meter thereof comprises a sine/cosine meter.

3. The improvement set forth in claim 1 in which the driver circuit of at least one of said gauges comprises a unity gain amplifier circuit and the air core meter thereof comprises a sensor-driven meter.

4. For use in an instrumentation system in which data representing the values of various parameters of interest is presented to a central processing unit (CPU), the CPU processing the data presented to it and in turn intermittently presenting the data for each parameter of interest as a multi-bit value on a multi-bit digital data bus, the data for each parameter of interest being displayed via the air core meter movement of a corresponding gauge by addressing each gauge via an address bus when data for the gauge is present on the data bus, a digital-to-analog converter circuit being shared by all gauges, said digital-to-analog converter circuit having an input and an output, the input of said digital-to-analog converter circuit being coupled to the data bus, and gauge selection means having an input coupled to the address bus and a plurality of outputs each of which is connected to a corresponding gauge and comprising means for selectively activating its outputs in accordance with addresses supplied to it via the address bus so as to enable each gauge to be selectively activated to receive data an improved gauge comprising:

(a) a sample and hold circuit having a first input for coupling to the digital-to-analog converter circuit output and a second input for coupling to a particular one of the gauge selection means outputs, said sample and hold circuit comprising means for causing the signal at its first input to be sampled and to be held at an output thereof when its second input is activated by said gauge selection means; and

(b) further comprising a driver circuit having an input that is coupled to the output of its sample and hold circuit and an output by which the movement of its air core meter is operated.

5. A gauge as set forth in claim 4 in which the driver circuit of said gauge comprises a sine/cosine air core driver circuit and the air core meter thereof comprises a sine/cosine meter.

6. The improvement set forth in claim 4 in which the driver circuit of said gauge comprises a unity gain amplifier circuit and the air core meter thereof comprises a sensor-driven meter.

7. For use in a gauge of an instrumentation system in which data representing the values of various parameters of interest is presented to a central processing unit (CPU), the CPU processing the data presented to it and in turn intermittently presenting the data for each parameter of interest as a multi-bit value on a multi-bit digital data bus, the data for each parameter of interest being displayed via the air core meter movement of a corresponding gauge by addressing each gauge via an address bus when data for the gauge is present on the data bus, a digital-to-analog converter circuit being shared by all gauges, said digital-to-analog converter circuit having an input and an output, the input of said digital-to-analog converter circuit being coupled to the data bus, and a gauge selection means having an input coupled to the address bus and a plurality of outputs each of which is connected to a corresponding gauge and comprising means for selectively activating its outputs in accordance with addresses supplied to it via the address bus so as to enable each gauge to be selectively activated to receive data an improved gauge circuit means comprising:

(a) a gauge circuit for operating the movement of its air core meter comprising a sample and hold circuit having a first input for coupling to the digital-to-analog converter circuit output and a second input for coupling to a particular one of the gauge selection means outputs, said sample and hold circuit comprising means for causing the signal at its first input to be sampled and to be held at an output thereof when its second input is activated by said gauge selection means; and

(b) a driver circuit having an input that is coupled to the output of said sample and hold circuit and an output by which the movement of its air core meter is operated.