Vehicle communications network transceiver, bus driver therefor

• US 5,363,405 A
• Filed: 11/27/1992
• Issued: 11/08/1994
• Est. Priority Date: 11/27/1992
• Status: Expired due to Term

• Current Assignee: Chrysler Group LLC (Stellantis NV)
• Original Assignee: Chrysler Corporation (Stellantis NV)
• Inventors: Hormel, Ronald F.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US07/982,321
• Time in Patent Office: 711 Days
• Field of Search: 375/5, 375/22, 375/7, 375/36, 370/85.8, 370/85.2, 340/425.5, 340/825.08, 340/310 A, 340/825.57, 340/825.63, 329/312, 332/109, 307/9.1, 307/10.1, 341/53
• US Class Current: 375/219
• 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: H03K 7/08 Duration or width modulation ; Duty cycle modulation
• CPC Class Codes: H03K 9/08 of duration- or width-mudulated pulses or of duty-cycle modulated pulses
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H04L 2012/40273 the transportation system being a vehicle
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/0278 Arrangements for impedance matching
• CPC Class Codes: H04L 25/0286 Provision of wave shaping within the driver wave shaping per se H04L25/03834
• CPC Class Codes: H04L 25/0292 Arrangements specific to the receiver end
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

A transceiver device for use with a microcontroller and a symbol encoder decoder device (forming a node in a communications network) for transmitting and receiving variable pulse width modulated (VPWM) analog signals containing symbol messages over a communications bus. The transceiver accepts digital VPWM signals from the symbol encoder decoder device which were generated by the microcontroller and converts the digital signals into VPWM analog signals and then transmits the analog signal over the bus to other nodes. The transceiver also receives VPWM analog signals placed on the bus by other nodes of the network and transfers the signals in digital form to the symbol encoder decoder device which, in turn, communicates the decoded messages to the microcontroller. The transceiver contains a ground translation circuit for transferring transmitted signals to an independent bus ground return before a bus driver circuit sources message signals in the form of pulse currents over the bus. The bus driver circuit contains circuits that permit arbitration to take place when more than one node attempts to transmit over the bus. The receiver circuit also contains ground translation circuits for translating bus signals from the bus ground return to a signal ground return.

Claims

1. A transceiver in nodes of a multiple node vehicle communications network having a communications bus prescribed for use in an automotive industrial standard data link, interconnecting the nodes, each node providing an input device for converting a chosen measurand into digital pulses appearing at varying rates in response to changes of the measurand into symmetrical, variable pulse width modulated (VPWM) trapezoidal shaped waveform signals, the waveform signals containing symbol information expressing the magnitudes of the measurand, each node containing a regulated power source connected to a vehicle battery to provide regulated logic voltages referenced with respect to a signal ground return;

each node also containing a microcontroller (MCU) connected between the input device, power source and a symbol encoder decoder (SED), for receiving digital pulses from the input device representing magnitudes of the measurands, formatting the received digital pulses into digital messages, polling input and output ports connected to the SED, and initiating transmission over the bus via the SED, the SED being interconnected between the MCU and the transceiver for translating the digital messages from the MCU into said VPWM square-wave, line codings sent to other transceivers connected to the bus and for converting square wave digital signals received from other transceivers into digital messages used by the MCU for updating or controlling other peripherals associated with the network, said transceiver comprising;

(a) an integrator with an input for receiving the VPWM square-wave pulses from SED having pulse widths that define symbol information with respect to time and logic levels, and producing at an output terminal trapezoid type waveform signals with pulses 180 degrees out of phase with the square wave pulses and referenced with respect to a fixed voltage level;

(b) a waveshaper having an input for receiving the trapezoid waveform signals from the integrator and reshaping both corners at the extremities of each edge of the pulses over a chosen duration and then producing at an output terminal other trapezoid waveform signals in phase with the input waveform signals having the same pulse width as the input trapezoid signals at trip point voltages so as to retain the symbol information contained in the original square-wave signals, the reshaped trapezoid signals being referenced with respect to another fixed voltage level different from signal ground;

(c) a voltage-to-current converter having an input for receiving the reshaped trapezoid waveform signals from the waveshaper, and providing at an output a replica of the reshaped trapezoid waveform signals used as control current source signals, said control current source signals being routed to a current sensor circuit within the voltage-to-current converter to provide pulse voltage potentials with respect to signal ground return of magnitudes proportional to the voltage across the current sensor;

(d) a ground translation circuit including a current mirror circuit having an input connected to the current sensor circuit of the voltage-to-current converter so that the current in an input circuit corresponds with the current flowing through the current sensor of the voltage-to-current converter, the ground translation circuit having an output circuit connected to carry a reflected current of the same magnitude and direction as the current in the current mirror input circuit but the output current is referenced with respect to an independent bus ground return, the ground translation circuit also having an output reference voltage circuit used to establish a reference voltage signal referenced with respect to the independent ground return but which establishes voltage levels in response to varying current signals from the output circuit of the current mirror;

d) a bus driver connected between the battery of the vehicle and the independent bus ground return, the bus driver comprising another current mirror circuit having an input circuit used to receive pulse signals from the reference voltage circuit of the ground translation circuit and for using the received pulse signals to program the current in an output circuit of the another current mirror, the programmed current causing a reflected current of an enhanced magnitude and of the same direction as the reference voltage and current to flow out of the output circuit of the another current mirror circuit, the bus driver having an output circuit connected between the output of the another current mirror and the bus for sourcing current onto the bus when the bus voltage levels permit transmitting and for cutting off the source current from the current mirror when the bus voltage levels inhibit transmitting; and

(e) a receiver circuit interconnected between the bus and SED for receiving reshaped trapezoid waveform signals from the bus and extracting symbol information contained in the waveform signals and converting the extracted symbol information into digital pulse signals with pulse durations equivalent to the symbol information.

2. Apparatus as defined in claim 1 wherein the communications bus is a single wire bus.

3. Apparatus as defined in claim 1 wherein the symbol information remains constant in the reshaped trapezoid waveform signals received by each receiver in each transceiver despite the fact that the symbol information in the reshaped trapezoid pulses relates to the independent ground returns in each node and wherein the reference voltage and current in each node bring unaffected by the voltages and currents appearing on the single wire bus.

4. Apparatus as defined in claim 1 wherein the integrator includes circuits for lengthening the rise and fall times of the edges of the input square wave pulses, to produce symmetrical rise and fall time slopes about a chosen maximum pulse amplitude location, and wherein the amplitudes of the pulses being bounded at chosen voltage levels.

5. Apparatus as defined in claim 4 wherein the waveshaper provides gain and controlled gain reduction operations so as to further round the corners of the pulses at the extremities of each edge in forming the reshaped trapezoid pulses and wherein the provided gain produces bounding of the pulses at a chosen voltage amplitudes greater than the amplitudes of the bounded pulses from the integrator.

6. Apparatus as defined in claim 5 wherein the bus driver outputs pulses having amplitudes of a chosen multiple of the amplitude of the pulses across the sensor in the current-to-voltage converter and wherein the voltage and current related to the sensor are unaffected by the voltage and currents appearing on the bus and wherein the bus driver source pulses onto the bus in a non-feedback manner.

7. Apparatus as defined in claim 6 wherein the chosen multiple of the amplitude of the driver output pulses is about four times that of the amplitude of the output pulses from the current-to-voltage converter during transmissions.

8. Apparatus as defined in claim 7 wherein the output circuit of the bus driver and the input circuit of the receiver circuit of each node connect to a common point of the bus in a manner permitting effecting arbitration between nodes when more than one node attempts to gain control over transmitting messages over the bus.

9. A node transceiver of a multi-node network having a communications bus interconnecting the nodes permitting asynchronous communication between nodes providing to the network information from an input device such as sensors and switches, each node connected to the bus having (1) a regulated power source connected to a fixed voltage to provide regulated logic voltages referenced with respect to a signal ground return, (2) a microcontroller (MCU) connected between the input devices associated with the node, a symbol encoder decoder (SED) and the regulated power source, for receiving signals from the input device representing magnitudes of a measurand, formatting the received signals into digital messages, polling input and output ports connected to the SED, and initiating transmissions over the bus by controlling the operations of SED, and (3) the SED interconnected between the MCU and the transceiver for translating the digital messages from the MCU into variable pulse width modulated (VPWM) square-wave signals sent to other transceivers connected to the bus and for converting the square-wave digital signals received from other transceivers into digital messages used by the MCU for updating or controlling other peripherals associated with the network, said transceiver comprising:

a. integrating means for converting the VPWM square-wave signals received from SED into a decreased amplitude, 180 degrees out-of-phase trapezoid waveform signals referenced with respect to bounding fixed voltage levels, the trapezoid waveform signals having consistent pulse widths at chosen trigger points which continues to define the symbol information placed in the original square-wave pulses;

b. waveshaper means coupled to the integrator means for intercepting and then reshaping the corners at the extremities of each edge of the pulses of the trapezoid waveform signals, and providing gain and controlled gain reduction parameters, yet retaining the consistent pulse width at the trigger points of the pulses;

c. voltage-to-current converter means for using the reshaped trapezoidal waveform signals to provide varying control current source signals with respect to signal ground return in response to changes in amplitude and duration of the reshaped trapezoid waveform pulse signals;

d. a ground translation means connected in an output loop of the voltage-to-current converter for transferring the reference of the varying control current source signals formed in the voltage-to-current converter from the signal ground return to the independent bus ground return, and for using the converted current to establish a varying reference voltage levels used for controlling sourcing current onto the bus during node transmissions, the varying reference voltage levels being unaffected by changes in current and voltages on the bus.

e. bus driver means responsive to the varying reference voltage levels for proving amplified reshaped pulse signals which route to the bus providing symbol messages on the bus that minimizes electromagnetic interference in the vehicle if the bus voltage levels remain below the reference voltage levels of the translation circuit, the bus driver

10. Apparatus as defined in claim 9 wherein the receiver circuit and the bus driver means of each node connect to a common point of the bus in a manner that permit achieving arbitration between nodes attempting to gain control over the bus in order to transmit, the arbitration taking place substantially at the same time when the competing nodes are attempting to transmit messages.

11. Apparatus as defined in claim 10 wherein the voltages and current levels appearing on the bus may be affected by a mismatch of reference voltages in the various nodes connected to the bus and a timing mismatch of the current sourced on the bus by the bus driver circuits and received by the receivers and a loss of arbitration of competing nodes.

12. Apparatus as defined in claim 11 wherein the receiver circuit in each node contains ground translation circuits for changing the references of the received signals from the bus ground return to the signal ground return.