Microprocessor FSK data communications module

• US 4,689,801 A
• Filed: 10/11/1983
• Issued: 08/25/1987
• Est. Priority Date: 10/11/1983
• Status: Expired due to Term

• Current Assignee: American Standard Companies Incorporated (Ideal Standard International Topco SCA)
• Original Assignee: American Standard Companies Incorporated (Ideal Standard International Topco SCA)
• Inventors: Wilson, Patrick J., Nurczyk, Mark E., Wood, Tony J.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Rokoff, Kenneth I.
• Application Number:
  US06/540,220
• Time in Patent Office: 1,414 Days
• Field of Search: 375/62, 375/45, 375/9, 375/8, 375/7, 455/84
• US Class Current: 375/223
• CPC Class Codes: H04L 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence

Abstract

A microprocessor-based frequency shift keying (FSK) data communications module. The microprocessor selectively modulates and demodulates data directly in terms of a square wave pulse train in which a first frequency is used to convey a binary "1" and a second frequency to convey a binary "0". An input and an output port on the microprocessor are selectively coupled to a transmission line through a transformer, by means of electronic switches. Also included are a bandpass filter for shaping the square waves into sine waves and for filtering noise, and means including a notch filter for generating a carrier detect signal input to the microprocessor, when incoming data is detected on the transmission line. Many of the components in the module are used for both transmitting and receiving data.

Claims

1. A frequency shift keyed (FSK) data communications module adapted for a connection to a transmission line and selectively operable in both a receive and transmit mode said module comprising

a. a microprocessor having a plurality of electrical connection pins for input and output, said microprocessor being used for modulating and demodulating square wave signals carrying data that are respectively transmitted and received in a frequency shift keying format on the transmission line, said microprocessor including a single pin input port and a single pin output port for receiving and sourcing the square wave signals;

b. means for selectively coupling one of the input and output ports to the transmission line, which are operative to modify the FSK signal received thereon in the receive mode and to modify the square wave signals produced by the microprocessor in the transmit mode; and

c. means for switching the coupling means between the input port and the output port whereby the coupling means can function in both the receive and transmit modes.

2. The FSK data communications module of claim 1 further comprising means for detecting the presence of a carrier on the transmission line, and generating a carrier detect signal that is input to the microprocessor, whereby upon receipt of the carrier detect signal, the module begins to operate in the receive mode so that the microprocessor can demodulate the incoming signal.

3. The FSK data communications sxdule of claim 1 wherein the coupling means comprise a transformer.

4. The FSK data communications module of claim 1 further comprising a zero crossing detector disposed between the switching means and the input port, said detector being operative to provide the square wave signal in phase with a receive FSK data signal to the input port of the microprocessor.

5. The FSK data communications module of claim 1 wherein the switch means comprise a first and a second electronic switch, actuated in response to a switching signal output from the microprocessor.

6. The FSK data communications module of claim 5 further comprising a bandpass filter disposed between the first and second switches and operative to filter out unwanted signals when the module is receiving data, and to wave shape an output signal when the module is transmitting data.

7. The FSK data communications module of claim 6 further comprising a summing amplifier electrically connected to the bandpass filter and the switching means, and in combination with the bandpass filter comprising a notch filter.

8. A FSK data communications module for receiving and transmitting FSK data on a transmission line, said module comprising

a. a microprocessor including memory means for storing a program by which the microprocessor is caused to modulate a square wave output signal in a FSK data transmit mode and to demodulate a square wave input signal in a FSK data receive mode, the output signal being presented at a data output port and the input signal accepted at a data input port;

said microprocessor also being operative to output a mode select signal and to accept and respond to a carrier detect signal indicative of an incoming signal present on the transmission line;

b. a transformer used to couple the module to the transmission line;

c. means electrically connected both to the transformer and to the microprocessor, for generating the carrier detect signal in response to an incoming FSK signal present on the transmission line;

d. a bandpass filter; and

e. a switching network connected between the transformer, the bandpass filter, the input port, and the output port, said switching network being responsive to the mode select signal to connect the output port to the transformer through the bandpass filter in the transmit mode, and to connect the input port to the transformer through the bandpass filter in the receive mode.

9. The FSK data communications module of claim 8 further comprising a notch filter electrically connected between the transformer and the means for generating a carrier detect signal.

10. The FSK data communications module of claim 9 wherein the notch filter comprises the bandpass filter and an amplifier.

11. The FSK data communications module of claim 8 further comprising a zero crossing detector connected to the input port of the microprocessor and through the switching means, to the bandpass filter when the module is in the receive mode, said zero crossing detector being operative to provide a square wave signal to the input port, that is in phase with a sine wave signal that passes through the bandpass filter from the transmission line.

12. A method of communicating digital information from one microprocessor to another over a transmission line using an FSK format, comprising the steps of

a. generating square waves of predetermined frequencies in one of the microprocessor, as FSK pulses output at a port of said one micorprocessor, according to a stored program;

b. filtering the output pulse square waves to produce sine waves of equivalent frequencies using a bandpass filter;

c. electrically coupling the filtered output pulses to the transmission lines;

d. detecting the presence of the sine wave FSK pulses on the transmission line by comparing the amplitude of the signals in the expected frequency band with the amplitude of the signal outside that band and generating a carrier detect signal input to the other microprocessor if the inband amplitude is greater, causing the other microprocessor to operate in a receive mode and to process the received FSK signal with the same bandpass filter used in a transmit mode;

e. changing the sine wave FSK pulses to a square wave pulse signal of equal frequencies and coupling the square wave pulse signal to an input port on the other microprocessor; and

f. demodulating the square wave FSK pulses received at the input port of said other microprocessor to interpret the digital information according to a stored program.

13. The method of claim 12 wherein the step of converting the sine wave FSK pulses to square wave FSK pulses of equivalent frequencies includes the step of using a zero crossing detector.

14. The method of claim 13 further including the step of filtering the sine wave FSK pulses input to the zero crossing detector using the bandpass filter.

15. A frequency shift keyed (FSK) data communications module, adapted for connection to a transmission line, said module comprising

a. a microprocessor that modulates and demodulates data respectively transmitted and received in a frequency shift keying format on the transmission line, said microprocessor having a plurality of electrical connection pins for input and output including a single pin input port and a single pin output port for receiving and transmitting the data;

b. a bandpass filter having an input and an output;

c. a zero crossing detector having an input and an output, with its output connected to the input port of the microprocessor;

d. a transformer having a first winding and a second winding with the first winding connected to the transmission line; and

e. switch means controlled by the microprocessor for selectively coupling the input of the bandpass filter to the microprocessor output port and output of the bandpass filter to the second winding of the transformer in the transmit mode, and for selectively coupling the input of the bandpass filter to the second winding of the transformer and the output of the bandpass filter to the input of the zero crossing detector in a receive mode, whereby the bandpass filter is used in both the receive and transmit modes.

16. The FSK data communications module of claim 15 further comprising means electrically connected to both the second winding of the transformer and to the microprocessor for generating a carrier detect signal in response to an incoming FSK signal present on the transmission line, said carrier detect signal being input to the microprocessor and operative to cause the microprocessor to select the receive mode.

17. The FSK data communications module of claim 16 further comprising a notch filter electrically connected between the second winding of the transformer and the means for generating a carrier detect signal.

18. The FSK data communications module of claim 17 wherein the notch filter comprises the bandpass filter and an amplifier.

19. The FSK data communications modules of claim 15 wherein the bandpass filter is operative to filter out unwanted signals present on the transmission line when connected in the receive mode, and to wave shape an output signal when connected in the transmit mode.

20. The FSK data communications module of claim 15 wherein the switch means comprise a first and a second electronic switch.