System and method for serial communication between a central unit and a plurality of remote units

• US 6,108,614 A
• Filed: 05/14/1996
• Issued: 08/22/2000
• Est. Priority Date: 01/26/1995
• Status: Expired due to Term

• Current Assignee: Diablo Research Corporation
• Original Assignee: Diablo Research Corporation
• Inventors: Lincoln, Larry A., Fritz, Kent A., Russ, Jr., Robert M., Ruffo, Denis C.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US08/711,998
• Time in Patent Office: 1,561 Days
• Field of Search: 340/825.54, 340/825.12-825.15, 370/85.11, 370/85.8-85.1, 370/438, 370/447, 370/452, 702/183, 714/4, 701/20, 701/275, 701/277, 709/400, 709/825.05-825.08
• US Class Current: 702/183
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/56 Remote control
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values

Abstract

A user-responsive system has a controller and a plurality of remotes. Each remote typically has a corresponding sensor and/or actuator. Applications for this system include, but are not limited to heating, ventilating, and air conditioning systems, lighting systems, security systems, energy management systems, home automation systems, and home entertainment systems.

Claims

1. A system for transmitting data between a central unit and one or more remote units, the system comprising:

one common data line operatively coupling the central unit to each of the one or more remote units;

one common attention line operatively coupling the central unit to each of the one or more remote units;

means within the central unit for placing the data on the one common data line, the data including a message having an address indicative of at least one of the one or more remote units intended to receive the data;

means within the central unit for framing the address with an attention signal placed on the one common attention line, the attention signal having a leading edge and a trailing edge;

means within each one of the one or more remote units for storing a unique identification code;

means within each one of the one or more remote units for comparing the address from the one common data line with the unique identification code within each one of the one or more remote units only when the address is framed by the attention signal; and

means within each one of the one or more remote units for monitoring the one common data line for a remaining portion of the message when the address corresponds to the unique identification code within one of the one or more remote units.

2. The system according to claim 1 wherein the comparing means of at least one of the one or more remote units is configured to detect the leading edge of the attention signal on the one common attention line as an indication that the address is about to be placed by the central unit on the one common data line.

3. The system according to claim 1 wherein the address has a start bit and the comparing means of at least one of the one or more remote units is configured to detect the start bit and check the one common attention line for the attention signal as an indication that the address is being placed by the central unit on the one common data line.

4. The system according to claim 1 wherein the data include a plurality of bytes and the comparing means of at least one of the one or more remote units is configured to detect one of the plurality of bytes and check the one common attention line for the attention signal as an indication that one of the plurality of bytes currently on the one common data line is the address.

5. The system according to claim 1 wherein at least one of the one or more remote units has means for receiving and transmitting data on the one common data line and the comparing means of the at least one of the one or more remote units is configured to detect the trailing edge of the attention signal on the one common attention line as an indication that the address is contained in the receiving and transmitting data means.

6. The system according to claim 1 wherein the comparing means of a first one of the one or more remote units is configured to detect the leading edge of the attention signal on the one common attention line as an indication that the address is about to be placed by the central unit on the one common data line.

7. The system according to claim 6 wherein the address has a start bit and the comparing means of a second one of the one or more remote units is configured to detect the start bit and check the one common attention line for the attention signal as an indication that the data currently on the one common data line is the address.

8. The system according to claim 7 wherein the data include a plurality of bytes and the comparing means of a third one of the one or more remote units is configured to detect one of the plurality of bytes and check the one common attention line for the attention signal as an indication that the one of the plurality of bytes currently on the one common data line is the address.

9. The system according to claim 8 wherein a fourth one of the plurality of remote units has means for receiving and transmitting data on the one common data line and the comparing means of the fourth one of the one or more remote units is configured to detect the trailing edge of the attention signal on the one common attention line as an indication that the address is contained in the receiving and transmitting data means.

10. A method for serial communication between a central unit and one or more remote units each having a unique identification code, the method comprising the steps of:

coupling the central unit to each of the one or more remote units with one common data line and one common attention line;

transmitting information from the central unit on the one common data line having an address and a remaining message;

framing the address with an attention signal on the one common attention line generated by the central unit;

comparing the address in each of the one or more remote units only if the attention signal is framing the address; and

processing the remaining message in a desired remote unit of the one or more remote units in which the unique identification code matched the transmitted address.

11. The method according to claim 10 wherein the step of transmitting information on the one common data line comprises the sub-steps of:

transmitting first a start bit;

transmitting second a byte of the information; and

then

transmitting a plurality of stop bits while the central unit prepares a next segment of the information to be transmitted.

12. The method according to claim 11 wherein the plurality of stop bits is 9 and 80 bits whereby ensuring under half utilization of the one common data line thus allowing the one or more remote units an opportunity to processes the bits during the one or more stop bits.

13. The method according to claim 11 wherein the step of processing the remaining message further includes the sub-steps of:

locating the plurality of stop bits in an expected location; and

accepting the transmitted byte of information only if the plurality of stop bits are located in the expected location.

14. The method according to claim 13 further comprising the step of an interrupting remote unit from one of the one or more remote units obtaining immediate attention of the central unit including the sub-step of:

causing the desired remote unit to fail to locate the plurality of stop bits in the expected location by the interrupting remote unit transmitting an interrupt signal of opposite polarity to the plurality of stop bits for sufficient time to ensure overlap with the expected location of the plurality of stop bits.

15. The method according to claim 14 further comprising the steps of stopping the interrupt signal and looking on the one common data line for the interrupt signal to determine whether another one of the one or more remote units is also attempting to interrupt a current message.

16. The method according to claim 10 wherein the remaining message from the central unit on the one common data line includes a command for the desired remote unit to perform some function, the method further including the step of waiting to contact the desired remote unit during its performance of the command.

17. The method according to claim 16 further including the step of the desired remote unit ignoring the data on the one common data line during its performance of the command.

18. The method according to claim 10 wherein the information includes the address having one-byte length and a remaining message each portion of which having a one-byte length, said remaining message including at least a one-byte command field, a one-byte length field, and a one-byte error-checking field, the method further comprises the steps of:

splitting in the central unit each byte into nibbles in order of transmission on the one common data line;

calculating in the central unit a Fletcher checksum from the nibbles, least significant and then most significant nibble in order of transmission on the one common data line;

complementing in the central unit the Fletcher checksum, wherein the complemented Fletcher checksum comprises the one-byte error-checking field;

splitting in the desired remote unit each byte into nibbles in order of receipt on the one common data line;

calculating in the desired remote unit the Fletcher checksum from the nibbles, least significant and then most significant nibble in order of transmission on the one common data line including the one-byte error-checking field;

accepting the information in the desired remote unit only if the Fletcher checksum calculated therein is zero.

19. The method according to claim 10 further comprising the steps of:

transmitting information from the desired remote unit only if the Fletcher checksum calculated therein is zero, the information including at least a one-byte command field, a one-byte length field, and a one-byte error-checking field;

splitting in the desired remote unit each byte as well as the unique identification code into nibbles the unique identification code first and then each byte in order of transmission onto the one common data line;

calculating in the desired remote unit a Fletcher checksum from the nibbles least significant nibble and then most significant nibble in order of transmission on the one common data line;

complementing in the desired remote unit the Fletcher checksum, wherein the complemented Fletcher checksum comprises the one-byte error-checking field;

splitting in the central unit the address as well as each byte into nibbles the address first and then each byte in order of reception on the one common data line;

calculating in the central unit the Fletcher checksum from the nibbles least significant and then most significant nibble in order of transmission on the one common data line; and

accepting the information in the central unit only if the modified Fletcher checksum calculated therein is zero.

20. A method for error-checking in a system having a central unit and one or more remote units, the central unit and one or more remote units being connected by one common data line, the method comprising the steps of:

transmitting information from the central unit on the one common data line, the information including at least a one-byte address, a one-byte command field, a one-byte length field, and a one-byte error-checking field;

splitting in the central unit each byte into nibbles in order of transmission on the one common data line;

calculating in the central unit a Fletcher checksum from the nibbles, least significant and then most significant nibble in order of transmission on the one common data line;

complementing in the central unit the Fletcher checksum, wherein the complemented Fletcher checksum comprises the one-byte error-checking field;

splitting, in a desired remote unit of the one or more remote units in which the unique identification code matched, each byte into nibbles in order of receipt on the one common data line;

calculating in the desired remote unit the Fletcher checksum from the nibbles, least significant and then most significant nibble in order of transmission on the one common data line including the one-byte error-checking field;

responding to the command in the desired remote unit only if the Fletcher checksum calculated therein is zero;

transmitting return information from the desired remote unit only if the Fletcher checksum calculated therein is zero, the return information including at least a one-byte command field, a one-byte length field, and a one-byte error-checking field;

splitting in the desired remote unit the unique identification code as well as each byte into nibbles the unique identification code first and then each byte in order of transmission onto the one common data line;

calculating in the desired remote unit a Fletcher checksum from the nibbles least significant nibble and then most significant nibble;

complementing in the desired remote unit the Fletcher checksum, wherein the complemented Fletcher checksum comprises the one-byte error-checking field;

receiving in the central unit the return information from the desired remote unit on the one common data line;

splitting in the central unit the address as well as each byte of the return information into nibbles the address first and then each byte in order of reception on the one common data line;

calculating in the central unit the Fletcher checksum from the nibbles least significant nibble and then most significant nibble in order; and

accepting the information in the central unit only if the modified Fletcher checksum calculated therein is zero.

21. A remote unit for communicating with a central unit over one data line and one attention line each line being operatively coupled between the remote and central units, the one data line transmitting information including at least an address and a command, the attention line transmitting an attention signal which frames the address on the one data line, the remote unit comprising:

means for storing a unique identification code;

means for comparing the address from the one data line with the unique identification code only when the address is framed by the attention signal; and

means for responding on the one data line to the command with return information if the address corresponds to the unique identification code,

the responding means including means for calculating an error-check field based on the return information and unique identification code even though the unique identification code is not transmitted back to the central unit.