Patent Application
20070085696
The present invention relates generally to the field of controlling a receiver by a transmitter over a wireless communications channel, and more particularly to generating an identification for matching the transmitter with the receiver.
When many RF devices utilize the same frequency spectrum in close proximity to each other, a receiver may be controlled by the wrong transmitter. The traditional method to avoid the mismatching is to use dipswitch settings at both transmitter and receiver for pairing the transmitter and the receiver. The user typically configures the dipswitch settings of the transmitter to match the dipswitch settings of the paired receiver.
However, the approach is not flexible and is demanding on the user. Often, the user will select only the default setting and therefore incorrectly configure the system so that transmitters are incorrectly paired with receivers.
Consequently, there is a need to support transmitter-receiver pairing that is reliable and that facilitates system configuration by the user.
The present invention provides methods and apparatuses that support a flexible approach to pairing a transmitter and a receiver that use the same power line and power module while facilitating system configuration. The transmitter associates an identification number with a command message so that a receiver can ascertain whether a command message is intended for the receiver. The transmitter communicates with the receiver over a wireless communications channel.
With one aspect of the invention, the time from the power up of the transmitter-receiver pair to the first zero crossing of the AC signal that powers an associated AC-DC converter is approximately random. An associated identification number is used as a matching seed for both transmitter and receiver.
With another aspect of the invention, the transmitter generates an identification number by incrementing a counter each counting time interval between power up and the occurrence of a first zero crossing of the AC signal. The occurrence of the zero crossing is detected by a zero crossing detector.
With another aspect of the invention, the transmitter sends the generated identification number to the paired receiver after power up but before a predetermined time interval.
The receiver stores the generated identification number and compares the stored identification number with a received identification number that is received in a subsequent command message. If the stored identification number matches the received identification number, the receiver processes the command message and executes the associated action. Otherwise, the receiver ignores the received command message.
The foregoing summary of the invention, as well as the following detailed description of exemplary embodiments of the invention, is better understood when read in conjunction with the accompanying drawings, which are included by way of example, and not by way of limitation with regard to the claimed invention.
Each transmitter of the pair communicates with the corresponding receiver over a wireless communication channel in order to instruct the receiver to take an appropriate action (e.g., activating a heating system). In the configuration 100, transmitter 101 communicates with receiver 103 over wireless channel 151, and transmitter 105 communicates with receiver 107 over wireless channel 153. However, transmitter-receiver pairs may be located in close proximity to each other so that the receiver of one pair may undesirably receive a command signal from the transmitter of the other pair if the pairs utilize the same electromagnetic spectrum. In configuration 100, receiver 107 may undesirably receive a command signal from transmitter 101 over spurious wireless channel 155, and receiver 103 may undesirably receive a command signal from transmitter 105 over spurious wireless channel 157.
Each transmitter-receiver pair is associated with a corresponding identification number to distinguish one pair from another. For example, a first identification number (e.g., ‘099’) may be associated with the first pair (transmitter 101 and receiver 103), and a second identification number (e.g., “117’) may be associated with the second pair (transmitter 105 and receiver 107). When transmitter 101 sends a command message to receiver 103, transmitter 101 includes the first identification number in the command message. Receiver 103 stores the associated identification number and accepts the command message only if received identification number matches the stored identification number. Otherwise, receiver 103 ignores a received command message. Consequently, undesired communication over spurious wireless channels 155 and 157 are avoided.
In an embodiment of the invention, an identification number (which approximates a random number) is determined by calculating the time interval between power up and first zero crossing detected by the transmitter of an AC signal that provides electrical power to the transmitter-receiver pair. In configuration 100, as shown in
Microprocessor unit 201, as shown with the embodiment of
Counting module 203 may count of a time duration that spans more than one zero crossing so that the range of the generated identification number may be increased. If counting module increments a counter over the first two zero crossings, the counter has a range of 1/(2*Line_Frequency*Counter_Interval). (For example, zero crossing detector 215 does not distinguish between the positive and negative portions of a cycle.) In the previous example, the corresponding range of the generated identification number is 0 to 256, which spans one octet of memory. The above approach may be generalized to span N zero crossings so that the range of the generated identification number is expanded by a factor of N. In an embodiment of the invention, MCU 201 may utilize a value associated with the first zero crossing to determine the number of subsequent zero crossings during which counting module 203 counts to generate an identification number.
While zero crossing detector 215 determines when the AC signal crosses a voltage value of zero, other embodiments of the invention may utilize detectors that detect when the AC signal provided by AC power line 209 crosses a reference other than zero (e.g., +50 volts).
The embodiment of the invention, as shown in
In step 307, the counter is incremented by one time unit whenever an timer interrupt occurs. (The incrementing of counting module 203 is performed by Timer INT Subroutine 450 as will be discussed.) Each time unit corresponds to a timing incremental value (e.g., 64 μsec.) If the zero crossing flag is ‘0’, as initialized in step 303, counting module 203 is subsequently incremented with subsequent timer interrupts. However, if the zero crossing flag is ‘1’ (which corresponds to an zero crossing external interrupt and the execution of Zero Crossing INT Subroutine 400 as will be discussed), the generated identification number (equal to the counter value of counting module 203) is sent by transmitter 200 in step 309 to the paired receiver multiple times to insure that the paired receiver receives the generated identification number.
Step 311 determines whether a condition or a set of conditions, which corresponds to a particular action to be taken at the paired receiver, is satisfied. If so, transmitter 200 sends a command message to the paired receiver with the associated command code and the generated identification number in step 313.
In step 513, the paired receiver determines whether a command message has been received. If so, the paired receiver in step 515 determines whether the received identification number matches the stored identification number. If the received identification number matches the stored identification number, the corresponding command is executed by the paired receiver in step 517. If the received identification number does not match the stored identification number, the paired receiver ignores the command message and step 513 is repeated, where the paired receiver waits to receive the subsequent command message.
In an embodiment of the invention, transmitter 200 sends periodic messages (“heartbeat” messages) to the paired receiver even if no corresponding action is to be taken by the paired receiver. If no action is to be taken, the action corresponds to a “NOP” (no operation). However, periodic messages insure that the communication path between transmitter 200 and the paired receiver is reliable. If paired receiver does not receive periodic messages, the paired receiver may activate a communications warning indicator to indicate faulty communications between transmitter 200 and the paired receiver.
As can be appreciated by one skilled in the art, a computer system with an associated computer-readable medium containing instructions for controlling the computer system can be utilized to implement the exemplary embodiments that are disclosed herein. The computer system may include at least one computer such as a microprocessor, digital signal processor, and associated peripheral electronic circuitry.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
