Abstract:
At least one exemplary embodiment of the present invention includes a device that comprises a microprocessor, a multiplexing analog-to-digital converter integral to said microprocessor, and a reference voltage source connected to said multiplexing analog-to-digital converter. At least one exemplary embodiment of the present invention includes a method that comprises obtaining a signal at a multiplexing analog-to-digital converter integral to a microprocessor; and comparing a digital value of the signal to a reference digital value. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. This abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to, and incorporates by reference herein in its entirety, the pending provisional application Ser. No. 60/368,419, (Attorney Docket No. 2002P05386), filed Mar. 28, 2002. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0002]    The invention and its wide variety of potential embodiments will be readily understood via the following detailed description of certain exemplary embodiments, with reference to the accompanying drawings in which:  
           [0003]    [0003]FIG. 1 is an electrical diagram of an exemplary embodiment of a system  1000  of the present invention; and  
           [0004]    [0004]FIG. 2 is a flow diagram of an exemplary embodiment of a method 2000. 
       
    
    
     DETAILED DESCRIPTION  
       [0005]    At least one exemplary embodiment of the present invention includes a device that comprises a microprocessor, a multiplexing analog-to-digital converter integral to said microprocessor, and a reference voltage source connected to said multiplexing analog-to-digital converter.  
         [0006]    At least one exemplary embodiment of the present invention includes a method that comprises obtaining a signal at a multiplexing analog-to-digital converter integral to a microprocessor; and comparing a digital value of the signal to a reference digital value.  
         [0007]    [0007]FIG. 1 is an electrical diagram of an exemplary embodiment of a system  1000  of the present invention. System  1000  can include a microprocessor  1060  having an integral a multiplexing analog-to-digital converter portion  1061  to which a reference voltage source  1010  is connected to provide a reference input  1062 . System  1000  can be integral to a programmable logic controller.  
         [0008]    In one exemplary embodiment, microprocessor  1060  can be a general-purpose microprocessor, such a Pentium series microprocessor manufactured by the Intel Corporation of Santa Clara, Calif. Attached to microprocessor  1060  can be a memory  1080 , which can store instructions  1085  adapted to be executed by microprocessor  1060  according to one or more activities of method  2000  (described below). Memory  1080  can be any device capable of storing analog or digital information, such as a hard disk, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, memory stick, a compact disk, a magnetic tape, a floppy disk, etc., and any combination thereof. Instructions  1085  also can be embodied in software, which can take any of numerous forms that are well known in the art.  
         [0009]    In another exemplary embodiment, microprocessor  1060  can be provided as an application-specific integrated circuit (ASIC), and can also include an integral memory portion. Thus, microprocessor  1060  can be designed to implement in its hardware and/or firmware at least a part of a method in accordance with an embodiment of the present invention.  
         [0010]    A plurality of sensors,  1020 ,  1030 , . . .  1040  can be connected to multiplexing analog-to-digital converter portion  1061 . From first sensor  1020  can promulgate a first sensor signal defined by a current I 1 , from second sensor  1030  can promulgate a second sensor signal defined by a current I 2 , . . . and from Nth sensor  1040  can promulgate an Nth sensor signal defined by a current I N . Each of currents I 1 , I 2   2 , . . . I N  can flow through a high precision input resistor  1050 , resulting in voltages V 1 , V 2 , . . . V N  that characterize input signals  1064 ,  1066 , . . .  1068  at multiplexing analog-to-digital converter portion  1061 . Note that any of input signals at  1020 ,  1030  . . .  1040  can be transmitted by direct wire or given the appropriate conversion and communication equipment, be transmitted via any form of network, including a public switched telephone network (PSTN), a wireless network, a cellular network, a local area network, the Internet, etc.  
         [0011]    Multiplexing analog-to-digital converter portion  1061  can receive and multiplex any number of analog input signals  1064 ,  1066 , . . .  1068 , and can convert each from an analog to a digital signal, such as by converting an analog voltage value to a digital voltage value. Microprocessor  1060  can compare a reference value, such as a reference voltage value, stored in memory  1080  (which can be integral to microprocessor  1060 ) to each digital value and determine a status of each sensor  1020 ,  1030  . . .  1040 .  
         [0012]    Microprocessor  1060  can then output a status signal  1069  to a second microprocessor  1070 , such as the main processor of a programmable logic controller. Upon start-up, second microprocessor  1070  can provide reference value(s) to microprocessor  1060 , which can store the reference value(s) in memory  1080 .  
         [0013]    [0013]FIG. 2 is a flowchart of an exemplary embodiment of a method  2000  of the present invention. At activity  2010 , for a given sensor type, a digital reference value is determined.  
         [0014]    As an example, Table 1 provides current ranges that an illustrative sensor will produce under various conditions, such as a shorted circuit or sensor, a valid logical 1, a transition between logic states, a valid logical 0, and an open circuit. Table 1 also lists the resulting input voltages to the analog-to-digital converter if the sensor is connected to, for example, a 237 ohm precision resistor. Table 1 further lists the ratio of the resulting input voltages to a reference voltage, which in this example is 2.5 volts. Table 1 also lists a reference value expressed, for the purposes of this example, as an 8 bit (modulo 256) digital value.  
                               TABLE 1                           Current   Input Voltage   Ratio to reference   Reference       Sensor Status   (milliamps)   (volts)   voltage (%)   value                   Shorted   &gt;7.0    &gt;1.659   &gt;66.4   &gt;169       Logical 1   2.1-7.0   0.498-1.659   19.9-66.4    51-169       Transition between   1.2-2.1   0.284-0.498   11.4-19.9   29-51       Logical states       Logical 0   0.35-1.2    0.083-0.284   0.033-11.4     8-29       Open (e.g., broken wire)   &lt;0.35   &lt;0.083    &lt;0.033   &lt;8                   
 
         [0015]    In alternative embodiments, nearly any other resistor value could be used, but the value chosen is typically related to the reference voltage and input current. If a lower reference voltage is chosen, a smaller resistor value can be used to achieve the same range of reference values. For example, with a reference voltage of 2.5V, and a maximum input current of 10 mA, a value of 250 Ohms could be used to get a maximum input count at the maximum input current. A smaller resistor value can be chosen to allow for tolerances in the resistor, in the voltage supply that drives the sensors, and/or variations in the sensor.  
         [0016]    As another example, other common reference voltages include 2.0V, 1.5V, and 1.25V. Other lower voltage values can be expected in the future as technology pushes for lower and lower operating voltages for both analog and digital circuitry. As a further example of possible alternative embodiments, other possible resolutions include 4 bit, 6 bit, 8 bit, 10 bit, 12, bit, 14 bit, 16 bit, and higher.  
         [0017]    At activity  2020 , a memory is populated with the digital reference values, so that the digital reference values can be looked-up when needed. At activity  2030 , the multiplexing analog-to-digital converter portion of the microprocessor receives a reference signal having a reference voltage level. At activity  2040 , the multiplexing analog-to-digital converter portion of the microprocessor also receives a sensor signal having a sensor voltage. The sensor voltage is the result of the sensor&#39;s output and the resistance value of the precision resistor.  
         [0018]    At activity  2050 , the sensor voltage level is normalized to the reference voltage level by dividing the sensor voltage level by the reference voltage level, to arrive at a dividend. At activity  2060 , the dividend is digitized by multiplying it by the number of counts in the analog-to-digital converter. For example, if the analog-to-digital converter can output a 10-bit value, it can output a value between 0 and 1023 (=2 10 −1). Thus, in this case, the dividend would be multiplied by 1023, the resulting product possibly rounded to the nearest integer, and the integer portion of the resulting product would represent the digital value of the normalized sensor voltage. Note that activities  2050  and  2060  can occur in the opposite order, such that the sensor voltage level is digitized prior to being normalized. In fact, any of activities  2010  to  2090  can occur in any appropriate order.  
         [0019]    At activity  2070 , the microprocessor can compare the digital normalized value to the digital reference values, such as those in Table 1. At activity  2080 , the microprocessor can determine the status of the sensor. At activity  2090 , the microprocessor can transmit the sensor status, such as to the second microprocessor, which can be part of a programmable logic controller.  
         [0020]    Referring to the example of Table 1, if a sensor outputs 1.0 milliamp, then 0.237 volts (237 ohms×0.001 amps) is input to the multiplexing analog-to-digital converter portion of the microprocessor. That input voltage represents 9.48% ((0.237÷2.5)×100%) of the reference voltage level. Because the maximum digital value of the analog-to-digital converter is 255, the analog-to-digital converter will output a count of 24 (0.0948*255, modulo 256). When the microprocessor compares the converter&#39;s digital output to the digital reference values stored in memory (i.e., those shown in Table 1), the microprocessor determines that a logical 0 was provided by the sensor, and provides an output signal consistent with this determination. A programmable logic controller can react as programmed to the fact that a logical 0 was provided by the sensor.  
         [0021]    Although the invention has been described with reference to specific embodiments thereof, it will be understood that numerous variations, modifications and additional embodiments are possible, and accordingly, all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the invention. Also, references specifically identified and discussed herein are incorporated by reference as if fully set forth herein. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive.