Abstract:
A color measurement instrument wherein the communication protocol used by the instrument is determined by the cable attached to the instrument. The instrument includes a handheld unit having a control system capable of communicating in at least two different protocols through a common connector. This control system connector includes a set of pin-outs corresponding to each of the available protocols. The instrument also includes a cable having a connector mated with the control system connector. The pin-out of the cable connector corresponds to only one of the sets of pin-outs of the control system connector, so that the cable provides a communication pathway corresponding to only one of the available protocols.

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Application No. 60/113,754, filed Dec. 23, 1998 and entitled USB COLOR MEASUREMENT DEVICE. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to color measurement instruments, and more particularly to color measurement instruments capable of communicating in multiple protocols. 
     2. Description of Art 
     Color measurement instruments are capable of reading a color for the subsequent conversion of the color to a mathematical representation. That representation can be processed using techniques known to those skilled in the art to perform color functions such as calibration. Color measurement instruments include, by way of illustration and not limitation, spectrophotometers, colorimeters, densitometers, and spectroradiometers. 
     One particularly useful color measurement instrument is a monitor colorimeter (also known as a colorimetric radiometer) manufactured and sold by X-Rite Incorporated (X-Rite) of Grandville, Mich. as Model No. DTP92Q. This colorimeter is a tethered desktop unit for monitor calibration, and it includes a handheld unit and a cord for connecting the unit to the serial port of a computer. The handheld unit can be positioned over a portion of a monitor screen to read the color displayed on that portion of the screen. The color information or representation is communicated to the computer through the cord. The communication protocol for the colorimeter is RS232. The color information received by the computer from the colorimeter can be processed using color management software such as that sold by X-Rite under the trademark COLOR SHOP or that sold by Apple Computer under the trademark COLORSYNC. 
     While the DTP92Q colorimeter has enjoyed widespread popularity, it is dependent on the RS232 protocol. Although RS232 has been the serial communication protocol standard for a considerable period, computer manufacturers and the computer industry are developing new and improved protocols. For example, the Universal Serial Bus Implementers Forum (USBIF) recently developed a new protocol known as Universal Serial Bus (USB); and Apple Computer is phasing out the inclusion of RS232 serial ports on new computers. A unit such as the DTP92Q, which is capable of communicating only in the RS232 protocol, is not compatible with the USB protocol. Additional future changes in communications protocols are anticipated. For example, one such protocol is known as Fire Wire. Accordingly, it is possible that a colorimeter redesigned for the USB protocol may itself be outdated shortly. 
     SUMMARY OF THE INVENTION 
     The aforementioned problems are overcome in the present invention wherein a color measurement instrument is capable of multiple communication protocols each associated with a unique interface cable. The implemented protocol is selected by connecting the appropriate cable to the handheld unit—either during manufacture or during subsequent service. 
     More specifically, the color measurement instrument includes on-board hardware, firmware and/or software capable of communicating in a variety of protocols through a common internal connector. Any one of a variety of cables may be connected to the connector. Each of the cables is uniquely associated with a particular communication protocol and includes a connector interfitting with the connector within the instrument. Appropriate connections are made between the cable connector pin-outs and the on-board connector pin-outs so that the instrument communicates though the cable in the selected protocol. 
     In the disclosed embodiment, the instrument is capable of communicating in both the RS232 protocol and the USB protocol. A first cable is unique to the RS232 protocol, and a second cable is unique to the USB protocol. Either cable may be connected to the instrument, and particularly to the internal connector. After a particular cable has been connected, the instrument communicates in the selected protocol through the cable. 
     As will be appreciated, the present invention is not restricted to the particular protocols disclosed. The invention is readily extendable to other exiting protocols and to future communication protocols. 
     The present invention provides improved flexibility for color measurement instruments. With the exception of the cable, the instrument is “generic” to all protocols. Only the cable varies by instrument to implement a desired protocol. The “generic” design of the instrument simplifies manufacture, testing, and calibration. During manufacture, the instrument can be tested and calibrated using any one of the available protocols. 
     These and other objects, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the color measurement instrument of the present invention in conjunction with a computer monitor; 
     FIG. 2 is a perspective view of the instrument of the present invention; 
     FIG. 3 is a detailed view showing the connection of the communication cable to the handheld unit; 
     FIG. 4 is a schematic diagram of the handheld unit; 
     FIG. 5 is a schematic diagram of the RS232 cable; 
     FIG. 6 is a schematic diagram of the USB cable; 
     FIGS. 7-8 are flow charts illustrating the operation of the prior art instrument in the RS232 protocol; 
     FIGS. 9-11 are flow charts illustrating the operation of the present instrument in multiple protocols. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A color measurement instrument constructed in accordance with a preferred embodiment of the invention is illustrated in FIGS. 1 and 2 and generally designated  10 . As disclosed, the instrument  10  is a monitor colorimeter (also known as a colorimetric radiometer). However, the invention is considered to encompass any color measurement instrument including, but not limited to, spectrophotometers, colorimeters, densitometers, and spectroradiometers. 
     The instrument  10  includes a handheld unit  12  and a cable or cord  14 . The handheld unit is capable of communicating in multiple communication protocols. Any particular cable  14  is unique to a particular communication protocol. The cable illustrated in FIGS. 1-3 is adapted for communication in the Universal Serial Bus (USB) protocol. 
     With the exception of the multiple communication protocol capability to be described, the handheld unit  12  is generally well known to those skilled in the art. For example, one similar unit has been sold by X-Rite as a monitor colorimeter under the model designation DTP92Q. Accordingly, this description will focus on the new invention related to the multiple communication protocol capability. 
     The hardware of the handheld unit  12  is schematically illustrated in FIG.  4 . The prior art components within that handheld unit include a microcontroller  20 , a program memory  22 , a data memory  24 , photodiodes  26 , an A/D (analog to digital) converter  28 , and a voltage regulator  30 . Accordingly, these components will be described only briefly. The microcontroller  20  provides overall control for the unit  12 . More specifically, the microcontroller  20  receives digital input from the photodiodes  26  through the A/D converter  28  and converts those signals to coordinates in a color space. The acquired data is stored in the data memory  24 . The firmware or software program control is stored in the program memory  22 . The voltage regulator  30  provides internal regulated power to the unit  12 . 
     The new components within the handheld unit  12  include the ten-pin connector  40 , the USB interface chip  42 , and the associated electrical connections. These components are commercially available, but are uniquely used within the present instrument as part of the present invention. 
     The USB interface chip  42  operates within the USB protocol. More specifically, the chip  42  defines four subsets of the USB protocol and is capable of communicating within any one of those subsets. The present invention utilizes only the “bulk transfer” subset, but other subsets could be used in its place. The interconnection/interface of the USB chip  42  with the microcontroller  20  is well known to those skilled in the art. Alternatively, the microprocessor  20  and the USB interface could be incorporated into a single chip, and such chips are commercially available. Other implementations will be recognized by those skilled in the art. 
     The connector  40  (FIGS. 3-4) is an in-line, ten-pin connector conventional in the art. Other connectors, both known and developed in the future, could also be readily used to implement the present invention. FIG. 4 illustrates the pin-outs of the ten-pin connector. Pin  1  is connected to the input voltage (+VIN). Pins  2 ,  8 , and  10  are commonly connected to ground (GND). Pin  3  is connected to the microcontroller  20  via the RS232 transfer data (TXD) line  31   a,  and pin  4  is connected to the microcontroller  20  via the RS232 receive data line (RXD)  31   b.  Pin  7  is connected to the USB chip  42  via the USB data high (USBD+) line  43   a,  and pin  9  is connected to the USB chip  42  via the USB data low (USBD−) line  43   b.  Pins  5  and  6  are “spares” that are not assigned. 
     The USB cable  14  (FIGS. 1-3 and  5 ) includes a USB connector  50 , a strain relief  52 , and a ten-pin connector  54  (see FIG.  3 ). The USB cable  14  includes at least four wires/connections to communicate in the USB protocol. The USB connector  50  is known to those skilled in the art and is suited for insertion into a USB socket S, for example in the front of monitor M as illustrated in FIG.  1 . The strain relief  52  is also well known to those skilled in the art and reduces strain on the cable  14  where it passes through and is connected to the unit  12 . See FIG.  3 . 
     The individual connections between the pins of the USB connector  50  and the ten-pin connector  54  on the opposite ends of the USB cable  14  are illustrated in FIG.  6 . Specifically, pins  1 - 4  of the USB connector  50  are connected to pins  1 ,  9 ,  7 , and  2 , respectively, of the ten-pin connector  54 . Accordingly, pin  1  of the ten-pin connector provides an input voltage; pin  2  provides a ground; pin  7  provides data high; and pin  9  provides data low. 
     As perhaps best illustrated in FIG. 3, the ten-pin connector  54  of the cable  14  can be physically connected to the ten-pin connector  40  of the unit  12 . When so connected, the pin-outs  1 - 10  of the connector  54  are connected to the associated pin-outs  1 - 10  of the connector  40 . When so connected, the voltage regulator is operatively connected to the input voltage (+VIN); the grounds (GND) are connected; and the data lines (USBD+ and USBD−) are connected through lines  43   a  and  b  to the USB interface chip  42 . The unit  12  therefore receives appropriate power and is grounded. Similarly, the microcontroller is capable of communicating in the USB protocol through the chip  42 . 
     The RS232 cable  14 ′ is illustrated in FIG.  5  and includes a power connector  50 ′, an RS232 connector  50 ″, and a ten-pin connector  54 ′. All three connectors are of a type known to those skilled in the art. Pins  1  and  2  of the power connector  50 ′ are electrically connected to pins  1  and  8  of the 10-pin connector  54 ′. Pins  2 ,  3 , and  5  of the RS 232 connector  50 ″ are electrically connected to pins  3 ,  4 , and  2  of the connector  54 ′. Accordingly, the input voltage (+VIN) is supplied to pin  1  of the connector  54 ′; ground (GND) is applied to pins  2  and  8 ; and data lines (TXD and RXD) are applied to pins  3  and  4 . 
     Alternatively, a single cable having both types of connectors—one for each protocol—connected thereto could be used. In such case, only one of the connectors would be connected to the instrument at any given time; and the necessary pin-outs for both protocols would be included in the single cable. 
     Assembly and Operation 
     All of the electrical components schematically illustrated in FIG. 4 are mounted within the handheld unit  12  and are connected to each other using techniques customary in the art. The ten-pin connector  40  is available within the unit  12  for connection to one of the cables  14  or  14 ′. 
     During manufacture, only one of the cables  14  or  14 ′ is connected to the ten-pin connector  40 . When the USB cable  14  is connected to the unit  12  (see FIGS.  4 - 5 ), the following pin-out connections are made: +VIN, GND, USBD+ and USBD−. When the RS232 cable  14 ′ is connected to the unit  12 , the following pin-out connections are made: +VIN, GND, TXD, and RXD. Accordingly, the appropriate and necessary pin-outs for the protocol uniquely associated with the corresponding cable  14  or  14 ′ are automatically connected as the ten-pin connectors are physically interconnected. After the selected cable has been connected to the connector  40 , the housing  13  is closed upon the strain relief  52  to capture the cable  14  or  14 ′ in fixed position with respect to the handheld unit  12 . 
     It presently is not expected that the ultimate consumer and/or user of the instrument  10  will change the cable connected to the handheld unit  12 . However, it is possible that trained service representatives could make a cable substitution to change the protocol in which the instrument communicates. To do so, the service personnel simply opens the housing  13 ; removes the existing cable  14  or  14 ′; installs the “other” cable  14  or  14 ′; and then closes the housing  13 . As will be appreciated from the following description of the firmware/software, no other changes are required to change the communication protocol of the instrument  10 . 
     It also is possible that the connector  40  could be located so as to be accessible from outside of the housing  13 . Such a construction would enable the ultimate consumer and/or user of the instrument  10  to readily and easily change the cable connected to the unit, and thereby change the communication protocol. In any of the implementations, it is possible that the instrument  10  will obtain all of its power requirements (in all modes of the instrument and in all protocols) through the connected cable. 
     The prior art software/firmware of the prior art unit is illustrated in FIGS. 7-8. 
     This software/firmware is carried into the present instrument  10 . The serial communication subroutine is illustrated in FIG.  7  and is executed  700  each time that the microcontroller  20  receives an interrupt signal indicating that an RS232 character must be processed. The received character is stored  701  in the next available character in the RCI (Remote Control Interface) buffer. If  702  the byte is a carriage return, then the executive functions subroutine (see FIG. 8) is notified  703  that a complete command string has been received. If  702  the byte is anything other than a carriage return, then the interrupt subroutine is exited  704 . As described and as is conventional, the RS232 serial communication occurs character by character. 
     The prior art software/firmware for the executive functions subroutine is illustrated in FIG.  8 . This software/firmware is carried forward into, and supplemented in, the present instrument  10 . All of the “other processing” of the unit  10  is illustrated as box  801 . When the serial communication subroutine (FIG. 7) indicates that a complete RCI string has been received  802 , control passes to box  803 . If  802  a complete RCI command string has not been received, control returns to the other processing  801 . In box  803 , the last two characters of the command string are separated from the remainder of the string. The last two characters specify the command to be performed, and the remainder of the string contains the parameters to the command. If the command characters are CF, a configuration function is executed  804 . If the command characters are BR, a band rate function is executed  805 . If the command characters are RM, a read monitor function is executed  806 . Similarly, other commands generically designated XX will cause other functions to be executed  807 . After the appropriate function has been executed, a response is sent  808  to the host computer indicating that the command has been processed and transferring any data that may have been requested by the host computer. 
     FIG. 9 illustrates the USB interrupt routine which is new to the instrument  10 . The routine starts  901  when an interrupt signal is received from the USB interface chip  42  (see FIG.  4 ). USB communication occurs in packets rather than character by character. An interrupt request is issued by the USB interface chip  42  only when a complete packet, comprising a complete command, has been received by the USB chip  42 . The executive functions routine is notified  902  that the USB chip requires service. Program flow then returns  903  to the other processing. 
     The executive functions subroutine of the present instrument  10  is illustrated in FIG.  10 . The portions of the executive functions subroutine outside of the dashed line  810  is identical to the executive functions subroutine of the prior art illustrated in FIG.  8 . The boxes  1001  to  1008  of FIG. 10 correspond to boxes  801 - 808  of FIG.  8 . Accordingly, the program flow and operation illustrated in those boxes will not be re-described. 
     The portion of the executive function subroutine within the dashed line  810  is specific to the USB interface and provides a second communication protocol. When an interrupt is issued by either the RS232 interface on the microcontroller  20  or the USB chip  42 , program flow passes to block  1011 . If  1011  the USB chip  42  requires service, data is read  1012  from the chip; and program flow passes to box  1013 . If  1011  the USB chip  42  does not require service, program flow passes to box  1002  for the function previously described. 
     The type of USB packet is determined  1013 . If the packet is a data packet, the data packet is copied  1014  into the command string; and control passes to the previously described block  1003 . If the packet is a control packet, the USB-specific control information is processed  1015 ; and program flow returns to the other processing  1001 . 
     The send-string routine is illustrated in FIG.  11  and is utilized to send information out of the unit  12  through the connector  40 . In a fashion similar to FIG. 10, the prior art portion of the send-string routine is outside of dashed line  1101 ; and the new portion of the send-string routine is inside the dashed line  1101 . 
     The prior art portion of the routine will be described first. Within the send-string routine  1102  the send character function  1103  is called for each character in the string. In the prior art send-character function, control passed directly from block  1103  to block  1104  as indicated by dashed line  1105 . In block  1104 , an individual character is placed  1104  in the hardware UART to begin transmission of the character. Program flow then passes to block  1106 , wherein the send-character subroutine is exited. 
     In the current send-character function, the program flow line  1105  of the prior art function is replaced by program flow lines  1112  and  1113 . Accordingly, program flow cannot pass directly from block  1103  to block  1104 . Upon initiation of the send character function, program flow passes to block  1110 . The blocks  1110  and  1111  additionally check for and handle USB transmissions. If  1110  the source is RS232, program flow passes to block  1104 . On the other hand, if  1110  the command is a USB command, program flow passes to block  1111 . The character is collected  1111  in the USB output buffer, and program flow passes to block  1106  wherein the send character-function is terminated. As noted in block  1111 , the entire string is collected in the USB chip  42  before the string is transmitted to the host computer in response to a request from the host computer. 
     The unit  10  of the present invention is capable of communicating with a host computer using one of a plurality of communication protocols. Although the present invention has been described in conjunction with the RS232 and USB protocols, the invention is not so limited. Any current or future communication protocol could be used in implementing the present invention. Also, although the present invention has been described in conjunction with two protocols, any number could be implemented by a routine extension of the disclosed methodology. 
     The individual protocol that an instrument  10  will use is determined by the cable  14  or  14 ′ connected to the handheld unit  12 . As illustrated in FIGS. 4-6, the appropriate pin-out connections are made as the connectors cable connector  54  or  54 ′ is physically interconnected with the unit connector  40 . The microcontroller  20  and the USB chip  42  are automatically and appropriately connected to the cable to implement the desired communication protocol. 
     Finally, it is possible that both protocols could be implemented through a single cable including all of the necessary pin-outs. Such an approach has proven to be particularly helpful during design, debugging, testing, and manufacturing planning. 
     The above description is that of a preferred embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the Doctrine of Equivalents.