Patent Publication Number: US-2018046270-A1

Title: Stylus with touch-sensitive retention clip

Description:
BACKGROUND 
     A stylus may be used to provide precise touch input to a touch sensing device. In particular, a stylus may be shaped to mimic a traditional writing utensil, such as a pen or pencil, thus allowing a user to provide accurate touch input in a familiar manner. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
     A stylus includes an elongate gripping member terminating at a writing tip, a communication interface housed within the elongate gripping member, a touch-sensitive retention clip extending from the elongate gripping member, and a controller housed within the elongate gripping member. The communication interface is configured to wirelessly communicate with a computing device. The controller is configured to detect a position or movement of a finger along a length of the touch-sensitive retention clip, and send to the computing device, via the communication interface, information based on the position or movement of the finger along the length of the touch-sensitive retention clip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a stylus providing touch input to a touch-sensitive display device. 
         FIG. 2  shows a stylus including a touch-sensitive retention clip. 
         FIGS. 3A-5B  show differently configured capacitive touch-sensitive retention clips that may be implemented in a stylus. 
         FIGS. 6A and 6B  show a resistive touch-sensitive retention clip that may be implemented in a stylus. 
         FIG. 7  shows a resistive touch-sensitive retention clip that may be implemented in a stylus. 
         FIG. 8  shows a scenario in which zooming functionality is enabled via touch input to a touch-sensitive retention clip of a stylus. 
         FIG. 9  shows a scenario in which scrolling functionality is enabled via touch input to a touch-sensitive retention clip of a stylus. 
         FIG. 10  shows a computing system. 
     
    
    
     DETAILED DESCRIPTION 
     A stylus allows a user to interact with the display of a computing device via touch input. However, in some cases, touch input on the display may not be the most convenient form of user interaction with a computing device. For example, in order to perform a scrolling operation with a stylus via touch input, a user may have to touch the stylus to a scroll bar that is visually presented on a touch-sensitive display. In doing so, the user may have to make small and precise adjustments to the scroll bar that may be difficult to perform. In contrast, a scroll wheel of a mouse device may provide faster and more convenient scrolling functionality for document reading, internet browsing, and other computing device interactions. As such, a user may choose to use a mouse device to interact with a computing device, instead of, or in addition to using a stylus. 
     Accordingly, the present disclosure is directed a stylus that includes a touch-sensitive retention clip. The stylus may be configured to detect a position or movement of a finger along a length of the retention-clip. Further, the stylus may be configured to send information to a computing device based on the detected position or movement of the finger along the length of the touch-sensitive retention clip. As the finger changes position or moves along the length of the retention clip, the information that is sent to the computing device changes to reflect the change in position. Such information may be used by the computing device to effectuate computing operations, such as scrolling or zooming operations. By providing a touch-sensitive retention clip on the stylus, the stylus is able to provide scrolling, zooming, and/or other computing functionality in a manner that is similar to a scroll wheel of a mouse device. As such, a user may forgo using a mouse device in favor of the stylus when interacting with a computer. 
       FIG. 1  shows a stylus  100  interacting with a touch-sensitive display device  102 . The touch-sensitive display device  102  includes a touch sensor  104  configured to detect touch input from one or more touch sources, such as the stylus  100 . The touch sensor  104  may be configured to detect active and/or passive touch input, and the stylus  100  may be cooperatively configured to provide active and/or passive touch input. When active touch input is enabled, the stylus  100  may be configured to generate an electrical signal that is detected by the touch sensor  104 . In other implementations, the stylus  100  may be configured to provide passive touch input in which the stylus  100  does not produce an electrical signal corresponding to touch input. In another example, the touch sensor  104  may be configured to detect passive touch input from a finger of a user. The touch sensor  104  may be configured to receive input from input sources in direct contact with a surface of the touch-sensitive display device  102 , and/or, input from input sources not in direct contact with the touch-sensitive display device  102  (e.g., input devices that hover proximate to a surface of the display). “Touch input” as used herein refers to both types of input. The touch sensor  104  may take any suitable form including, but not limited to, one or more of a capacitive touch sensor and/or display, a resistive touch sensor and/or display, and an optical touch sensor and/or display. In one example, the touch sensor  104  includes a matrix of electrodes that form capacitors whose capacitances may be evaluated in detecting touch input. 
     Furthermore, the stylus  100  may be configured to provide user input to the touch-sensitive display device  102  in forms other than direct touch input that is detected by the touch sensor  104 . The touch-sensitive display device  102  may be configured to visually present appropriate graphical output  106  in response to receiving information from the stylus  100 . Such information may be based on touch input as well as other user input. While described with reference to a touch-sensitive display device, stylus  100  may optionally be used with touch-sensing surfaces that do not include display functionality. 
       FIG. 2  schematically shows a stylus  200  including mechanisms that enable various forms of user input to a computing device, such as the touch-sensitive display device  102  of  FIG. 1 . The stylus  200  is an example of the stylus  100  of  FIG. 1 . The stylus  200  is an active stylus shown in simplified form. The stylus  200  includes an elongate gripping member  202  terminating at an electrode writing tip  204  on one end and an electrode eraser  206  on an opposing end. The elongate gripping member  202  is cylindrical. However, the elongate gripping member  202  may assume any suitable size and/or shape. The electrode writing tip  204  and the electrode eraser  206  may be electrically conductive and configured to receive current when proximate to a driven electrode of a touch sensor, such as touch sensor  104  of  FIG. 1 . 
     In some implementations, the electrode writing tip  204  includes a pressure sensor  208  configured to detect a pressure when the electrode writing tip  204  is pressed against a surface. Likewise, the electrode eraser  206  includes a pressure sensor  210  configured to detect a pressure when the electrode eraser  206  is pressed against a surface. In one example, each of the pressure sensors  208  and  210  are force sensitive resistors. A touch pressure value of each of the respective pressure sensors  208  and  210  may be sent to a controller  212  that is housed in the elongate gripping member  202 . The controller  212  may be configured to derive touch input information from the output of the pressure sensors  208  and  210 . 
     The stylus  200  may be configured to operate in a receive mode and a drive mode. The receive mode may be employed (1) to synchronize the stylus  200  with a computing device/touch sensor to establish/maintain a shared sense of time; and (2) to establish a position (e.g., the Y coordinate of an electrode matrix or the X coordinate in the event of vertically-oriented rows) of the stylus  200  with respect to the touch sensor. During the receive mode, the touch sensor drives row electrodes of the electrode matrix to generate a position signal that is received by the electrode writing tip  204  or electrode eraser  206  of the stylus  200 . During the drive mode, the stylus  200  may drive the electrode writing tip  204  or the electrode eraser  206  to generate an electrical signal corresponding to touch input. The electrical signal may influence electrical conditions on one or more column electrodes of the electrode matrix of the touch sensor to, thereby establish the X position of the stylus  200  relative to the touch sensor. In particular, the shared sense of timing between the stylus  200  and the touch-sensitive display device allows the stylus  200  and the touch-sensitive display device to know which row of the electrode matrix the stylus  200  was closest to, thereby establishing the Y position of the stylus  200 . 
     Furthermore, the stylus  200  includes user input mechanisms other than touch input mechanisms (e.g., electrode tip and electrode eraser) that enable touch input to be provided directly to a touch-sensitive surface of a touch-sensitive display device. In particular, the stylus  200  includes barrel switch buttons  216 A and  216 B, and a touch-sensitive retention clip  218 , each of which are operatively coupled to the controller  212 . 
     The barrel switch buttons  216 A and  216 B protrude from the elongate gripping member  202 . The barrel switch buttons  216 A and  216 B are configured to be depressable to provide user input. In particular, a state (e.g., depressed or undepressed) of each barrel switch button  216 A.  216 B may be sent to the controller  212 . The state of the barrel switch buttons  216 A and  216 B may correspond to any suitable user input information. 
     The touch-sensitive retention clip  218  extends from the elongate gripping member  202 . The touch-sensitive retention clip  218  mechanically functions to physically retain the stylus  200  to another object. For example, the touch-sensitive retention clip  218  may temporarily couple the stylus to a user&#39;s pocket, a mobile device, or other object in order for a user to keep track of the stylus  200 . 
     Furthermore, the touch-sensitive retention clip  218  is electrically connected to a touch sensor  214  to enable detection of touch input on a surface of the touch-sensitive retention clip  218 . In particular, a presence of a finger on the touch-sensitive retention clip  218  may influence an electrical signal measured by the touch sensor  214 . The controller  212  may be configured to receive the electrical signal measured by the touch sensor  214 , and detect touch input by the finger on the touch-sensitive retention clip  218  based on the measured electrical signal. The detected touch input provided by the finger on the touch-sensitive retention clip  218  may correspond to any suitable user input information useable by a computing device to effectuate any suitable computing operation. Non-limiting examples of such information include, but are not limited to position information, movement information, gesture information (e.g., scroll direction and speed), and sensor signal information. 
     In the depicted implementation, the touch sensor  214  is housed in the elongate gripping member  202 . In other implementations, the touch sensor  214  instead may be integrated into the touch-sensitive retention clip  218 . 
     In some implementations, the touch sensor  214  may include a capacitive sensor configured to measure a capacitance of the touch-sensitive retention clip  218 . In such implementations, the controller  212  is configured to detect the position of the finger or movement of the finger along the length of the touch-sensitive retention clip  218  based on the capacitance measured by the capacitive sensor. In one example, the capacitance may be measured between the interior conductive material and ground. In another example, the capacitance may be measured between two different interior conductive materials having different electrical conductivities. 
     In other implementations, the touch sensor  214  may include a resistive sensor configured to measure a resistance of the touch-sensitive retention clip  218 . In such implementations, the controller  212  is configured to detect the position of the finger along the length of the retention clip based on the resistance measure by the resistive sensor. In one example, the resistance may be measured between two resistive electrodes. 
     Furthermore, in some implementations, the touch-sensitive retention clip  218  may include a plurality of different materials having different electrical properties. The shape of one or more of the plurality of materials may vary over a length (L) of the touch-sensitive retention clip  218 . Such material changes may enable a position of the finger along the length (L) of touch-sensitive retention clip  218  to be detected by the controller  212 . In particular, the electrical signal measured by the touch sensor  214  may vary relative to the position of the finger along the length (L) of the touch-sensitive retention clip  218 . Different configurations of the touch-sensitive retention clip  218  that enable such finger position detection are discussed in further detail below with reference to  FIGS. 3-6 . 
     The detected touch input provided by the finger on the touch-sensitive retention clip  218  may correspond to any suitable user input information useable by a computing device to effectuate any suitable computing operation. In one example, the barrel switches  216 A and  216 B, and the touch-sensitive retention clip  218  mimic at least some of the functionality of a mouse device. In particular, user input information derived from user interaction with the barrel switches  216 A and  216 B may be interpreted by a computing device to produce control commands similar to left and right buttons of a mouse device, and user input information derived from user interaction with the touch-sensitive retention clip  218  may be interpreted by a computing device to produce control commands similar to a scroll wheel of a mouse device. 
     The stylus  200  may transmit information (e.g., touch input/position or movement information, other user input information, stylus information) to the touch-sensitive display device via a communication interface  220 . The communication interface  220  is configured to communicatively couple the stylus  200  with one or more touch-sensitive display devices or other computing devices. The communication interface  220  may be housed in the elongate gripping member  202 . The communication interface  220  may include any suitable wireless communication hardware. In one example, the communication interface  220  includes a personal area network transceiver (e.g., a Bluetooth transceiver). In another example, the communication hardware establishes an electrostatic communication channel between the stylus  200  and a touch-sensitive display device through a capacitive coupling of the electrode writing tip  204  or the electrode eraser  206  and one or more electrodes of a touch sensor of the touch-sensitive display device. The communication interface  220  may employ any suitable type and/or number of different communication protocols to communicatively couple the stylus  200  with a touch-sensitive display device or other computing device. 
     The controller  212  may include any suitable computing hardware. In one example, the controller  212  includes a logic machine and a storage machine configured to hold instructions executable by the logic machine to perform various operations discussed herein. Such computing componentry is discussed in further detail below with reference to  FIG. 9 . 
     In one example, the controller  212  may be configured to detect a position or movement of a finger along a length of the touch-sensitive retention clip  218  based on an electrical signal measured by the touch sensor  214 , and send to a computing device, via the communication interface  220 , information based on the position or movement of the finger along the length of the touch-sensitive retention clip  218 . The information may correspond to any suitable control command. In one example, the information associated with the detected position or movement of the finger on the touch-sensitive retention clip  218  includes zoom information useable by the computing device to effectuate a zooming operation, an example of which is discussed in further detail below with reference to  FIG. 8 . In another example, the information associated with the detected position or movement of the finger on the touch-sensitive retention clip  218  corresponds to a scrolling operation, an example of which is discussed in further detail below with reference to  FIG. 9 . 
     In some implementations, the controller  212  may be configured to maintain the stylus  200  in a power saving mode in which the stylus  200  does not communicate with a computing device via the communication interface  220 . Further, the controller  212  may be configured to, in response to detecting a gesture or movement of a finger on the touch-sensitive retention clip  218 , switch the stylus  200  from the power saving mode to an active mode in which the stylus  200  communicates with the computing device via the communication interface  220  based on detecting the finger on the touch-sensitive retention clip  218 . A gesture may include any suitable movement of the finger on the touch-sensitive retention clip that is recognized by the stylus  200 . Such movements may be associated with a defined meaning. 
     In some implementations, the controller  212  may be configured to detect a touch by a finger on the touch-sensitive retention clip  218  based on an electrical signal measured by the touch sensor  214 . The controller  212  may be configured to determine that the touch is an intentional touch based on the electrical signal corresponding to a sliding movement of the finger along the length of the retention clip. The controller  212  may be configured to determine that the touch is an incidental touch based on the measured electrical signal corresponding to a static position of the finger on the touch-sensitive retention clip  218  for greater than a threshold duration. If the controller  212  determines that the touch is an incidental touch, then the controller  212  may be configured to ignore the incidental touch by not sending information to the computing device based on the position of the finger corresponding to the incidental touch. 
     The controller  212  may be configured to perform any suitable operations based on detecting touch input along the length of the touch-sensitive retention clip  218 . 
       FIGS. 3-6  show different configurations of a touch-sensitive retention clip that enable variable position sensing of a finger along a length of the touch-sensitive retention clip. The different configurations may be employed in a stylus, such as the stylus  200  of  FIG. 2 . 
       FIG. 3A  shows a side view and  FIG. 3B  shows a plan view of a touch-sensitive retention clip  300  in the form of a wire having a “U” shape. The touch-sensitive retention clip  300  has a length extending between a tip end  301  and an eraser end  303 . The touch-sensitive retention clip  300  couples to the elongate gripping member of the stylus at the eraser end  303 . The touch-sensitive retention clip  300  includes an interior conductive material  302  and an exterior isolating material  304  that surrounds the interior conductive material  302 . The interior conductive material  302  has a greater electrical conductivity than the exterior isolating material  304 . The interior conductive material  302  may include any suitable conductive or partially conductive material. The exterior isolating material  304  may include any suitable low conductivity material. For example, the exterior isolating material  304  may include any sort of plastic, paint, or other electrically-isolating coating. 
     As depicted in  FIG. 3A , a thickness of the interior conductive material  302  changes along a length of the touch-sensitive retention clip  300 . In particular, a thickness of the internal conductive material  302  decreases moving along the length of the touch-sensitive retention clip  300  in the direction of the tip end  301 . Correspondingly, a thickness of the exterior isolating material  304  increases moving along the length of the touch-sensitive retention clip  300  in the direction of the tip end  301 . The interior conductive material  302  and the exterior isolating material  304  cooperatively change shape along the length of the touch-sensitive retention clip  300  to maintain a consistent external shape along the length of the touch-sensitive retention clip  300 . The external shape of the touch-sensitive retention clip  300  may take any suitable form (e.g., circular, rectangular). 
     The interior conductive material  302  is electrically connected to a capacitive sensor  306 . The capacitive sensor  306  is configured to measure a capacitance of the touch-sensitive retention clip  300  relative to a ground of the stylus. As shown in  FIG. 3A , because a distance between the interior conductive material  302  and a surface  308  of the touch-sensitive retention clip  300  varies along the length, the measured capacitance varies based on a position of a finger along the length of the touch-sensitive retention clip  300 . For example, if a finger is positioned towards the eraser end  303  where the internal conductive material  302  is thicker, the measured capacitance may be greater than a measured capacitance when the finger is positioned towards the tip end  301 . In particular, because the finger is closer to the internal conductive material  302  at the eraser end  303 , the finger draws more current and correspondingly increases the measured capacitance. In this manner, variable touch input information may be provided based on a position of a finger along the length of the touch-sensitive retention clip  300 . 
     In other implementations, the thickness of the internal conductive material  302  may increase moving along the length of the touch-sensitive retention clip  300  in the direction of the tip end  301 , and the thickness of the exterior isolating material  304  may decrease moving along the length of the touch-sensitive retention clip  300  in the direction of the tip end  301 . 
       FIG. 4A  shows a side view and  FIG. 4B  shows plan view of a touch-sensitive retention clip  400  in the form of a wire having a “U” shape. The touch-sensitive retention clip  400  has a length extending between a tip end  401  and an eraser end  403 . The touch-sensitive retention clip  400  couples to the elongate gripping member of the stylus at the eraser end  401 . The touch-sensitive retention clip  400  includes an interior conductive material  402  and an exterior isolating material  404  that surrounds the interior conductive material  402 . The interior conductive material  402  and the exterior isolating material  404  may have the same or similar electrical properties as the interior conductive material  302  and the exterior isolating material  304  of  FIG. 3 . 
     As shown in  FIG. 4A , a thickness of the interior conductive material  402  remains consistent along a length of the touch-sensitive retention clip  400 . However, a thickness of the exterior isolating material  404  decreases moving along the length of the touch-sensitive retention clip  400  in the direction of a tip end  401 . In other words, the exterior isolating material  404  is thicker at an eraser end  403  than at the tip end  401 . Due to the varying thickness of the exterior isolating material  404  along the length of the touch-sensitive retention clip  400 , an external/overall thickness of the touch-sensitive retention clip  400  varies along the length. 
     The interior conductive material  402  is electrically connected to a capacitive sensor  406 . The capacitive sensor  406  is configured to measure a capacitance of the touch-sensitive retention clip  400  relative to a ground of the stylus. As shown in  FIG. 4A , because a distance between the interior conductive material  402  and a surface  408  of the touch-sensitive retention clip  400  varies along the length, the measured capacitance varies based on a position of a finger along the length of the touch-sensitive retention clip  400 . For example, if a finger is positioned towards the tip end  401  where the external isolating material  404  is thinner, the measured capacitance may be greater than a measured capacitance when the finger is positioned towards the eraser end  403 . In particular, because the finger is closer to the internal conductive material  402  at the tip end  401 , the finger draws more current and correspondingly increases the measured capacitance. In this manner, variable touch input information may be provided based on a position of a finger along the length of the touch-sensitive retention clip  400 . 
     In other implementations, the thickness of the external conductive material  404  may increase moving along the length of the touch-sensitive retention clip  400  in the direction of the tip end  401 . 
       FIG. 5A  shows a side view and  FIG. 5B  shows a plan view of a touch-sensitive retention clip  500  having a trapezoidal shape. The touch-sensitive retention clip  500  has a length extending between a tip end  501  and an eraser end  503 . The touch-sensitive retention clip  500  couples to the elongate gripping member of the stylus at the eraser end  503 . The touch-sensitive retention clip  500  includes an interior conductive material  502  and an exterior isolating material  504  that surrounds the interior conductive material  502 . The interior conductive material  502  and the exterior isolating material  504  may have the same or similar electrical properties as the interior conductive material  302  and the exterior isolating material  304  of  FIG. 3 . 
     As shown in  FIG. 5A , a thickness of the interior conductive material  502  and a thickness of the exterior isolating material  504  both remain consistent along the length of the touch-sensitive retention clip  500 . However, due to the trapezoidal shape, as shown in  FIG. 5B , a width of the interior conductive material  502  decreases moving along the length from the eraser end  503  to the tip end  501 . Due to the consistent thickness and varying width of the interior conductive material  502  along the length of the touch-sensitive retention clip  500 , an overall amount of the interior conductive material  502  varies along the length. 
     The interior conductive material  502  is electrically connected to a capacitive sensor  506 . The capacitive sensor  506  is configured to measure a capacitance of the touch-sensitive retention clip  500  relative to a ground of the stylus. Because the overall amount of the interior conductive material  502  varies along the length, the measured capacitance varies based on a position of a finger along the length of the touch-sensitive retention clip  500 . For example, if a finger is positioned towards the eraser end  503  where the internal conductive material  502  is wider, the measured capacitance may be greater than a measured capacitance when the finger is positioned towards the tip end  501 . In particular, because the finger interacts with a greater amount of the internal conductive material  402  at the eraser end  503 , the finger draws more current and correspondingly increases the measured capacitance. In this manner, variable touch input information may be provided based on a position of a finger along the length of the touch-sensitive retention clip  500 . 
     Any suitable dimension of the touch-sensitive retention clip (or a particular material(s) of the touch-sensitive retention clip) may change along the length of the touch-sensitive retention clip to enable detection of a position of a finger along the length of the touch-sensitive retention clip. Moreover, multiple different dimensions of the touch-sensitive retention clip (or a particular material(s) of the touch-sensitive retention clip) may change along the length of the touch-sensitive retention clip to enable detection of a position of a finger along the length of the touch-sensitive retention clip. For example, a thickness of the internal conductive material and a thickness of the external isolating material may change of the length of the touch-sensitive retention clip. 
       FIGS. 6A and 6B  show a touch-sensitive retention clip  600  configured to resistively detect touch input. The touch-sensitive retention clip  600  includes a surface layer  602  spaced apart from a base layer  604  by a gap  606 . The surface layer  602  and the base layer  604  include conductive material. Further, the gap  606  includes a plurality of isolating spacers  608  configured to prevent the surface layer  602  from contacting the base layer  604  when no touch input is applied to the touch-sensitive retention clip  600 . The surface layer  602  is electrically connected to a resistive sensor  610  configured to measure a voltage corresponding to a resistance of the touch-sensitive retention clip  600 . The surface layer  602  is deformable based on touch input applied to the surface layer  602 , such that the surface layer  602  contacts the base layer  604  to change the resistance measured by the resistive sensor  610 . 
     1 In  FIG. 6A , no touch input is applied to the touch-sensitive retention clip  600 , so the surface layer  602  does not contact the base layer  604 . In this state, the resistive sensor  610  measures a first voltage that indicates no touch input. In  FIG. 6B , a finger  612  applies touch input to the surface layer  602  that causes the surface layer  602  to deform through the gap  606  to contact the base layer  604 . When the surface layer  602  contacts the base layer  604 , electrical current flows between the two layers to change the voltage measured by the resistive sensor  610  to a second voltage. A controller of the stylus may receive the voltage measurements of the resistive sensor  610 , and detect a position of the finger  612  along the length of the touch-sensitive retention clip  600  based on voltage measured by the resistive sensor  610 . 
     Further, the controller may infer a position of the finger along the length of the touch-sensitive retention clip  600  based on a change in voltage. For example, if the finger  612  applies touch input toward the open end of the touch-sensitive retention clip  600 , current flows through the surface layer  602  for a first distance to reach the resistive sensor  610 . That first distance corresponds to a first resistance that affects the voltage measured by the resistive sensor  610 . Further, if the finger  612  applies touch input toward the connected end of the touch-sensitive retention clip  600 , current flows through the surface layer  602  for a second distance that is shorter than the first distance to reach the resistive sensor  610 . This shorter second distance corresponds to a second resistance that is lower than the first resistance. Accordingly, the touch input applied towards the open end may have greater change in measured voltage relative to the touch input applied towards the connected end. In this manner, variable touch input information may be provided based on a position of a finger along the length of the touch-sensitive retention clip  600 . 
       FIG. 7  shows another touch-sensitive retention clip  700  configured to resistively detect touch input. The touch-sensitive retention clip  700  includes a first electrode  702  and a second electrode  704 . The first and second electrodes  702  and  704  may include any suitable conductive or semi-conductive material. For example, the first and second electrodes  702  and  704  may include carbon contaminated plastic. In some implementations, the electrical conductivity of the first and second electrodes  702  and  704  may be low so that small changes in finger position along the length of the touch-sensitive retention clip  700  produce measurable changes in resistance. 
     In the depicted implementation, the first and second electrodes  702  and  704  are separated by an isolating material  706 . In other implementations, the first and second electrodes  702  and  704  may be physically spaced apart from one another such that the first and second electrodes  702  and  704  are not connected. 
     The first and second electrodes  702  and  704  are electrically connected to a resistive sensor  708  configured to measure a resistance between the first and second electrodes  702  and  704 . The resistance measured by the resistive sensor  708  varies based on finger touch input along the length of the first and second electrodes  702  and  704 . For example, the measured resistance increases as the finger moves away from the restive sensor  708  and towards the isolating material  706 . In this manner, variable touch input information may be provided based on a position of a finger along the length of the touch-sensitive retention clip  700 . 
     The information sent from the stylus to the computing device based on the position or movement of the finger along the length of the touch-sensitive retention clip may be associated with any suitable functionality, control commands, or other computing operations.  FIGS. 8 and 9  show different scenarios in which touch input to a touch-sensitive retention clip of a stylus enable different computing functionality. 
       FIG. 8  shows a scenario in which zooming functionality is enabled via touch input to a touch-sensitive retention clip of a stylus  800 . The stylus  800  is in communication with a display device  802 . The display device  802  visually presents a scene of a city landscape. 
     At time T 1 , a finger  804  applies touch input to a first—i.e., “top” position of a touch-sensitive retention clip  806 . The stylus  800  sends information to the display device  802  based on the finger  804  being at the top position of the touch-sensitive retention clip  806 . In some implementations, the stylus  800  can process the information to determine a gesture (e.g., scroll direction and speed), and send the gesture to the display device  802 . The display device  802  associates the received information with a low zoom level operation, and the display device  802  visually presents the city landscape with a perspective corresponding to the low zoom level operation. 
     At time T 2 , the finger  804  slides down and applies touch input to a second—i.e., “middle” position of the touch-sensitive retention clip  806 . The stylus  800  sends information to the display device  802  based on the finger  804  being at the middle position of the touch-sensitive retention clip  806 . The display device  802  associates the received information with a medium zoom level operation, and the display device  802  visually presents the city landscape with a perspective corresponding to the medium zoom level operation. In other words, the display device  802  zooms in on the city landscape relative to the perspective visually presented at time T 1 . 
     At time T 3 , the finger  804  slides down and applies touch input to a third—i.e., “bottom” position of the touch-sensitive retention clip  806 . The stylus  800  sends information to the display device  802  based on the finger  804  being at the bottom position of the touch-sensitive retention clip  806 . The display device  802  associates the received information with a high zoom level operation, and the display device  802  visually presents the city landscape with a perspective corresponding to the high zoom level operation. In other words, the display device  802  zooms in on the city landscape relative to the perspective visually presented at time T 2 . 
     This scenario is provided as an example. Zooming functionality may be implemented via the touch-sensitive retention clip  806  in any suitable manner. For example, in another implementation, the finger  804  may apply touch input to the bottom position of the touch-sensitive retention clip  806  to cause the display device to visually present the low zoom level of the city landscape. Further, the finger  804  may slide up the touch-sensitive retention clip  806  to the top position to cause the display device  802  to zoom in on the city landscape. In another example, the finger may slide along the length of the touch-sensitive retention clip  806  repeatedly to effectuate a repeated or extended zoom operation (in a manner similar to repeatedly rotating a scroll wheel of a mouse device). 
       FIG. 9  shows a scenario in which scrolling functionality is enabled via touch input to a touch-sensitive retention clip of a stylus  900 . The stylus  900  is in communication with a display device  902 . The display device  902  visually presents pages of a document. 
     At time T 1 , a finger  904  applies touch input to a first—i.e., “top” position of a touch-sensitive retention clip  906 . The stylus  900  sends information to the display device  902  based on the finger  904  being at the top position of the touch-sensitive retention clip  906 . The display device  902  associates the received information with a top scroll position, and the display device  902  visually presents PAGE 1 at the top of the document. 
     At time T 2 , the finger  904  slides down and applies touch input to a second—i.e., “middle” position of the touch-sensitive retention clip  906 . The stylus  900  sends information to the display device  902  based on the finger  904  being at the middle position of the touch-sensitive retention clip  906 . The display device  902  associates the received information with a middle scroll position, and the display device  902  visually presents PAGE 2 in the middle of the document. In other words, the display device  902  scrolls down the document relative to the perspective visually presented at time T 1 . 
     At time T 3 , the finger  904  slides down and applies touch input to a third—i.e., “bottom” position of the touch-sensitive retention clip  906 . The stylus  900  sends information to the display device  902  based on the finger  904  being at the bottom position of the touch-sensitive retention clip  906 . The display device  902  associates the received information with a bottom scroll position, and the display device  902  visually presents PAGE 3 at the bottom of the document. In other words, the display device  902  scrolls down the document relative to the perspective visually presented at time T 2 . 
     This scenario is provided as an example. Scrolling functionality may be implemented via the touch-sensitive retention clip  906  in any suitable manner. For example, in another implementation, the finger  904  may apply touch input to different positions of the touch-sensitive retention clip  906  to cause the display device  902  to scroll in different directions. For example, the finger  904  may apply touch input to the top position of the touch-sensitive retention clip  906  to scroll up, and the finger  904  may apply touch input to the bottom position of the touch-sensitive retention clip  906  to scroll down. 
       FIG. 10  schematically shows a non-limiting implementation of a computing system  1000  that can enact one or more of the methods and processes described above. Computing system  1000  is shown in simplified form. Computing system  1000  may take the form of one or more stylus controllers, personal computers, server computers, tablet computers, home-entertainment computers, network computing devices, gaming devices, mobile computing devices, mobile communication devices (e.g., smart phone), and/or other computing devices. For example, computing system  1000  is an example of the stylus  100  of  FIG. 1 , the display device  102  of  FIG. 1 , and the stylus  200  of  FIG. 2 , as well as other devices described herein. 
     Computing system  1000  includes a logic machine  1002  and a storage machine  1004 . Computing system  1000  may optionally include a display subsystem  1006 , input subsystem  1008 , communication subsystem  1010 , and/or other components not shown in  FIG. 10 . 
     Logic machine  1002  includes one or more physical devices configured to execute instructions. For example, the logic machine  1002  may be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions may be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwvise arrive at a desired result. 
     The logic machine  1002  may include one or more processors configured to execute software instructions. Additionally or alternatively, the logic machine  1002  may include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of the logic machine  1002  may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. Individual components of the logic machine  1002  optionally may be distributed among two or more separate devices, which may be remotely located and/or configured for coordinated processing. Aspects of the logic machine  1002  may be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration. 
     Storage machine  1004  includes one or more physical devices configured to hold instructions executable by the logic machine  1002  to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage machine  1004  may be transformed—e.g., to hold different data. 
     Storage machine  1004  may include removable and/or built-in devices. Storage machine  1004  may include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and/or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), among others. Storage machine  1004  may include volatile, nonvolatile, dynamic, static, read/write, read-only, random-access, sequential-access, location-addressable, file-addressable, and/or content-addressable devices. 
     It will be appreciated that storage machine  1004  includes one or more physical devices. However, aspects of the instructions described herein alternatively may be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration. 
     Aspects of logic machine  1002  and storage machine  1004  may be integrated together into one or more hardware-logic components. Such hardware-logic components may include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC/ASICs), program- and application-specific standard products (PSSP/ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example. 
     When included, display subsystem  1006  may be used to present a visual representation of data held by storage machine  1004 . This visual representation may take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine  1004 , and thus transform the state of the storage machine  1004 , the state of display subsystem  1006  may likewise be transformed to visually represent changes in the underlying data. Display subsystem  1006  may include one or more display devices utilizing virtually any type of technology. Such display devices may be combined with logic machine  1002  and/or storage machine  1004  in a shared enclosure, or such display devices may be peripheral display devices. 
     When included, input subsystem  1008  may comprise or interface with one or more user-input devices such as a keyboard, mouse, touch screen, or game controller. In some implementations, the input subsystem  1008  may comprise or interface with selected natural user input (NUI) componentry. Such componentry may be integrated or peripheral, and the transduction and/or processing of input actions may be handled on- or off-board. Example NUI componentry may include a microphone for speech and/or voice recognition; an infrared, color, stereoscopic, and/or depth camera for machine vision and/or gesture recognition; a head tracker, eye tracker, accelerometer, and/or gyroscope for motion detection and/or intent recognition; as well as electric-field sensing componentry for assessing brain activity. 
     When included, communication subsystem  1010  may be configured to communicatively couple computing system  1000  with one or more other computing devices. Communication subsystem  1010  may include wired and/or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem  1010  may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some implementations, the communication subsystem  1010  may allow computing system  1000  to send and/or receive messages to and/or from other devices via a network such as the Internet. 
     In an example, a stylus comprises an elongate gripping member terminating at a writing tip, a communication interface housed within the elongate gripping member and configured to wirelessly communicate with a computing device, a touch-sensitive retention clip extending from the elongate gripping member, and a controller housed within the elongate gripping member and configured to: detect a position or movement of a finger along a length of the touch-sensitive retention clip, and send to the computing device, via the communication interface, information based on the position or movement of the finger along the length of the touch-sensitive retention clip. In this example, the stylus may further comprise a capacitive sensor electrically connected to the touch-sensitive retention clip, the capacitive sensor being configured to measure a capacitance of the touch-sensitive retention clip, and the controller may be configured to detect the position or movement of the finger along the length of the touch-sensitive retention clip based on the capacitance measured by the capacitive sensor. In this example, the touch-sensitive retention clip may include an interior conductive material and an exterior isolating material, and wherein the capacitive sensor is electrically connected to the interior conductive material. In this example, a thickness of the interior conductive material may change along the length of the touch-sensitive retention clip. In this example, a thickness of the exterior isolating material may vary along the length of the touch-sensitive retention clip. In this example, a width of the interior conductive material may change along the length of the touch-sensitive retention clip. In this example, a shape of the touch-sensitive retention clip may be trapezoidal. In this example, the stylus may further comprise a resistive sensor electrically connected to the touch-sensitive retention clip, the resistive sensor being configured to measure a resistance of the touch-sensitive retention clip, and the controller may be configured to detect the position or movement of the finger along the length of the touch-sensitive retention clip based on the resistance measured by the resistive sensor. In this example, the information may include scroll information. In this example, the information may include zoom information. In this example, the communication interface may include a personal area network transceiver. In this example, the controller may be further configured to: maintain the stylus in a power saving mode in which the stylus does not communicate with the computing device via the communication interface, and switch the stylus from the power saving mode to an active mode in which the stylus communicates with the computing device via the communication interface based on detecting movement of the finger on the touch-sensitive retention clip. 
     In an example, a stylus comprises an elongate gripping member terminating at a writing tip, a communication interface housed within the elongate gripping member and configured to wirelessly communicate with a computing device, a touch-sensitive retention clip extending from the elongate gripping member, a capacitive sensor electrically connected to the touch-sensitive retention clip, the capacitive sensor being configured to measure a capacitance of the touch-sensitive retention clip, and a controller configured to: detect a position or movement of a finger along a length of the touch-sensitive retention clip based on a capacitance measured by the capacitive sensor, and send to the computing device, via the communication interface, information based on the position or movement of the finger along the length of the touch-sensitive retention clip. In this example, the touch-sensitive retention clip may include an interior conductive material and an exterior isolating material, and the capacitive sensor may be electrically connected to the interior conductive material. In this example, a thickness of the interior conductive material may change along the length of the touch-sensitive retention clip. In this example, a thickness of the exterior isolating material may vary along the length of the touch-sensitive retention clip. In this example, a width of the interior conductive material may change along the length of the touch-sensitive retention clip. In this example, the information may include scroll information. In this example, the information may include zoom information. 
     In an example, a stylus comprises an elongate gripping member terminating at a writing tip, a communication interface housed within the elongate gripping member and configured to wirelessly communicate with a computing device, a touch-sensitive retention clip extending from the elongate gripping member, the touch-sensitive retention clip including an interior conductive material and an exterior isolating material, and wherein one or more dimensions of the interior conductive material changes along a length of the retention clip, a capacitive sensor electrically connected to the touch-sensitive retention clip the capacitive sensor being configured to measure a capacitance of the touch-sensitive retention clip, and a controller configured to: detect a position or movement of a finger along a length of the touch-sensitive retention clip based on a capacitance measured by the capacitive sensor, and send to the computing device, via the communication interface, information based on the position or movement of the finger along the length of the touch-sensitive retention clip. 
     It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific implementations or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed. 
     The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.