Interfacing with a mouse - Revision history

Lynch at 07:54, 16 February 2009

2009-02-16T07:54:10Z

2009-02-12T20:03:51Z

2009-02-12T07:47:50Z

2009-02-12T07:37:24Z

added code section

2009-02-12T07:25:25Z

Mouse Interface

2009-02-12T07:24:52Z

Mouse Interface

2009-02-12T07:24:33Z

2009-02-12T07:18:41Z

2009-02-12T07:12:05Z

2009-02-12T06:56:18Z

Mouse Interface

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 | class="mbox-imageright" |
 |}
-== Original Assignment ==
-Interface the PIC with a PS/2 optical mouse and display (x,y) position data on either an LCD screen (see, e.g., [[C Example: Serial LCD]] or [[C Example: Parallel Interfacing with LCDs]]) or the PC (e.g., in Matlab or hyperterminal).
 == Overview ==

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+{| class="ambox ambox-notice"
+| class="mbox-image" |
+| class="mbox-text" | <div>
+'''This article documents an unfinished work.'''
+<br>Content may change as the project progresses.
+</div>
+| class="mbox-imageright" |
+|}
 == Original Assignment ==

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 }
 </pre>
+==Unresolved Issues==
-==Notes and References==
+Our group was unable to display the motion of an optical mouse on an LCD screen.  After a great deal of troubleshooting, we have come to the conclusion that our interrupt service routine algorithm or microcontroller is simply not fast enough to receive and send data in time with clock signal generated by the mouse.  The mouse clock signal is essentially a 10-16.7 kHz square wave.  Each high and each low on the clock signal would last roughly 40 microseconds and our interrupt service routine (which was supposed to trigger every time the clock went from high to low) tended to miss or skip several signals at a time. This problem prevented the mouse from ever receiving an “Enable Data Reporting” from the PIC and thus the mouse never outputted data to the PIC.
+Suggested solution: Use a faster microcontroller or develop a more efficient interface program.

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 When the clock is set low, the host will wait 10-25us before reading the data stream. More information on the mouse interface may be found at the following links:<br>
 [http://www.computer-engineering.org/ps2protocol/ Description of PS/2 Protocol by Adam Chapweske]<br>
-[http://www.allpinouts.org/index.php/Mouse/Keyboard_(PS/2) Description of Connector pinout for PS/2 Mouse/Keyboard]
+[http://www.allpinouts.org/index.php/Mouse/Keyboard_(PS/2) Description of Connector pinout for PS/2 Mouse/Keyboard by allpinouts.org]
 == Circuit ==

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 [[Image:2 Clock data pic.PNG|thumb|374px|center|Byte of Data[http://www.computer-engineering.org/ps2protocol/]]]
-When the clock is set low, the host will wait 10-25us before reading the data stream. More information on the mouse interface may be found at the following links:
+When the clock is set low, the host will wait 10-25us before reading the data stream. More information on the mouse interface may be found at the following links:<br>
-[http://www.computer-engineering.org/ps2protocol/ Description of PS/2 Protocol by Adam Chapweske]
+[http://www.computer-engineering.org/ps2protocol/ Description of PS/2 Protocol by Adam Chapweske]<br>
 [http://www.allpinouts.org/index.php/Mouse/Keyboard_(PS/2) Description of Connector pinout for PS/2 Mouse/Keyboard]
 == Circuit ==
 The relevant part of the breadboard adapter data sheet can be seen below.

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 == Mouse Interface ==
 Normally, when a mouse first powers on, it will send its device ID information and set default values for its sample rate, resolution and scaling.  The mouse also by default disables its ability to report data until it is sent an “Enable Data Reporting” command from the host (in this case the PIC).  Once the “Enable Data Reporting” bits are sent, data reporting is enabled, the mouse can send data as long as the clock and data line are not held low by the host.  Typically, a PS/2 mouse will send 3 bytes of data in three consecutive data packets as shown in the diagram below:
+[[Image:Mi table.PNG|thumb|374px|center|Mouse Interface Table [http://www.allpinouts.org/index.php/Mouse/Keyboard_(PS/2)]]]
+YV and XV are overflow flags for the motion in Y and X directions respectively where 0 means negative motion and 1 means positive motion.  R is for the right button and L is for the left button where 1 equals pressed and 0 equal unpressed.  X0-X7 and Y0-Y7 are binary outputs of 0 to 255, which represent how far the mouse has moved in its respective directions since the last sample (the least significant digit is on the right).  Optical mice with wheels and additional buttons generally send a fourth data packet, but for this lab, that data was not needed.
 == Circuit ==
 The relevant part of the breadboard adapter data sheet can be seen below.

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 On this page you will find the steps to use a PS/2 mouse's output to meet your needs. The code, circuit diagram, and notes about the interface are included. This is currently a work in progress, but should be a good foundation for those looking to build on it and be able to use a PS/2 mouse in their own projects.
+<br><br>
-== Mouse Interface ==
-<br><br><br><br><br><br><br><br><br><br><br>
 == PS/2 Protocol ==
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 [http://www.computer-engineering.org/ps2protocol/ Description of PS/2 Protocol by Adam Chapweske]
+== Mouse Interface ==
+Normally, when a mouse first powers on, it will send its device ID information and set default values for its sample rate, resolution and scaling.  The mouse also by default disables its ability to report data until it is sent an “Enable Data Reporting” command from the host (in this case the PIC).  Once the “Enable Data Reporting” bits are sent, data reporting is enabled, the mouse can send data as long as the clock and data line are not held low by the host.  Typically, a PS/2 mouse will send 3 bytes of data in three consecutive data packets as shown in the diagram below:
 == Circuit ==