Parallax 28560 User manual

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Cop right © Parallax Inc. Mouse Sensor Kit (#28560) v1.0 6/1/2010 Page 1 of 18
Mouse Sensor Kit (#285 0)
The Parallax Mouse Sensor is a module in kit form which, when assembled, provides the tracking
functions of an optical mouse. The two-wire serial interface is directly compatible with the Parallax ASIC
Stamp
®
2 family, the Parallax Propeller, and other microcontrollers.
Features
 Compact module, including illumination, optics, and custom laser-cut base
 “Close-to-the-metal” register-based serial interface for maximum flexibility
 Holes for mounting to other equipment
 Compatible with any S2-family ASIC Stamp
®
, the SX, and the Parallax Propeller
 Accommodation for single or dual three-wire (servo-type) interface cables
Key Specifications
 Power requirements: 5 VDC at 35 mA
 Communication: Two-wire serial (clock and data)
 Logic compatible with 3.3V (using external resistor) and 5V microcontrollers
 Dimensions: 1.80” (45.7mm) L x 1.00” (25.4 mm) W x 0.65” (16.5 mm) H
Application Ideas
 Measuring X and Y displacement on a flat surface
 Detecting vibration in two dimensions over a flat surface
What Comes with the Kit
Part Parallax No. Description Illustration (not to scale) Quan.
300-28560 Printed circuit board 1
U1 604-28560 MCS-12086 mouse
sensor chip
120
8
6
0
9
3
4
1
1
LED1 350-00031 Red T1¾ LED (lens
ma be red or clear) 1
350-00032 Right-angle LED holder 1
721-28560 Clear plastic lens/light
guide 1
D1 501-00008 1N5817 Schottk diode 1
R1, R2 150-01021 1K 1/8 W resistor
(brown, black, red) 2
R3 150-01022 100Ω 1/8 W resistor
(brown, black, brown) 1

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Part Parallax No. Description Illustration (not to scale) Quan.
C1 201-01070
100 µF aluminum
electrol tic capacitor
(color ma var ) 1
C2, C3 201-01063
0.1 µF ceramic
capacitors (marked
“104”)
1
0
4
2
J1 450-00104 2 x 3 header (2mm) 1
452-00057 2mm shunts 2
J2 450-00105 2x3 header (0.1”) 1
721-00011 Two-piece black Delrin
rectangular base set
1
700-00089 Black plastic snap
rivets 4
710-00028 #2 x ¼” Phillips pan
head machine screws 4
711-00004 #2 hex nuts 4
713-00018 White n lon spacers 4
Additional Parts for Interfacing
805-00002 14” servo extension
cable
2
451-00303 3-pin header 2
500-00008 2N3904 NPN transistor
(marked 2N3904) 1
500-00003 2N3906 PNP transistor
(marked 2N3906) 1
150-02200 2.2K ¼ W resistors
(red, red, red) 3
150-04710 470Ω ¼ W resistor
( ellow, violet, brown) 1
What You Need to Provide
For Assembly
• Fine-tipped soldering iron and small diameter (1/32”) rosin-core solder (lead-free or leaded)
• Wire clippers
• Needle-nosed pliers
• 99% isopropyl alcohol and an old (clean) toothbrush
• Miniature (#0) Phillips screwdriver
• Pointed tweezers
• Eye protection

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For Operation
• ASIC Stamp, Propeller, SX, etc.
• Carrier board (e.g. oard of Education, Propeller Demo oard, Propeller Proto oard, etc.)
• One or two servo extension cables with 3-pin headers (e.g. Parallax #805-00011)
Assembly Instructions
Assemble the Circuit Board
1. The printed circuit board is marked on top with the part numbers from the “Part” column in the
table above. Here is an illustration of the unpopulated circuit board:
2. Install and solder all the parts, except U1 and LED1, as shown below, paying close attention to
the polarity of D1 (stripe goes to the right) and of C1 (positive lead – the longer one – goes to
the top). Take your time and make sure that all parts are firmly seated against the board. For J1
and J2, solder the diagonal corner pins first and check the seating. If a header is crooked or not
all the way in, you have a chance to reheat the joints and make adjustments. Once these
headers are seated correctly, you can solder the remaining pins. Here’s what the board will look
like:
3. Take the LED and insert it into the right-angle holder, being sure to position the longer, positive
lead as shown:
4. With the needle-nosed pliers, grab the leads and pull the LED against the holder until it’s firmly
seated. Then, still pulling with the pliers, bend the leads sharply downward:
NOTE: The LED is shown in the drawings with a red lens. The LED provided may be red or clear.

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5. Now you can solder the LED assembly to the board. Here’s what the board will look like:
6. At this point, the board is completely assembled, except for U1, the sensor chip . Make sure to
clip all the leads that protrude through the board close to, but not completely flush with, the
bottom of the board.
7. Use the isopropyl alcohol and the toothbrush to clean any residual flux from the board. This is
the last chance you’ll get to clean it, so do a thorough job.
Assemble the Base
NOTE: The mechanical assembly involves some very tiny parts that can easily become lost if
dropped. Work in a location such that, if you do drop something, you will be able to find it again.
Working on top of a folded towel can help to avoid parts bouncing and getting lost.
1. There are two Delrin base pieces, a top piece and a bottom piece. The bottom of the bottom
piece may or may not have four engraved recesses in it:
2. Peel off any protective film that may be in place over these pieces (one side), and poke out any
“hanging chads” that may remain in some of the holes.
3. Stack the top piece over the bottom piece, maintaining the orientations shown above, so that you
can still see the engraved recesses, if there are any. The hexagonal holes in the bottom piece will
align with the slotted cutouts in the top piece. Insert the black plastic snap rivets into the corner
holes, so that the heads rest in the engraved recesses:

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4. Firmly press the heads of the snap rivets into place so they rest against the recesses created for
them. Their prongs will then spread to hold the two pieces together:
5. Place the base assembly rivet-head-side-down on the bench, and drop the clear plastic lens-and-
light guide into the rectangular recess created for it:
6. (See note below for an alternative to steps 6 and 7.) Place the assembled circuit board over the
base assembly, so that the little nibs from the rivets fit into the corner holes of the circuit board.
The end of the LED should be very near or just touching the lens assembly:
7. Now comes the tedious part. Using the tweezers, slip a nylon spacer between the circuit board
and the base assembly, so that it is centered on one of the four small holes. Install a #2 screw
from the top, through the circuit board, spacer, and base assembly. Take one of the hex nuts,
and insert it into the pocket in the bottom of the base assembly. While holding it in place with
your thumb, start the screw into it with a Phillips screwdriver. Do no tighten. Repeat for the other
three spacers, screws, and nuts. Then tighten all four screws. This is what the assembly will look
like, top and bottom:
NOTE: As an alternative to steps 6 and 7 above, you can first center the spacers over the holes
in the base, then position the circuit board on top of these, and simply drop the screws through
the holes. The nuts can then be installed from the bottom, one at a time, and the screws
tightened.

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Back to Soldering
The last step in the assembly process is to solder in the sensor chip. It was delayed until this point, so
that it will mate properly with the lens. Here’s what to do:
1. On the bottom of the chip, there is a small circle of clear yellow tape covering a hole. With the
tweezers, very carefully remove this tape. From this point onward, be very careful not to let any
foreign substances enter the hole.
2. Position the chip so that its pin #1 (indicated by a very small and subtle dimple) aligns with the
circled pad on the circuit board. Insert the chip into the lead holes:
3. Press the chip into the board as far as you can. It will probably touch the lens assembly, which is
good.
4. Making sure the chip is level with the board , solder one of its corner pins from the top side of the
board.
5. While applying finger pressure to the chip, remelt the solder at the corner you’ve just soldered to
make sure the chip is seated as far as it will go. Check again to make sure the chip is still level. It
may take several tries, but it’s important to get this right.
6. Solder the remaining seven pins from the top of the board.
7. You’re finished! Well, almost. You’ve still got two shunts to install, but we’ll get to that in the next
section.
Quick Start Circuit (BASIC Stamp)
NOTE: oard of Education users can simply connect using two extension cables from the onboard
servo headers. Make sure that servo power is jumpered to Vdd and not Vin .

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Quick Start Circuit (Propeller)
NOTE: Do not omit the 2.2K resistor . It is required in order to limit the input voltage to the Propeller.
Connecting and Testing
Once the Mouse Sensor powers up, the red LED should come on. For a further indication that it’s
working, place the Mouse Sensor on a flat surface and keep it still for a second or two. While keeping an
eye on the LED, move it slightly. The LED should brighten just a little while the Mouse Sensor is moving,
then dim a little when it stops. This indicates that the Mouse Sensor is detecting motion.
BASIC Stamp 2 Series
To test the Mouse Sensor further with a ASIC Stamp, wire it as shown above. Then upload the program
mouse_monitor.bs2, shown at the end of this document and downloadable from the Mouse Sensor
product page (search "28560" at www.parallax.com). When run, a debug window will pop up, and you
should see a display that looks something like this:
The program accumulates the sensor’s X and Y displacement data to show the current position. It also
displays a “quality” figure, which indicates how textured the surface is that the sensor is looking at. The
higher the number, the better.
You can also monitor the mouse position graphically, using the program mouse_monitor.exe,
downloadable from the Mouse sensor product page. You will have to make a small change to
mouse_monitor.bs2 to do so. Just comment out the line that reads #DEFINE USE_DEBUG:
'#DEFINE USE_DEBUG 'Comment this out to use 38400 baud, instead o DEBUG.

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Then upload the P ASIC program, and start the .exe. Once the program finds the Mouse Sensor output,
you will see a display that looks like this:
The green dot keeps track of the sensor’s current X and Y position. The dX and dY strip charts track the
sensor’s instantaneous change in position. If you move the sensor too fast, a message that says
“OVERFLOW” will display. The background grid spacing is 250 sensor pixels. The default resolution for
the P ASIC program is about 500 d.p.i., which works out to 1/2” of travel per division.
One thing that quickly becomes obvious from using this program is that, while the Mouse Sensor is very
good at tracking relative motion, it does accumulate small errors when keeping track of absolute position.
To demonstrate this, make a small mark at the sensor’s current location, and reset the ASIC Stamp to
zero the position. Then move the sensor around on the surface, and return to the starting point. Is the
reported position (0, 0)?
Propeller
To test the Mouse Sensor with the Propeller chip, wire it as shown above. Then upload the program
ouseSensor onitor.spin shown at the end of this document and downloadable as an archive from
the Mouse Sensor product page. It makes use of the ouseSensor object, which can also be found in
the Propeller Object Exchange (obex.parallax.com). It is designed to be used with the
mouse_monitor.exe program, as shown above. You will find it to be a lot more responsive with the
Propeller than with the ASIC Stamp.

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Advanced Three-wire Connection
The Mouse Sensor includes circuitry to harvest its operating power from the clock line. This makes it
possible to interface to the Mouse Sensor with a three-wire servo-type extension cable. ecause of the
Mouse Sensor’s current requirements, however, some additional circuitry is required at the host end, as
described below. First, however, you will need to change the shunt configuration on the mouse sensor to
the following:
This connects the A input on the interface header to both the sensor chip’s clock line and to the power-
harvesting circuitry.
BASIC Stamp 2 Family
Here’s how to connect the ASIC Stamp for three-wire (servo cable) operation, using the additional parts
that come with the kit:
Using this circuit entails a change in the program, since the clock is now inverted from what it was. This
is easily accomplished by commenting out the line that says #DEFINE NEG_CLK:
'#DEFINE NEG_CLK 'Comment this out to use a the multiplexed clock and Vdd line.
You will notice that the program gives a much snappier performance with this setting, too. That’s
because the sensor chip requires a negative-going clock. To provide such a clock, the P ASIC program
must resort to bit-banging the clock and data lines, which can be quite slow. ut, with the above
circuitry, it can communicate with a positive-going clock, and that can be done with the much faster
SHIFTIN and SHIFTOUT instructions.
Propeller
The three-wire Propeller circuitry is a little more complicated than that of the ASIC Stamp. This is
because the Propeller outputs do not rise high enough to turn off a PNP transistor powered from +5V.
Therefore, an additional transistor is required to do the job. Here’s the circuit:

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The Spin program requires no changes to accommodate this new circuit. The reason is that the clock
signal is inverted twice.
Resources and Downloads
You may download free example and demo programs from the Mouse Sensor product page (search
"28560" at www.parallax.com). and from the Propeller Object Exchange (obex.parallax.com).
Device Information
Theory of Operation
The mouse sensor chip is actually a tiny camera that is continuously snapping pictures, comparing each
with the one before to detect movement. It works best on surfaces that have a visible texture. Texture
provides features that it can recognize from one snapshot to the next.
Communication with the chip takes place by reading and writing its internal registers. The most important
of these are listed below:
Address Type Description Range
$00 Read/Write
Operation Mode bits:
7: Set to 1 to reset chip; 0 (default) to operate.
6: Set to 1 for power down; 0 (default) to run.
$02 Read-only DX: Amount of change in X direction since last poll. -128 ($80) to
127 ($7F)
$03 Read-only DY: Amount of change in Y direction since last poll. -128 ($80) to
127 ($7F)
$04 Read-only Image quality: the higher the better. 0 ($00) to 255 ($FF)
$16 Read-only
Status bits:
7: Set to 1 if motion occurred since last poll.
4: Set to 1 if DY register overflowed since last poll.
3: Set to 1 if DX register overflowed since last poll.
0: Set to 1 for 500 dpi; 0 for 1000 dpi.
$1 Read/Write
Configuration bits:
7: Set to 1 for 500 dpi; 0 (default) for 1000 dpi.