130 lines
4.8 KiB
ReStructuredText
130 lines
4.8 KiB
ReStructuredText
Making the pyboard act as a USB mouse
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=====================================
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The pyboard is a USB device, and can configured to act as a mouse instead
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of the default USB flash drive.
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To do this we must first edit the ``boot.py`` file to change the USB
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configuration. If you have not yet touched your ``boot.py`` file then it
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will look something like this::
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# boot.py -- run on boot-up
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# can run arbitrary Python, but best to keep it minimal
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import pyb
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#pyb.main('main.py') # main script to run after this one
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#pyb.usb_mode('CDC+MSC') # act as a serial and a storage device
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#pyb.usb_mode('CDC+HID') # act as a serial device and a mouse
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To enable the mouse mode, uncomment the last line of the file, to
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make it look like::
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pyb.usb_mode('CDC+HID') # act as a serial device and a mouse
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If you already changed your ``boot.py`` file, then the minimum code it
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needs to work is::
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import pyb
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pyb.usb_mode('CDC+HID')
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This tells the pyboard to configure itself as a CDC (serial) and HID
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(human interface device, in our case a mouse) USB device when it boots
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up.
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Eject/unmount the pyboard drive and reset it using the RST switch.
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Your PC should now detect the pyboard as a mouse!
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Sending mouse events by hand
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----------------------------
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To get the py-mouse to do anything we need to send mouse events to the PC.
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We will first do this manually using the REPL prompt. Connect to your
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pyboard using your serial program and type the following::
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>>> pyb.hid((0, 10, 0, 0))
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Your mouse should move 10 pixels to the right! In the command above you
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are sending 4 pieces of information: button status, x, y and scroll. The
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number 10 is telling the PC that the mouse moved 10 pixels in the x direction.
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Let's make the mouse oscillate left and right::
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>>> import math
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>>> def osc(n, d):
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... for i in range(n):
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... pyb.hid((0, int(20 * math.sin(i / 10)), 0, 0))
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... pyb.delay(d)
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...
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>>> osc(100, 50)
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The first argument to the function ``osc`` is the number of mouse events to send,
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and the second argument is the delay (in milliseconds) between events. Try
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playing around with different numbers.
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**Excercise: make the mouse go around in a circle.**
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Making a mouse with the accelerometer
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-------------------------------------
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Now lets make the mouse move based on the angle of the pyboard, using the
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accelerometer. The following code can be typed directly at the REPL prompt,
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or put in the ``main.py`` file. Here, we'll put in in ``main.py`` because to do
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that we will learn how to go into safe mode.
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At the moment the pyboard is acting as a serial USB device and an HID (a mouse).
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So you cannot access the filesystem to edit your ``main.py`` file.
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You also can't edit your ``boot.py`` to get out of HID-mode and back to normal
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mode with a USB drive...
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To get around this we need to go into *safe mode*. This was described in
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the [safe mode tutorial](tut-reset), but we repeat the instructions here:
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1. Hold down the USR switch.
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2. While still holding down USR, press and release the RST switch.
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3. The LEDs will then cycle green to orange to green+orange and back again.
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4. Keep holding down USR until *only the orange LED is lit*, and then let
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go of the USR switch.
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5. The orange LED should flash quickly 4 times, and then turn off.
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6. You are now in safe mode.
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In safe mode, the ``boot.py`` and ``main.py`` files are not executed, and so
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the pyboard boots up with default settings. This means you now have access
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to the filesystem (the USB drive should appear), and you can edit ``main.py``.
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(Leave ``boot.py`` as-is, because we still want to go back to HID-mode after
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we finish editting ``main.py``.)
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In ``main.py`` put the following code::
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import pyb
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switch = pyb.Switch()
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accel = pyb.Accel()
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while not switch():
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pyb.hid((0, accel.x(), accel.y(), 0))
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pyb.delay(20)
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Save your file, eject/unmount your pyboard drive, and reset it using the RST
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switch. It should now act as a mouse, and the angle of the board will move
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the mouse around. Try it out, and see if you can make the mouse stand still!
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Press the USR switch to stop the mouse motion.
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You'll note that the y-axis is inverted. That's easy to fix: just put a
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minus sign in front of the y-coordinate in the ``pyb.hid()`` line above.
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Restoring your pyboard to normal
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--------------------------------
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If you leave your pyboard as-is, it'll behave as a mouse everytime you plug
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it in. You probably want to change it back to normal. To do this you need
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to first enter safe mode (see above), and then edit the ``boot.py`` file.
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In the ``boot.py`` file, comment out (put a # in front of) the line with the
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``CDC+HID`` setting, so it looks like::
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#pyb.usb_mode('CDC+HID') # act as a serial device and a mouse
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Save your file, eject/unmount the drive, and reset the pyboard. It is now
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back to normal operating mode.
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