Support for Ping (pulseIn Firmata) and other improvements #45
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NeoPolus
commented
Mar 30, 2016
NeoPolus
commented
- Support for pulseIn compatible Firmata, needed for ultrasonic ranging sensors that use a pulse to measure distances: the new "ping" method to the Pin class returns the echo time. An utility function to convert to distance was also added.
- Improved the Board class, now it supports the Python "with" statement to be able to automagically manage the Iterator thread (autostarts the iterator, and takes care to call board.exit()).
- Better support for working with timeouts (useful when the communication with the board hangs -thought that should no longer happen if we use the new 'with' support-).
This for example allows to use the timeout feature, added on tino#38 to the Board constructor, from the helper function.
Previously some timeouts (when reading from the board and not enought data was available) would raise a "TypeError: ord() expected a character, but string of length 0 found" exception, that is not very useful to know what's happening. Now it will raise a "IOError: Failed to read data from port, read N bytes expected M bytes" that is easier to understand and shows more information.
This enables using HC-SR04 ultrasonic ranging sensors easily (see http://www.micropik.com/PDF/HCSR04.pdf). Note: Requires pulseIn compatible Firmata in the arduino board (see https://github.com/jgautier/arduino-1/tree/pulseIn).
(To use with ultrasonic ranging sensors).
This will avoid problems with the exit() method not being called
(the __del__ exit() statement was not always called! causing the
connection with the board to hang if an Iterator thread was running).
Also it simplifies the code, as an Iterator will be managed
automagically for the with block.
board = Arduino('/dev/...')
with board: # an Iterator gets started automagically.
board.get_pin('d:8:i').read() # Works! as an Iterator is running.
# board.exit() gets called automagically and the Iterator stops
# after this line.
Use the same pin number in the text as in the sample HC-SR04 diagram, and show the units used.
"The significance of this flag is that the entire Python program exits when only daemon threads are left." This way Python won't hang at exit, but will just warn of an exception at shutdown instead. Anyway it's still better to call ``Board.exit()`` or use a ``with board: ...`` block to guarantee proper shutdown and avoid this warning.
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Hi, thanks for your extensive pull request. However, it is usually easier to implement features if they are small and contained. My reaction on these three proposals:
If you would like to move forward with one or more of these proposals, could you please do so in separate pull requests? Also, please take PEP8 (https://www.python.org/dev/peps/pep-0008/) into account (use 4 spaces instead of tabs, etc.). I use |
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So, what's the status on this? any chance that pyFirmata will get ping support at some point? |
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This one would be really helpful, any chance we can provide pulse in through a special flag? without pulsein ultrasonic is not usable in firmata. |
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What can we do to make this PR successful? |
