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+PIU Notes
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+===
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+
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+These are notes for the a PIU upgrade to include
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+newer hardware.
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+
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+Overview
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+---
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+
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+The PIU should be able to accept a variety of fare media,
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+including magstripe cards (multiple track), RFIDs (125kHz and
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+Mifare) and barcode/QR codes using a camera.
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+
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+The display should be such that communication is given back to
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+the rider.
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+The camera can also be used to potentially help with QR code alignment to
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+the (down facing) camera.
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+
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+There's some investigation that should be done in terms of what, if any,
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+gets offloaded to a microcontroller but the basic idea is:
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+
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+* The Raspberry Pi (Zero) manages the HID devices, camera and screen
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+* The camera can be used to scan for QR codes
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+* For QR code scanning, a passthrough of the camera to the screen can
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+ be used for alignment
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+* The touch screen can be used for confirmation if need be
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+* Whatever is used for communication back to the DIU can use the same
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+ protocol already in place
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+
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+By having a microcontroller (Arduino, say) that's in charge of communication or
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+the RFID and Magstripe devices, this provides an 'instant on' for that portion
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+of the PIU.
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+Putting everything behind the Raspberry Pi is conceptually simpler but is sluggish
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+to boot up.
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+
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+Requirements
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+---
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+
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+* Housing
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+* 12-24v in (requires buck converter)
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+* Display
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+* RFID reader (125kHz and Mifare?)
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+* Magstripe reader (3 tracks)
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+* Camera
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+* Arduino
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+
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+RFID Reader
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+---
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+
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+Some electronics speak "Wiegand Protocol".
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+
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+There's an Arduino library that has appropriate code (from [monkeyboard](https://github.com/monkeyboard/Wiegand-Protocol-Library-for-Arduino)).
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+
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+I'm also unclear as to what the current system RFID media uses.
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+
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+Display
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+---
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+
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+There's a [2.8 inch touch display](http://www.raspberrypiwiki.com/index.php/2.8_inch_Touch_Screen_for_Pi_zero) that could be a candidate ([MZDPI](https://github.com/tianyoujian/MZDPI)).
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+
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+Apparently there's a simple install script:
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+
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+```
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+cd ~/
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+git clone https://github.com/tianyoujian/MZDPI.git
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+cd MZDPI/vga
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+sudo chmod +x mzdpi-vga-autoinstall-online
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+sudo ./mzdpi-vga-autoinstall-online
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+sudo reboot
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+```
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+
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+Camera
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+---
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+
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+I would recommend a Pi NoIR that can be hooked into the Pi Zero ([Adafruit](https://www.adafruit.com/product/3100)).
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+
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+I've had success in getting it up and running with a Raspberry Pi Zero before and it might be easy to set up and fast enough to use.
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+
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+
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+
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+Notes
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+---
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+
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+Some of the peripherals act as keyboard input devices.
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+In order to not have them pollute input, they need to be
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+taken over by a process.
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+
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+[SO](https://stackoverflow.com/questions/1698423/how-can-you-take-ownership-of-a-hid-device) has
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+an article on it.
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+More investigation needs to be done but the basics look to be:
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+
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+* Use the "event device interface" `/dev/input/event*` to look for the device
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+* Use an `ioctl` `EVIOCGRAB` call to get exclusive use of the device
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+
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+---
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+
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+```
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+cat /proc/bus/input/devices | grep -P '^[NH]: ' | paste - -
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+```
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+
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+---
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+
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+There's a [Python tutorial](https://python-evdev.readthedocs.io/en/latest/tutorial.html) that looks to have an easy way to do this:
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+
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+```
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+import evdev
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+import asyncio
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+dev = {}
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+
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+evfns = [ "/dev/input/event0", "/dev/input/event1", ... , "/dev/input/event12" ]
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+
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+for evfn in evfns:
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+ _dev = evdev.InputDevice(evfn)
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+ if dev.name == HID_NAME:
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+ dev = _dev
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+ break
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+
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+dev.grab()
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+
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+async def print_events(device):
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+ async for event in device.async_read_loop():
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+ print(device.path, evdev.categorize(event, sep=': ')
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+
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+for device in dev:
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+ asyncio.ensure_future(print_events(dev))
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+
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+...
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+
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+```
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+
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+The above has to be played around with but it looks like the seeds are there.
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+
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+
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+References
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+---
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+
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+* [SO: Ownership of HID device](https://stackoverflow.com/questions/1698423/how-can-you-take-ownership-of-a-hid-device)
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+* [Python evdev tutorial](https://python-evdev.readthedocs.io/en/latest/tutorial.html)
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+* [GitHub: monkeyboard/Wiegand-Protocol-Library-for-Arduino](https://github.com/monkeyboard/Wiegand-Protocol-Library-for-Arduino)).
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+* [2.8 inch touch display](http://www.raspberrypiwiki.com/index.php/2.8_inch_Touch_Screen_for_Pi_zero)
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+* [GitHub: tianyoujian/MZDPI](https://github.com/tianyoujian/MZDPI)
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+
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