93 lines
4 KiB
YAML
93 lines
4 KiB
YAML
date: 2009-06-21
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title: Intelligent Drink Dispenser - Software Design
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---
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The other major half of the Intelligent Drink Dispenser project was the software side
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of things. As with the hardware, there were some things we had to consider when
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beginning the design of things.
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---
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What language should we use? Should this be a GUI
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application or web application? If we go with a GUI application, what operating system
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should we target?
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We decided that since we only had a semester to get everything done, we needed a
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framework to take care of the more nitty-gritty stuff. We eventually decided to go
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with the Django web framework, which uses the Python programming language. Python is
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a language we all knew and Jon and I had used Django in the past. Also, since our
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'final product' would be highly based on a client-server model, it makes sense to
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go with a web app since the server can be in a central location with many clients
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connecting to it.
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The most important thing to us was the fact that Django abstracts the database into models
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for us. No having to mess around with raw SQL, we just run some queries and get our data
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from the models as if they're just plain ol' objects. After some thought, we came up with
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our models and their relationships:
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The development of the application was fairly straight-forward. It was just a standard
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Django app after all. The interesting part was interfacing with the hardware.
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If you remember from my post talking about the hardware side, we used an FTDI UM232
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USB-to-serial converter. Lucky for us, there's a Linux kernel module which represents this
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device as a virtual serial port, which made our jobs a whole lot easier since there's
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existing serial libraries for Python (like pyserial). We ended up just writing a couple of
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functions, one to read the RFID tag from the serial port, and one that takes in a Drink id
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and then communicates to the microcontroller to pour it. The microcontroller's fairly dumb,
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just taking a number and turning that pin on, or turning all of the pins off if a non-valid
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character is sent, as you can see in the pourDrink function:
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def pourDrink(id, serialPort=DEVICE):
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"""Pours the drink given by the specified ID"""
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# Seconds per mL of the motors, found experimentally
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# These should be in the database or a config file instead of hardcoded...
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secondsPerML = []
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secondsPerML.append(9.858/350.0) # Pump 0
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secondsPerML.append(9.858/350.0) # Pump 1
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secondsPerML.append(6.385/210.0) # Pump 2
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components = DrinkComponent.objects.filter(drink=id)
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for c in components:
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stock = IngredientStock.objects.filter(ingredient=c.ingredient)
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total = 0
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for s in stock:
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total += s.amount
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if total < c.amount:
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raise UnableToPour("Not enough " + c.ingredient.name + " to pour drink!")
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port = serial.Serial(serialPort, 2400)
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if not port.isOpen():
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raise UnableToPour("Unable to open serial port!")
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for c in components:
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stock = IngredientStock.objects.filter(ingredient=c.ingredient)
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leftToPour = c.amount
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startTime = time.time()
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for s in stock:
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port.write(str(s.slot))
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if leftToPour < s.amount:
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time.sleep(secondsPerML[s.slot]*leftToPour)
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s.amount = s.amount - leftToPour
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s.save()
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break
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else:
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time.sleep(secondsPerML[s.slot]*(s.amount - ))
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leftToPour = leftToPour - s.amount - 30
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s.amount = 0
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s.save()
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print "Time to pour:" + str(time.time() - startTime)
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port.write("\n")
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port.close()
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Not exactly the most precise in terms of pouring accuracy, but it gets the job
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done as a prototype. As for the rest of the code, there's not too much else that's
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very interesting. I may release the code at some point in the future.
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