The One Scale

Dymo 10lb Scale

Other scales

That probably will work too

uint16_t scales[NSCALES][2] = {\
    // Stamps.com Model 510 5LB Scale
    {0x1446, 0x6a73},
    // USPS (Elane) PS311 "XM Elane Elane UParcel 30lb"
    {0x7b7c, 0x0100},
    // Stamps.com Stainless Steel 5 lb. Digital Scale
    {0x2474, 0x0550},
    // Stamps.com Stainless Steel 35 lb. Digital Scale
    {0x2474, 0x3550},
    // Mettler Toledo
    {0x0eb8, 0xf000},
    // SANFORD Dymo 10 lb USB Postal Scale
    {0x6096, 0x0158},
    // Fairbanks Scales SCB-R9000
    {0x0b67, 0x555e},
    // Dymo-CoStar Corp. M25 Digital Postal Scale
    {0x0922, 0x8004},
    // DYMO 1772057 Digital Postal Scale
    {0x0922, 0x8003}
};

https://github.com/erjiang/usbscale/blob/master/scales.h

Do I really need to Know C?

http://www.raywenderlich.com/wp-content/uploads/2014/01/pic2.png

Python to the Rescue

Python to the Rescue

from os import * # DON'T DO THIS

# Above import causes a name collision on "open"

with open("file.txt", "r") as f: 
    content = f.read()

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: an integer is required

C - Inspired Python

# Read 4 unsigned integers from USB device
hiddev_event_fmt = "IIII"
bytes_to_read = struct.calcsize(hiddev_event_fmt)
usb_binary_read = struct.unpack(hiddev_event_fmt, os.read(fd, bytes_to_read))

https://docs.python.org/2/library/struct.html

All Together

def getWeightInGrams(self, dev="/dev/usb/hiddev0"):
    grams = -1
    try:
        fd = os.open(dev, os.O_RDONLY)

        # Read 4 unsigned integers from USB device
        hiddev_event_fmt = "IIII"
        bytes_to_read = struct.calcsize(hiddev_event_fmt)
        usb_binary_read = struct.unpack(hiddev_event_fmt, os.read(fd, bytes_to_read))
        grams = usb_binary_read[3]
        os.close(fd)
    except OSError as e:
        print("{0} - Failed to read from USB device".format(datetime.utcnow()))
    return grams

Main Loop

def main(self):
   self._currentWeight = self.getWeightInGrams()

   while True:
       try:
           self._loopCount += 1
           tmpWeight = self.getWeightInGrams()

           if self.shouldLogWeight(tmpWeight):
               self._currentWeight = tmpWeight
               self.logToInitialState()
               self.writeToDynamo()

           if self.shouldPostToLed():
               self._loopCount = 0 
               self.postToLed()

           if self.potIsLifted():
               self._mostRecentLiftedTime = datetime.now()

       except Exception as e:
           self._logger.error(e)

       sleep(1)

Logging To Initial State

def logToInitialState(self):
   utcnow = datetime.utcnow()
   bucketKey = "{0} - coffee_scale_data".format(self.environment)

   streamer = Streamer(bucket_name="{0} - Coffee Scale Data".format(self.environment), 
           bucket_key=bucketKey, access_key=self.initialStateKey)

   if self.potIsLifted():
       streamer.log("Coffee Pot Lifted", True)
   streamer.log("Coffee Weight", self._currentWeight)
   streamer.close()

Initial State Dashboard

    Simple RESTful APIs Made Easy

• Combines AWS API Gateway with AWS Lambda (python, java, or nodejs)

• Approaching 1.0

• Hides complexity and implements deployment workflow

• Makes simple APIs very easy and inexpensive

Caveats

• Rich error handling is still difficult

• Framework is still a bit unstable as they head toward 1.0

• Code with compiled libraries can be tricky to build/deploy

• Enable API Gateway authentication!

Code

https://github.com/chalfant/serverless-coffee-scale

Python code using boto3 library to read/write records to DynamoDb

Curl To Get Entries

Coffee Graph

Display Hardware DIY

Andrew Kaczorek

It Begins With Hipchat

• The move to a room based chat system added a new social outlet
• Several Iterations of Chatbot
• How could we bridge our chat system into the real world?

    V1: Spark + (Tiny) OLED Fed by a Script Watching a Chat Room

Display: https://www.adafruit.com/products/931

Tiny Display Becomes Tiresome

• I2C implementation in Spark was Unreliable
• Integration with Spark Cloud required non-standard outgoing port

Time for Something Bigger

Display: https://www.adafruit.com/products/420

    Also, a Raspberry Pi Model B

• Allowed for running code other than Arduino-Compatible

• Multiple developers could easily contribute  

Wiring was Pretty Easy

Purchased ribbon cables for each end and patched the pinouts with breadboard wires

    Linux Wifi on the Pi Was Flaky

TESTIP=10.1.1.1

ping -c4 ${TESTIP} > /dev/null

if [ $? != 0 ]
then
    logger -t $0 "WiFi seems down, restarting"
    sudo /sbin/ifdown --force wlan0
    sleep 10
    sudo /sbin/ifup wlan0
fi

Run via cron every 5 minutes and call me in the morning

def render(mytext)
  draw=Magick::Draw.new {
    self.font_family = 'Comic Sans MS'
    self.fill="#6495ED"
    self.pointsize = 16
    self.font_weight = 600
    self.gravity = Magick::SouthWestGravity
    }
  metrics=draw.get_type_metrics(mytext)
  image=Magick::Image.new(metrics['width']+30,16) { 
    self.background_color = "black" 
    self.format = "PPM"
    self.depth = 8
    }
  draw.annotate(image,0,0,0,0,mytext) {
    self.font_family = 'Comic Sans MS'
    self.fill="#6495ED"
    self.pointsize = 16
    self.font_weight = 600
    self.gravity = Magick::SouthWestGravity
    }

How We Drive the Display

Ruby ->

• led-matrix -t 10 -D 1 runtext.ppm

• https://github.com/hzeller/rpi-rgb-led-matrix

C++ ->

    Adding the Ability for Multiple Data Feeds to the LED Panel

class Display
  extend Resque::Plugins::Logger

  @queue = :leddisplay

  def self.perform(localpath)
    logger.info "displaying #{localpath}"
    system("/root/ledsvc/led-matrix","-r16","-D1","-t30","#{localpath}")
    File.delete(localpath)
  rescue Resque::TermException
    logger.error "display #{localpath} failed"
    Resque.enqueue(self, localpath)
  end

end

Ruby Resque to the Rescue: https://github.com/resque/resque

Let's Monitor Just in Case

Process 'ledsvc'
  status                            Running
  monitoring status                 Monitored
  pid                               2247
  parent pid                        1
  uptime                            23d 0h 17m 
  children                          0
  memory kilobytes                  32776
  memory kilobytes total            32776
  memory percent                    7.3%
  memory percent total              7.3%
  cpu percent                       1.6%
  cpu percent total                 1.6%
  data collected                    Fri, 24 Jun 2016 13:23:31

I used monit: https://mmonit.com/monit/

    The Scale Project and LCD Matrix Project Come Together

• Initially, these ran on separate Pis
• Have been coexisting for the past ~14mo

    Future Plans for Display

• Display can be daisy-chained. Let’s do that.

• Variable time for message display

• Fixed-display statistics plus scrolling messages