Read a USB scale with RaspBerryPi store the data in a database and display coffee status.

Thanks to : http://steventsnyder.com/reading-a-dymo-usb-scale-using-python/ for providing the starting point and the scale reading code

• packages

sudo apt-get update
sudo apt-get upgrade
sudo apt-get -y remove festival apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common libapache2-mod-php5
sudo apt-get -y install mpg123  php5-sqlite man espeak sqlite3 subversion git openssh-server ntp lighttpd libusb-1.0 mysql-server python python-mysqldb php5 php5-mysql phpmyadmin python-setuptools python-pip python-dateutil ssmtp mailutils
sudo apt-get install python-qt4
sudo apt-get install xvfb
sudo pip install twython

seems to REQUIRE an older version of pyusb on newer linux
sudo pip install pyusb==1.0.0b1

sudo pip install shutil

• PYUSB -- used for python to access the USB devices installed above to specific older version based on information from this page: https://github.com/arvydas/blinkstick-python/wiki/NotImplementedError-is_kernel_driver_active-on-some-Linux-systems

sqlite3 c16

CREATE TABLE 'settings' ('id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 'setting_name' REAL NOT NULL, 'setting_value' REAL NOT NULL);
CREATE TABLE 'readings' (
  'reading_time' datetime NOT NULL,
  'reading_value' INTEGER NOT NULL,
  'scale_id' INTEGER NOT NULL,
  'id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
  'reading_units' varchar(10) NOT NULL);
CREATE TABLE 'scales' (
  'id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,'scale_name' TEXT NOT NULL,'vendor_id' TEXT NOT NULL,'product_id' TEXT NOT NULL,'serialno' TEXT NOT NULL,'data_mode_grams' INTEGER NOT NULL,'data_mode_ounces' INTEGER NOT NULL
  );
CREATE TABLE 'tweets' ('tweet_time' INTEGER NOT NULL, 'message' INTEGER NOT NULL, 'type' INTEGER NOT NULL default 'update', 'scale_id' INTEGER);
CREATE TABLE 'texts' (
  'sms_time' datetime NOT NULL,
  'msg' TEXT NOT NULL,
  'type' INTEGER NOT NULL,
  'scale_id' INTEGER NOT NULL,
  'id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
  'recipient' TEXT NOT NULL);

run dmesg to see if it is connected. the output should be almost exactly like this:

[61539.300131] usb 1-1.2.1.4: new full-speed USB device number 6 using dwc_otg
[61539.405516] usb 1-1.2.1.4: New USB device found, idVendor=0922, idProduct=8004
[61539.405548] usb 1-1.2.1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[61539.405568] usb 1-1.2.1.4: Product: M25 25 lb Digital Postal Scale
[61539.405584] usb 1-1.2.1.4: Manufacturer: DYMO
[61539.405596] usb 1-1.2.1.4: SerialNumber: 0000000022159
[61539.437452] generic-usb 0003:0922:8004.0001: hiddev0: USB HID v1.01 Device [DYMO M25 25 lb Digital Postal Scale] on usb-bcm2708_usb-1.2.1.4/input0

bash script to extract the vendor id and product id (would be nice to use python to parse dmesg to grab the stuffs but that may not be feasible) in fact this may not be necessary as the scale id's are always the same...

# this gets just the vendor id
dmesg | grep -B6 DYMO | grep idVendor | cut -d"=" -f2 | cut -d"," -f1
# this gets just the Product id
dmesg | grep -B6 DYMO | grep idProduct | cut -d"=" -f3

it should tell you how many scales are connected, and whether or not they exist in the database. If they don't exist, this will add them

root@c16:/usr/local/CoffeeScale# ./getscaleinfo.py
There are 2 scales connected!
scale #1
0000000022159
DYMO
M25 25 lb Digital Postal Scale
row:1
serial 0000000022159 already exists in database
scale #2
0000000038053
DYMO
M25 25 lb Digital Postal Scale
row:1
serial 0000000038053 already exists in database

add psmonitor.sh to the crontab - this will watch for the running monitorScale.py application and restart it if necessary.

* * * * * /usr/local/CoffeeScale/psmonitor.sh

caused by udev permissions:

python /usr/local/CoffeeScale/readscale.py
usb.core.USBError: [Errno 13] Access denied (insufficient permissions)

• the fix:

sudo vi /etc/udev/rules.d/98-dymo.rules
$ sudo cat /etc/udev/rules.d/98-dymo.rules
SUBSYSTEM=="usb", ATTR{idVendor}=="0922", ATTR{idProduct}=="8004", MODE="666"

what if you have more than one scale? according to pyusb documentation, usb devices sometimes have "bus" and "address" identifiers

devices = usb.core.find(find_all=True, idVendor=VENDOR_ID, idProduct=PRODUCT_ID)
sys.stdout.write('There are ' + str(len(devices)) + ' scales connected!\n')
if len(devices) > 1:
	print "more than one scale found"
else:
	print "devices bus: " + str(devices[0].bus)
	print "device address: " + str(devices[0].address)

they also show serial numbers and here is how to get them

devices = usb.core.find(find_all=True, idVendor=VENDOR_ID)
sys.stdout.write('There are ' + str(len(devices)) + ' scales connected!\n')
scales=[]
i=1
for device in devices:
	scalename="scale "+str(i)
	print "scale #" + str(i)
	devbus = str(device.bus)
	devaddr = str(device.address)
	productid=str(device.idProduct)
# help found here http://stackoverflow.com/questions/5943847/get-string-descriptor-using-pyusb-usb-util-get-string
	serialno = str(usb.util.get_string(device,256,3))
	manufacturer = str(usb.util.get_string(device,256,1))
	description = str(usb.util.get_string(device,256,2))

read the scale should output just one number: the weight in grams

• core of the system - runs constantly to read the scale(s) and determine if the reading changed
• if the reading changes, send the new reading (time stamped) to the database via the script sendReading.py

• imported into monitorScale.py via an include
• sole purpose is to send a reading into the database and timestamp it. monitorScale.py sends the scale id and the weight values to this script for saving.

• this script's sole purpose is to get the serial number and metadata from the scales and insert it into the database.
• it is the initial framework for part of the admin system

• this is the initial web display. Currently uses javascript to query the script 'scaleReport.py'

function getStatus() { 
    $('div#status').load('/cgi-bin/scaleReport.py');
    setTimeout("getStatus()",500); 
}

• this scripts only job is to report the latest scale reading so the web page can grab it
• queries the database to determine how many scales exist in the database and creates <div> sections for each one

• Configure lighttpd:

- sudo nano /etc/lighttpd/lighttpd.conf
- Change Document Root and, optionally, port
- Add the following line to the 'server.modules' section:
  "mod_cgi",
- Then to get lighttpd to recognze python scripts we need to add the following new section at the end of the file.

$HTTP["url"] =~ "^/cgi-bin/" {
    cgi.assign = (".py" => "/usr/bin/python")
}

- Now restart Lighttpd:
- sudo /etc/init.d/lighttpd restart

Create the folder /usr/local/CoffeeScale/cgi-bin and set permissions:

# mkdir /usr/local/CoffeeScale/cgi-bin
# sudo chown www-data:www-data /usr/local/CoffeeScale/cgi-bin

• do the setup steps above (probably have to make the scripts executable)
• put index.php in your web server document root
• put sendReading in the web server's cgi-bin folder (or change the code in index.php to point to the correct place)
• run getscaleinfo.py which will populate the scales table
• run monitorScale.py which will send readings into the readings table
• load index.php in a web browser

• not run as root!
• triggered events
• watch for and react to events such as
• newly filled coffee pot
• empty pot
• draw from pumper
• interact with web services
• twitter
• facebook
• email
• sms
• admin backend
• ability to add and remove scales interactively
• monitor alerts
• reports on coffee consumption/activity
• administer users
• users
• add user interface where users can sign up to receive alerts.
• web display
• more interactivity

update 02/8/2013 the SD card died so I have a new SD card and am glad I checked the code in I am trying "mobiuslinux" for the distro this time: http://moebiuslinux.sourceforge.net/ it is smaller and has no graphical stuff. I may come to need graphical stuff but for now just the basics will hopefully make a faster updating thinger