A Simple Interface for the Internet of Things with my Raspberry Pi

A Simple Interface for the Internet of Things

Awhile back I bought the Adafruit starter kit for the LPC810.

LPC811  on a TSSOP-16 breakout board

With much trial and error I was able to get a simple serial communication with it through a ttl usb cable.  I then wanted to control the I/O remotely. This device can be polled for status and controlled through tcp messages from your Android/iOS device and Raspberry Pi

My Remote Control portable plug
Parts:

• 1 - LPC810
• 1 - HLK-RM04
• 1 - ULN2803APG
• 3 - 1k ohm Resistors
• 1 - 120v to 5v 500mA converter module (ebay)
• 1 - 2Ch relay module
• 1 - prototyping board

and connected it all up:

simple code for controlling my plugs in python:

import socket
class PlugPoller(threading.Thread):
 def __init__(self,ip,port):
  threading.Thread.__init__(self)
  self.ip=ip
  self.port=port
  self.connect(ip,port)
  self.status='0000'
  self.command='!getstat\r'
 def connect(self,ip,port):
  try:
   self.s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
   self.s.settimeout(1)
   self.s.connect((ip,port))
  except:
   pass
 def run(self):
  while True:
   try:
    sleep(.1)
    self.s.send(self.command)
    self.status=str(self.s.recv(4))
    #print "data:{"+self.command,self.status+"}"
   except:
    print 'error'
    sleep(5.0)
    self.connect(self.ip,self.port)
    pass
   if(self.command!='!getstat\r'):
    #print self.command
    self.command='!getstat\r'
 def getstatus(self):
  return self.status
 def sendcmd(self,c):
  try:
   self.s.send(c)
  except:
   pass
  return self.s.recv(4)
def main():
 plug=PlugPoller("192.168.16.254",8080)
 plug.start()#start the async status poller
 plug.sendcmd('!turnon1') #turns on relay 1
 plug.sendcmd('!trnoff1') #turns off relay 1
 plug.getstatus() #returns a status of 0001, first two binary numbers are the button inputs the last two are the relays
 plug.sendcmd('!talloff')#turns off all relays

Whenever these inputs are pressed it will toggle the relays locally. The pushbuttons  would be connected to the right side of the Wifi Module.   Giving you remote and local control of your device without having to put an Arduino or Raspberry Pi in that enclosure.
For me I like knowing instantly whether my light is on while looking at it remotely. The PlugPoller python script is polling statuses every tenth of a second.  The MCU and the module talk at 115k baud so you can get your results pretty quickly.

Since that looked pretty ugly (prototype), i'm currently working with the LPC811 which has more I/O.  14 configurable pins, 2 of which I will use for UART communication (12 for I/O pins) which will let you sense more inputs and turn on more outputs.  These chips can have some of these pins configured for i2c and spi that can connect you to 100s of sensors that you can have through wifi.


Please Comment if you wish to see this as a kit you could buy
Or if you have questions

Raspberry Pi SCADA Part 2, Modbus TCP PWM Controller

Raspberr Pi SCADA Part 2, Modbus PWM Controller

Since finding a cheap alternative to PLC whilst using an industrial protocol is a popular idea the Raspberry Pi has caught many eyes on doing this.  I posted once on reading a temperature sensor and serving it up on the Pi using ModbusTCP. This time I expound on it and show you how to control something. In this case it will be a PC 12v fan.

Parts:

• 1 x Raspberry pi
• 1 x Darlington Transistor
• 1 x PC Fan (with about  500ma load)
• 1 x 12v DC Power Supply

Setup:

1. Installing pymodbus and dependencies:
• sudo apt-get install python-pymodbus python-twisted-conch
2. Wire up your Fan, LED, or motor
   
   
   
   

1. View my code from Github.

Video of what I did:

Source Code:

from pymodbus.server.async import StartTcpServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSequentialDataBlock, ModbusSlaveContext, ModbusServerContext
from pymodbus.transaction import ModbusRtuFramer, ModbusAsciiFramer
from twisted.internet.task import LoopingCall
from threading import Thread
import pid
import threading
from time import sleep
import RPi.GPIO as GPIO
import os
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')
#set up Raspberry GPIO 
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(25,GPIO.OUT)
pwm = GPIO.PWM(25,60)
pwmDutyCycle=100
pwm.start(pwmDutyCycle)
temperaturePoll = None

class Temp(Thread):
    """
     A class for getting the current temp of a DS18B20
    """
    def __init__(self, fileName=''):
        Thread.__init__(self)
        super(Temp, self).__init__()
        self._stop = threading.Event()
        self.tempDir = '/sys/bus/w1/devices/'
        list = os.listdir(self.tempDir)
        if(list[0][:2]=="28"):
         fileName=list[0]
        self.fileName = fileName
        self.currentTemp = -999
        self.correctionFactor = 1;
        self.enabled = True
        self.Run=True
    def run(self):
        while self.isEnabled():
   try:
    f = open(self.tempDir + self.fileName + "/w1_slave", 'r')
   except IOError as e:
    print "Error: File " + self.tempDir + self.fileName + "/w1_slave" + " does not exits"
    return;
   lines=f.readlines()
   crcLine=lines[0]
   tempLine=lines[1]
   result_list = tempLine.split("=")
   temp = float(result_list[-1])/1000 # temp in Celcius
   temp = temp + self.correctionFactor # correction factor
   #if you want to convert to Celcius, comment this line
   temp = (9.0/5.0)*temp + 32
   if crcLine.find("NO") > -1:
    temp = -999
   self.currentTemp = temp
   #print "Current: " + str(self.currentTemp) + " " + str(self.fileName)
   sleep(.5)
    #returns the current temp for the probe
    def getCurrentTemp(self):
        return self.currentTemp
    #setter to enable this probe
    def setEnabled(self, enabled):
        self.enabled = enabled
    #getter
    def isEnabled(self):
        return self.enabled


def updating_writer(a):
 context  = a[0]
 register = 3
 slave_id = 0x00
 address  = 0x00
 global pwmDutyCycle,temp
 #uncomment to debug temperature
 print temp.getCurrentTemp()
 values = [int(pwmDutyCycle),temp.getCurrentTemp()*100]
 context[slave_id].setValues(register,address,values)
def read_context(a):
 context  = a[0]
 register = 3
 slave_id = 0x00
 address  = 0x00
 value = context[slave_id].getValues(register,address)[0]
 global pwmDutyCycle
 if(value!=pwmDutyCycle):
  print value
  pwmDutyCycle=value
  pwm.ChangeDutyCycle(pwmDutyCycle)
def main():

 store = ModbusSlaveContext(
  di = ModbusSequentialDataBlock(0, [0]*100),
  co = ModbusSequentialDataBlock(0, [0]*100),
  hr = ModbusSequentialDataBlock(0, [0]*100),
  ir = ModbusSequentialDataBlock(0, [0]*100))
 context = ModbusServerContext(slaves=store, single=True)
 identity = ModbusDeviceIdentification()
 identity.VendorName  = 'pymodbus'
 identity.ProductCode = 'PM'
 identity.VendorUrl   = 'http://github.com/simplyautomationized'
 identity.ProductName = 'pymodbus Server'
 identity.ModelName   = 'pymodbus Server'
 identity.MajorMinorRevision = '1.0'
 time = 5 # 5 seconds delaytime = 5 # 5 seconds delay
 writer = LoopingCall(read_context,a=(context,))
 loop = LoopingCall(updating_writer, a=(context,))
 loop.start(.5) # initially delay by time
 writer.start(.1)
 StartTcpServer(context, identity=identity)#, address=("localhost", 502))
 #cleanup async tasks
 temp.setEnabled(False)
 loop.stop()
 writer.stop()
 GPIO.cleanup()
if __name__ == "__main__":
 temp = Temp()
 temp.start()
 main()

Home Automation Project #4 1-Wire I/O Performance Test

Dallas has a couple 1-Wire I/O chips out there.  I decided to test the one that seemed practical to replace a light switch or plug. The DS2413 was almost perfect.  It has 2 I/O, gets power from the data line, and Adafruit made it easy for me to test by making the breakout board.

Here's what I used for my test:

• Adafruit  DS2413 Breakout board.  
• RPI3 I2C to 1-Wire Host Adapter with 8 1-wire bus lines. (Sheepwalkelectronics has other RPi addon boards that put the 1-Wire it to a RJ-45 jack and provided power through the data line.)
• OWFS Python Library. Instructions on compiling it here 
• owpython

With these I created a demo to see the read and write speeds through the 1-wire data line.
Source code for benchmark:

As you can see the performance dropped more than half every time I pressed the button.  Not bad if all I care about is whether the light turns on right when I press the button, and it would.
I then ran the loop to see how fast it would go at turning on and off the relay and saw an average of 20.833 requests per second. (Don't worry, the relay wasn't able to click on and off that fast)

Adding a DS18B20 Temperature sensor and requesting it every second I found that when the temperature was requested the requests per second dropped down to 1.950 requests per second and then jumped back up to the 42.27 range until the next second came along.

Requesting the temperature every loop cycle was unworkable.  I had to hold my finger on the button far longer than desired to get the relay to turn on.  I tuned it up by requesting the lesser accurate temperature value "fasttemp".  I also requested it less often (every other second).

t=ow.Sensor('/28.B0A534050000')
t.useCache(False)
print t.fasttemp

The DS2413 datasheet mentions the ability for Overdrive (~10x the communication speed) but I was unsuccessful on getting it to work.  The communication would seize when I tried enabling it on the bus.

Conclusion:
Controlling your lights with the DS2413 is possible, but you are limited on the quantity of chips on the same bus line. If you are able to get the chip's Overdrive feature working then I would suggest getting the 8-port i2c to 1-wire add-on board if you have plans for your whole house.

I'm going to test the DS2408 (8 port 1-Wire I/O chip) soon and am a little more hopeful since you can control multiple rooms and/or lights with one chip.

(Pictures coming soon.)