Home Automation Server With Router




Introduction: Home Automation Server With Router

Turn a cheap router into a home automation server!

This project will allow you to switch outlets/lights from your iPhone, or any browser.
You will also be able to send out serial commands remotely.

This project is based on SmartLinc.

• OpenWRT compatible router, with serial header
• AVR microcontroller Development Board (like Arduino)
• Actuators like: RF switched outlets (433.92Mhz) with a remote

Step 1: Overview

The System
The Router runs a web server, you access it via browser.
After you push a button on the web page the router sends out a serial command,
 we process this with a microcontroller, the AVR converts it to RF protocol, injects it into the RF remote, which controls the RF outlets.

Step 2:

Buy a router, listed here:http://wiki.openwrt.org/toh/start

I chose the TP-Link TL-WR741ND, because it is cheap (~$30).

Disassembly it (this will void the warranty!). You will have to solder a serial header to the circuit board, to gain access to the serial port.
The TL-WR741ND instructions can be found here: http://wiki.openwrt.org/toh/tp-link/tl-wr741nd
For other routers, search here: http://wiki.openwrt.org/toh/start

After finished soldering, manage the four cables out of the case, through the vent holes. I used a RJ22 plug at the end, for rapid connection.

Step 3: Configure the Router

Install the Linux based OpenWRT firmware on the router.
The TL-WR741ND instructions can be found here:

 If you are stuck, start here: http://openwrt.org

After you have a working SSH connection you can proceed.

Because of the router (by default) runs the web admin page on the port 80, we need to add a secondary port to serve our custom web site. For that, we need to configure the uhttpd (web server application) configuration file.

Download WinSCP, to simply do this through SSH.

Set up a new connection:
Host name: normally (by default)
Port: 22
User name: root
Password: what you gave after installation
File protocol: SCP

Find this file: /etc/config/uhttpd

Copy the following into it:

config 'uhttpd' 'secondary'
option 'listen_http' '81'
option 'home' '/HomeAutomation/www'
option 'cgi_prefix' '/cgi-bin'
option 'script_timeout' '60'
option 'network_timeout' '30'

And save it.

Step 4: Setup the Web Page

Upload the /HomeAutomation/ folder structure into the root directory.

Set permissions for the script files located here:
 Select all of them -> F9 Properties -> set the execution rights (X) for everyone (Owner, Group, Others)

Close WinSCP, restart router (e.g. recycle power).
 Now the web server is ready. Try it out:
 Open up a web browser, type in:
 You should see your custom web page.

If you press a button on the included web page, the router will send out serial commands through the previously attached serial cable.

 We need to intercept these commands and process them. For that purpose we need to build a microcontroller board (like Arduino).

The included web site is very basic. If you make good CGI/AJAX based web sites please share it with us.

How does the web site work
  When you click on a button, the browser loads a script file, the router executes the shell commands (serial outputs) located in each cgi file. The script file then redirects the browser back to the index page (takes about ~1sec).

 If you want to output custom serial commands, modify the .cgi files.
Serial commands are sent out like this:

echo -e "\x9B\x11\x08\x22\xC5\x0D" > /dev/ttyS0
 (the \x modifier is used to output data in HEX instead of ASCII)

Protocol detail
I made this simple as possible. One package contains:

 Byte#    Function:
 1.        Synchronization (0x9B)
 2.        Message type, use 0x00 or 0x01 for now (check firmware for details)
 3.        Data1
 4.        Data2
 5.        Checksum (calculated from Byte#2-4)
 6.        End character (, 0x0D)

Step 5: Hardware

For me the Atmega88 (with internal 8Mhz oscillator) failed to run on 3V3 (supplied by the router), so I had to include an external power supply, with 5V.

 Because of that, we need to make a voltage conversion between the
5V MCU <-> 3V3 Router serial.
This PSU also has a 12V rail for the RF remote control, so it can run without battery.

Signal injection into RF remote controller
You need to find your own remote control's data path, normally it is between the IC and the transistor (see image). Use a resistor for driving the transistor.

Burn the firmware using:



Oscillator: internal 8Mhz
Clear DIV8 fuse!
Firmware included in zip file. You are more than welcome to share your improvements on the software.

Step 6: More Technical Details

Commonly used ICs in the RF switched outlet and remote controls are:
Remote Decoder PT2272.pdf
Remote Encoder HX2262.pdf
The RF protocol is included in these datasheets.

The reaction time from pressing a button on the page to the serial output from the router is:
iPhone & wifi: 1sec
 PC & LAN: instantaneous (~100mS)
The delay can be decreased by using an AJAX based web page .

Step 7: What Is Gained?

• You get a linux based system, running your custom softwares 24/7 with a power consumption of only 4.5W.

• Connect an IP webcam, embed the video feed in web page

• Ability to send out custom serial commands to any external device.
(be aware of the 3V3 serial voltage levels, I would strongly advise you to use CD40106 as a buffer)

• In this application you are able to send out any possible RF commands (based on the RF protocol) to the receivers. (i.e. no limitations on button numbers on the remote control)

How stable is it?
The system will not miss any commands, thanks to the TCP/IP Internet protocol and to the sophisticated microcontroller firmware.

Further improvements:
Tap into the switched outlet's RF receiver, add a MCU, detect data pattern, output IR code and you will get an Internet based remote controlled, remote control :D

Write software for the router that can handle incoming serial data.
YES you will be able to Twitt from your router (e.g. power consumption reports from external measuring devices).
Or do old school things like SMS two way control, home alarm system, IR repeater (through web), scheduler program to automatically control things on time bases.

Here is the original SmartLinc web page (it uses AJAX, and runs on AVR web server!)
This is a good way to start developing web pages.

 Don't forget to share what have you done with this project.

Created by:
Arpad Toth
All rights reserved
Some pictures are taken from other sites, I do not own all of it.
Thanks for reading.

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10 years ago on Introduction

Check out my latest project:


8 years ago

I can program Ajax based web sites. Plus I'm also a HTML5 mobile User Experience designer & programmer. I'm going to do the project and come up with a cool app like web page. Keep you posted!


Reply 8 years ago on Introduction

Sounds great!
Here is one companies webpage collection running on embedded server (like linux routers), I think it uses ajax. It can be reused.
Need to keep it small and fast, because it runs on ~200Mhz.


10 years ago on Introduction

Great project!
I am doing it, but I have a problem that hex data is not received correctly.
First I tried to send from the router to my PC via:

echo -e "\x9B\x11\x08\x22\xC5\x0D" > /dev/ttyS0

I received: 0x9B 0x11 0x08 0x22 0xC5 0x0D 0x0D 0x0A
I receive 2 bytes in excess and I don't know why!

Then I tried to send from the router to pic, then from pic to my PC to check the received data, I get only 6 bytes but all wrong, not the data I sent.

I am using pic18f452 as I didn't use avr before..
I think the problem is the interface circuit..I used shmitt trigger, res, cap as you did but it doesn't work. Is this circuit need to be modified to be suitable for PIC?


Reply 10 years ago on Introduction


I also had some hard time with the router's serial port, because it uses weird voltage levels like ~1.8V in idle.
I pulled up the TX line (from the router) to 3V3 (from Vdivider+Cap), you should fed this into two inverters (powered from 3v3). Measure this output in idle state, it should read 3-3,3V.

3V3 TX line should be enough for any kind of 5V MCUs.

For proper communication with the PC you need 3V3 TTL - RS232 converter,
for 5V converters you could use a second voltage shifter on the TX line.
And always use pull ups on the inputs. I'm guessing you got those extra bytes because of noise (generated by weak or omitted pull ups or low voltage levels on the converter). An oscilloscope would be very handy in these situations.

You can debug your PIC's FW by sending out the data from the PC to PIC. The baud is 115200 8N1

I can recommend this adapter, it works on 3V3 and 5V at any speed:


Reply 10 years ago on Introduction

Thank you very much. The inverter solved the problem =)
I used the same cct in your schematic, but replaced smhitt trigger with 2 inverters
For excess bytes, it was CR & LF characters. echo -n solved this.
But when I send data from the PIC to the Router, How can I receive the data in index page for example?


Reply 10 years ago on Introduction

Sorry, I forgot that I used commands like this:
echo -e -n "\x9B\x21\x01\x21\xBD\x0D" > /dev/ttyS0

I haven't done any two way communications yet.
But it should work like on a desktop PC:


Check out the Cron scheduling service on the router, it can run commands on timely bases. Or run scripts like this:
run every 4min:
if ping google fails -> reset modem's switchable socket.

Or turn on sprinkler/Christmas lights at a given time.


Reply 10 years ago on Introduction

Really appreciate your help..I have successful two way communications :)

I have inquiry about ADSL Modem and the Router connection. I have modem & router in one device TD-W8901G with default ip and router wr741nd default ip
I must connect cable from router to my PC to be able to acess
Can I access this page without the need for the cable? My PC is connected to the internet via wireless from TD-W8901G, in another words,, when I type in my browser, the ADSL modem forward to the port where the router is connected to.
Also I want the web page be public over the internet.
Same manner,The ADSL has real ip, for example I want when some one enter in his browser, my ADSL modem forward this to the port where the router is connected to, then the router forward to port 81, web page.
Is there a tutorial about how to do that?
Hope my question is clear enough! :)


Reply 10 years ago on Introduction

Can you describe the serial reception, or attach the program?
For network setup refer to the image.


Reply 10 years ago on Introduction

Thank you for your help mrx23dot :)
For serial reception, I used only voltage divider at Rx of the router to make 5v --> 3.3v
And used command cat for reception, default baud rate 115200. I tried to send ASCII characters and received successfully. When I finish reception of HEX Data, I will attach the full program.


Reply 8 years ago on Introduction

hey can you post the full program you used? I still can't receive anything with RX pin on the router :(
would be much appreciated, thank you for your time :)


Reply 8 years ago on Introduction

- It is better to us Micro-controller that operates on 3.3v (like PIC18F452), so you will connect the Router and Controller directly without any additional circuits between them,i.e..Connect Router Tx pin to Controller Rx pin and vice versa.
- By default the serial port of the router is occupied by the console. So it can’t be used for other uses. To free the serial port: open /etc/inittab and remove the last line of the serial port ttyS0:
ttyS0::askfirst:/bin/ash --login
- To send/receive you should config the serial port first on the router:
stty -F /dev/ttyS0 115200 cread cs8 -parenb -cstopb sane -echo -echok -icrnl -ixon -icanon -opost -onlcr time 1 min 0
- To send data from router to controller: echo -e -n "\x9B\xA1\x02\xA3\x0D" > /dev/ttyS0
- To receive data: x="$(cat /dev/ttyS0)"

Hope this help! :)


Reply 8 years ago on Introduction

Thanks alot alot alot, seriously thanks,
Really appreciate it. :)


Reply 10 years ago on Introduction

Hello Sir,
I am still confused with this setup. May you clear the steps please?
How to enable DHCP client?
How to get router's mac address?


Reply 10 years ago on Introduction

For all your questions here is the documentation:


Reply 10 years ago on Introduction

Hello mrx23dot,

This is what I did for serial reception

First, I used voltage supply 3.3v to my PIC18F452 instead of 5v, and then connected the PIC and the Router directly without the need for inverters, shmitt trigger, ... etc

For reception to the router:
The firmware needs to be upgraded to add packages: coreutils, setserial, using commands opkg install/update

Then to receive data I used:

stty -F /dev/ttyS0 115200 cs8 -parenb ....
#there are many parmaeters to be set according devices specs

cat /dev/ttyS0 >> a.txt
#read data and save it a.txt file

setserial -a /dev/ttyS0 >> is used to check that the device is configured properly


8 years ago on Step 3

Hey I have the newer version of the router and i was trying to find the Find this file: /etc/config/uhttpd in the latest version i installed from the wrp website but i couldnt find it. Any ideas on where else to look for that?


9 years ago on Introduction

hello, i would really appreciate it if you could send me the arduino code. i have seen a link where you posted this before (2012) its a zip file and i dont understand its contents. what are all those files and where is the actual arduino code. thanks