Networking and Communications
Nov 29, 2016

The main goal for this session of the course is to learn about networks and communications. We are asked to design and build a wired &/or wireless network connecting at least two processors.

I wanted to try with a wireless module in order to be able to develop a phone app for my final project so I decided to use an ESP8266 from Adafruit.

I don't have a lot of experience in electronics so I decided to make a simple board with an LED that would turn on when sending a value from the phone. I think it is a good starting point if you don't have extended knowledge in electronics or microcontrollers. So I'll try to document it as good as possible:

Attiny44 with ESP8266 using Arduino IDE and Python

1. Design

I first designed the board in Eagle. The main idea is to connect the ESP8266 to the Attiny44 in order to send the information received via wifi to the microcontroller. Here's a couple of considerations for the design:

• We have to connect the TX pin from the ESP8266 to the RX pin of the Attiny44 in order to send the information we receive via wifi to the microcontroller.
• We have to connect the TX and RX pins from the ESP8266 to the FTDI connecting to the computer in order to be able to program the ESP8266 and get values from it to debug.
• We have to connect the TX and RX pins from the Attiny44 to the FTDI connection to the computer in order to be able to program the Attiny44 and get values from it to debug.
• We have to connect the output device (in this case, a Red LED) to one of the pins of the Attiny44.

The main problem of this design is that the TX and RX connections of the different modules can cause issues when trying to send data if the controllers are sending data at the same time. We will have to take this in account when programming.

Here's the list of the components needed:

• Attiny44 Microcontroller
• ESP8266 Wifi Module Adafruit
• Red LED [or whichever colour you fancy more]
• 1k Resistor [for LED]
• 10k Pull-up Resistor
• 1uF Capacitor
• Resonator
• Header 2x3 SMD
• FTDI Header x 2 [One for Usb serial and one for Wifi module]

This is the final design:

2. Milling and Stuffing the board

With the design ready, I milled the board. I had an issue when milling where one of the machines was milling too deep and I didn't manage to adjust the values so I had to change to the other Modela.

Once the board was ready I stuffed the board with all the components. I then added the ESP8266 and soldered it to the corresponding FTDI header. I also added a layer of black non-conductive tape to avoid having shorts on the bottom of the EPS8266.

3. Testing Attiny44

First thing to do when the board is ready is try to check the proper operation of the different parts separately.

I used the basic script for programming the Attiny44 that turned the LED on when sending a value over serial.

Here's the script on GITHUB: BLINK LED ATTINY44

Steps to program the Attiny44: [Just a little review]

• Connect FabISP to board.
• Connect FabISP to computer.
• Connect FTDI from board to computer via USB [to give power to board].
• Open terminal.
• Go to directory with your c file and make file. [you need the make file as well in order to compile the code]
• Type: make -f hello.ftdi.44.echo.c.make
• Type: make -f hello.ftdi.44.echo.c.make program-usbtiny-fuses
• Type: make -f hello.ftdi.44.echo.c.make program-usbtiny
• Use Neil's python script to check if connections are working.

4. Testing ESP8266 Wifi board

Once this is working, we will have to reprogram the Attiny44 in order to be able to program the ESP8266. We have to ensure that the Attiny is not sending any value over the TX pin. If the Attiny TX pin is set to output, the communication through that connection to the ESP8266 won't work. So now that you have ensured that the Attiny44 is working properly, follow next steps:

• Comment all code that sets the serial output on the Attiny c code.
• Load the code with the FabISP as indicated before.

Now we are ready to test the ESP8266. We will use the Arduino IDE to program the wifi board so we need to import the corresponding libraries in our Arduino IDE. Follow this instructions to install the ESP8266 board Package.

Here you can find a nice explanation on how to program your ESP8266 board to act as a web server:

ESP8266 Web Server with Arduino IDE

In this tutorial, there's an explanation on how to set your ESP8226 board to act as a webserver and turn on and off the two LED's on the board from a remote client. Main steps to follow are:

• Connect ESP8266 to your computer using the FTDI to USB.
• Select Board: Generic ESP8266 Module in your Arduino IDE Tools.
• Open the sample code from the tutorial.
• Change SSID and Password for your Wifi SSID and Password.
• Set your ESP8266 to bootload mode by holding down the GPIO0 button [the red LED will be lit] /While holding down GPIO0, click the RESET button, Release RESET, then release GPIO0 When you release the RESET button, the red LED will be lit dimly, this means its ready to bootload.
• Compile and Load from Arduino IDE.

Once the board is programmed, open the serial terminal in the Arduino IDE. The board should be trying to connect to the wifi network you especified and you should see the IP address that has been assigned to it.

If you open the browser from another device (laptop, phone, etc) and type the IP address followed by the arguments of the script (for example: http://10.189.52.226/socket1On), you should be able to see a webpage with 4 buttons that let you turn on and off the LED from the ESP8266 board.

5. Integrating

Once the wifi board is working, adjust the code in the Arduino IDE to send values to the Attiny44. In our case, we want the wifi module to send an 'r' everytime we press the button. so we will use:

Serial.print('r');

This will send an 'r' character to the Attiny44 everytime we press the button on the website.

Update the code on the ESP8266 by putting it into boadload mode and comp&load from Arduino IDE.

Now you just need to upload the initial code for the Attiny44 [remember we commented first to avoid having issues with the communications?]. So basically:

• Uncomment blink LED code from c file.
• Connect FabISP to board.
• Connect FabISP to computer.
• Connect FTDI from board to computer via USB [to give power to board].
• Open terminal.
• Go to directory with your c file and make file. [you need the make file as well in order to compile the code]
• Type: make -f BlinkLED.c.make
• Type: make -f BlinkLED.c.make program-usbtiny-fuses
• Type: make -f BlinkLED.c.make program-usbtiny

And that's it!!! If you open a browser and go to the EPS8266 web server address you should see the button and when you press it, the LED on the Attiny44 should turn on.