Embedded Communication

Embedded communication is the process of sending information between two MCUs or from one circuit to other. For a communication to happen there needs to be a transmitter and a receiver. Communication may be in one direction or in both directions, there are different classifications according to this, but the basic classification is Synchronous and Asynchronous communication.

Synchronous: means sender and receiver use the same clock signal. Asynchronous: means sender provides a synchronization signal to the receiver before starting the transfer of each message.

There are two types of communication protocols which are classified below:

1. Inter System Protocol

2.Intra System Protocol

1.Inter System Protocol: The inter system protocol using to communicate the two different devices. Like communication between computer to microcontroller kit. The communication is done through a inter bus system.

Different categories of Inter system protocol:

UART Protocol

UART stands for universal asynchronous transmitter and receiver .UART Protocols is a serial communication with two wired protocol .The data cable signal lines are labeled as Rx and Tx. Serial communication is commonly used for transmitting and receiving the signal. It is transfer and receives the data serially bit by bit without class pulses. Ex: Emails, SMS, Walkie-talkie.

USART Protocol

USART stands for universal synchronous and asynchronous transmitter and receiver. It is a serial communication of two wire protocol. The data cable signal lines are labeled as Rx and TX. This protocol is used to transmitting and receiving the data byte by byte along with the clock pulses. It is a full-duplex protocol means transmitting and receiving data simultaneously to different board rates. Different devices communicate with microcontroller to this protocol.

Ex:-Telecommunications.

USB Protocol

USB stands for universal serial bus. Again it is a serial communication of two wire protocol. The data cable signal lines are labeled D+ and D-.This protocol is used to communicate with the system peripherals.USB protocol is used to send and receive the data serially to the host and peripheral devices.USB communication requires a driver software which is based on the functionality of the system.USB device can transfer data on the bus without any request on the host computer.

Ex: Mouse, Keyboard, Hubs, switches, pen drive.

2.Intra System Protocol: The Intra system protocol is used to communicate the two devices within the circuit board. While using this intra system protocols, with out going to intra system protocols we will expand the peripherals of the microcontroller. The circuit complexity and power consumption will be increases by using intra system protocol. Using intra system protocols circuit complexity and power consumption, cost is decrease and it is very secure to accessing the data.

Different categories of Inter system protocol

I2C Protocol

I2C stands for inter integrated circuit. I2C requires only two wires connecting all peripherals to microcontroller.I2C requires two wires SDA (serial data line) and SCL (serial clock line) to carry information between devices. It is a master to slave communication protocol. Each slave has a unique address. Master device sends the address of the target slave device and read/write flag. The address is match any slave device that device is ON, remaining slave devices are disable mode. Once the address is match communication proceed between master and that slave device and transmitting and receiving the data.

SPI Protocol

SPI stands for serial peripheral interface. It is one of the serial communication protocol developed by Motorola. Some times SPI protocol is also called a 4-wire protocol. It requires four wires MOSI, MISO, SS, and SCLK.SPI protocol used to communicate the master and slave devices. The master first configures the clock using a frequency. The master then selects the particular slave device for communication by pulling the chip select button. That particular device is selected and starts the communication between master and that particular slave. The master select only one slave at a time. It is full duplex communication protocol. Not limited to 8 bit words in the case of bit transferring.

CAN Protocol

CAN stands for controller area network .It is a serial communication protocol. It require two wires CAN High (H+) and CAN low (H-).  It was developed by the Robert bosh company in 1985 for in vehicle networks. It is based on a message oriented transmission protocol.

Making an App

There are several different ways to make an android app these days. As days progress, makers have `come up with simpler solutions to create apps. As I am new to programming and have almost had zero knowledge I had to use a method that involved less coding, and the only viable option for that, which I knew of was MIT app inventor. But then I googled in the attempt to find out any other software that offers the same. That's when I came across Thunkable. Thunkable runs on MIT app inventor. It is the same as MIT app inventor because the makers of thunkable belonged to the team that made MIT app, they broke off to make their own platform.

The software works exactly the same as MIT app but the there certain (minor) differences between the two, like the user interface, some features etc making the Thunkable app slightly better. I went on to use Thunkable for my purpose and the tutorials for thunkable is also great.

The tutorials are split as beginners, intermediate and advanced depending on the user's knowledge and capabilities. I started with the beginner tutorials to get the hang of the software and its UI. It was pretty simple to understand and proceed on.

1. Choosing platform for the app

2. A Gmail account is a must to use this app

3. The next step is to create the app itself

Once the app opens up this is the screen that you are greeted with.

To explain the user interface of the app,(Refer image above)

1.The palette:

This is where all the blocks are. The blocks are categorized into their functions like user interface, connectivity, sensors. Etc. To use them one has to simply drag and drop onto the screen.

2.Screen.

This is an imitation of the phone screen itself. All user interface blocks that are placed here is what will make the app. The look of the app has to be arranged here.

3.Components

All the blocks that are used in the making of the app are displayed here in the component section. If they are nested, that also is displayed here.

4.Properties.

The properties of each block can be controlled from here. The controls include color, size, orientation, images etc.

5.Menu bar

Here the app menu provides an option with, saving the app, creating a new app etc while the test menu provides real-time testing options. The export option is to export the app as apk or provide a QR code that helps to download the app. The help sections are linked to the docs.

6.UI and Programming

This bar helps to shift between designing the app and working of the app. The blocks shifts to a new window where the functioning of the app is configured.

 This is the comparison between the UI of MIT app inventor and thubkable. I found thunkable to be cleaner.

So now to actually make the app.

First I wanted to change the color of the main screen. This I did with the option available In the properties tab

Now to arrange icons on the screen, the app does not have a grid system. Instead of the palette menu, there is a layout which has to be configured and anything within the layout can be arranged. So made a horizontal layout and placed a list finder inside for connecting Bluetooth.

To I replaced the list finder with a custom image that I had downloaded from

Then I made another horizontal layout, to notify if the Bluetooth is connected or not. Put a label block in it. Layout again and put an image there. Just as an icon for led array which I had designed. Now to place the buttons for the array. I placed the button and replaced with a custom image. I then spaced them out with intermediate spacers. Once the first row seemed okay repeated for the same for 5 rows

There are other elements like non-visible elements. The sensors, connectivity comes in that category. They are a part of the app but do not have a block or icon. Now since my app had Bluetooth, I have Bluetooth and clock as non-visible elements.

The spacing and the heights and widths may not always be correct. It's by trial and error that I came to this layout and also it depends on what one wants, or how he/she intends to design it.

 Now that my user interface is done I shifted to the blocks area to do the actual "programming " of the app.

This is the block screen

To explain about the block window

1.The built-in gives more option for content and conditions. The screen is where all the components are displayed. The blocks are again basically dragged and drop.

2.The screen is where the blocks are placed and components are built

3.If there are any overlaps or warning during the building of the components, is displayed here

4.This provides an option to shift to screens, if there more than one, or to add and delete screen

Placing block

First I started with making the Bluetooth connection. I Couldn't understand the Bluetooth connection myself. So I had a few references to educate myself.

So to explain what I've done. I've chosen the list picker and set two controls to it. What it must do before a client is picked and what it must after a client is picked. So the first part is when the list picker is clicked it will show all the Bluetooth connections available, their name and address.

Then once the client is selected, the label will display "CONNECTED" in green color if the connection failed it will display "NOT CONNECTED" in red. Now, this establishes a connection with the Bluetooth device. Now we'll have to configure how the received data should be handled.

Here we bring in the clock parameter.By default, the clock is set at 1000ms. Which means it will keep checking for data for that interval of time. So when the Bluetooth is connected, we check for the value in the loop. If the value is greater than 0, then we check what data is available to be received and input case, we should check if the led is on or not. If the value is greater than 0 then the label will display led is on and if not led is off

Now to program the buttons. Now I wanted to the button to send a character or a number when they are pressed. So when the Arduino program reads the character received it will light up that particular led. So made it in such a way that when the led is pressed a number is sent out. I assigned different numbers for each led.

This is how I made the app for controlling LED array.

Charlieplexing

I tried to do Charlieplexing in my output week but failed. I was determined to correct it this time and find out where I went wrong. So I started reading about Charlieplexing and found these two profiles on fabacademy who had done excellent documentation on Charlieplexing.

This helped me understand Charlieplexing better and realize where I went wrong. There is a formula to calculate the number of pins and the no of LED's they can control. I missed out on this in my previous week. I used 3 pins to control 9 led's where in actuality its possible to control only 6 led's with 3 pins

Each LED is controlled in a different way by powering up each pin separately.

By understanding this we can come with a set of combinations to light up individual lights separately and once that's understood its easy to form characters.

Now each grid has two values. Sending high and low to appropriate pins will light up that square. So in case to for a letter A, boxes such as CA,DA,AB,EB,AC,BC,DC,EC,AD,ED,AE and DE must be lit up. So having understood Charlieplexing, I went on to design the board using eagle. To find out how to design using eagle please click here

Used attiny 44 as a microcontroller with 2 power supply options. Once the design was done, exported the image and took it to Krita to makes final png for milling. To know how to use Krita please click here.

These are the final png files

The size was about 5cm x 5cm. I milled the board and it took about 30 mins.

The drill bit was worn out a little. So the edges and the surface of the board were not very smooth. Even after trying to mill the board again resulted in the edges were rough. Nonetheless, the board was workable. I soldered the board and it did take time and patience to solder the board with so many LED's and resistors.

Now its time to program and check the board.

Programming

The rest of the assignment is solely depended on programming. First I needed to check if the LED array is working. I used my FabISP to program and YAY I was able to upload the bootloader. Then I uploaded the following program and it was a delight to watch.

I then used Neils program to check with my Charlieplexing.

It was great to see how the LED’s were glowing especially after my failure with the first attempt.

Now that the Charlieplexing is working I needed to check if I'm able to use my app to control the board before I jump to master and slave communication. I had to check several references to do this. There were several factors involved in the Bluetooth, app, programming etc.

I followed the examples, directions set by these two people.

This is the code I uploaded to my led array board.

To break down the code. I first defined what my Rx and Tx pins are going to be to talk to my Bluetooth device. Then setting the led ports. The band at which the Bluetooth has to communicate. Then in the loop, the character that's is received from the Bluetooth is read.  So if the character is "1" then BA is high. (Refer matrix chart). Hence I did the same for rest of the characters as well. Once the code was uploaded I connected my Bluetooth with my led array and fired up the app on my phone.

I connected my phone to the Bluetooth and I didn't have any problem.

And then I pressed each button and YAY again, the led was glowing. I tried with each led and it was successful. !!!

And then I pressed each button and YAY again, the led was glowing. I tried with each led and it was successful. !!!

Networking

Now to do network communication I decided to use my TRI board that I made during week 7. The idea is to communicate with using Bluetooth to the TRI board and led array board, which will be controlled using the app that I had made. Now that I already have all the boards, it's just about programming them and connecting them together.

The LED array is already programmed, I didn't change much In the program, but I wanted to program the TRI board to light up different colors when even numbers are present. So the LED would light up when 2, 4 and 6 are pressed. This is the code for that

Once the code was uploaded I connected the device. So the overall idea is to communicate with the different board by wired and wireless modes. Here the Bluetooth is like the master which provides a command for the TRI board and LED array board.

I then connected all the boards together and tested it out.

And yes the program and the boards worked in perfect synchrony with each other.