14. Networking and Communications

During this week, we worked on sending information between two boards, so that we ould get to understand better how is it possible to link a PCB with a mictocontroller to another one. During our group assignment, we reviewed some methods that work for serial communication, so that was clearer for me to make this week's practice based on that.

If you wish to check what we made and the communication method we followed, you may check our group assignment Here .

Also, If you're interested, here are some other communication protocols that exist:

Type of Communication	Details
Parallel Communication	Data Bus: Uses multiple lines to transmit data simultaneously. This is fast but requires many physical connections. Examples: PCI, ISA.
Serial Communication	UART (Universal Asynchronous Receiver-Transmitter): Asynchronous serial data transmission. Common in RS-232 connections. SPI (Serial Peripheral Interface): High-speed synchronous communication, useful for short distances. I2C (Inter-Integrated Circuit): Synchronous serial communication, suitable for short distances between multiple devices. USB (Universal Serial Bus): Universal serial protocol used to connect various peripherals. CAN (Controller Area Network): Used in automobiles and industrial systems for communication between microcontrollers. Ethernet: High-speed network communication, common in local and wide area networks.
Wireless Communication	Wi-Fi: High-speed connection through a wireless local area network. Bluetooth: Short-range communication, useful for peripherals and personal devices. RF (Radio Frequency): Used for long-range communication without wires.
Optical Communication	Fiber Optic: Uses light to transmit data at high speed and over long distances. Infrared: Communication through infrared signals, common in remote controls and some short-range devices.
Expansion Bus Communication	PCIe (Peripheral Component Interconnect Express): High-speed bus protocol mainly used in computers. VMEbus (Versa Module Eurocard): Used in industrial and defense systems. CompactPCI: Compact version of the PCI bus, used in telecommunications and industrial systems.
Industrial Bus Communication	Modbus: Serial communication protocol in industrial systems. Profibus: Fieldbus protocol used in industrial automation.

Getting started

As for this week I followed the I2C protocol, which is used for short-distance communication within a device or between multiple devices on the same bus.I had to understand better how it works and the implications to connect two or more boards together.
The main terms that you must know to start sending messages are the elements required to communicate:

Connection: SDA and SCL lines are connected to all devices on the I2C bus, often with pull-up resistors.

SDA

Purpose: Transfers data between devices in an I2C communication.
Function: Carries the actual data being transmitted.

SCL

Purpose: Carries the clock signal used to synchronize the data transfer between devices.
Function: Provides the timing signal that indicates when data can be read or written.

Master-Slave Relationship:One device acts as the master (initiates communication), others as slaves (respond to master).

Master ESP32S3 board + Arduino Uno slave + Neopixels

I started reviewing the connections of the boards I would be using. I knew I needed four pins on each board: SDA, SCL, PWR and GND. Some advise to share GND only, as a reference, but I chose to connect these 4. I located them in the Arduino Uno and "THE" Board I made for week 8 .
Then, I had to start the code for the Master. I included the Wire library to facilitate I2C communication. I defined the buttonPin as 6, where the button is connected, and set the slaveAddress to 9, which is the I2C address of the Arduino Uno slave.
To initialize the setup , I configured the buttonPin as an input with a pull-up resistor to ensure stable readings. I started the I2C communication as the master using Wire.begin(). Additionally, I initialized serial communication at 9600 baud rate for debugging purposes.
In the main loop, I checked the state of the button connected to buttonPin using digitalRead(). When the button was pressed (detected by its state changing from HIGH to LOW), I initiated transmission to the slave device at slaveAddress using Wire.beginTransmission().
I then sent a command ('1') to instruct the slave to change the NeoPixel color with Wire.write(). After sending the command, I ended the transmission using Wire.endTransmission(), updated the previous button state, and included a small delay to handle button bounce.
Next thing I did was to upload this code to the board I would use as my master. I recommend to send it before wiring anything together. Now It was time to code the Slave.
Int the code for the slave, I started b including both: the Wire library for the communication and the Adafruit NeoPixel library to control the NeoPixels. Also, defined the pin I would connect the neopixels to in the Arduino, this was 9 , and set NUM_PIXELS to as these are the ones I have in my board.
During setup, I initialized the Wire library to begin I2C communication, setting the Arduino Uno's address as 9 to act as the slave device, keeping the same I had on the master code. I registered a callback function (receiveEvent) to handle incoming I2C data.
Additionally, I initialized the NeoPixel strip using strip.begin() and turned off all LEDs by calling strip.show(). Serial communication was started at 9600 baud rate for debugging purposes.
Then I used the receiveEvent function for whenever data was received from the master. Within this function, I read the command sent by the master. If the command received was '1', I executed a sequence to change the color of all NeoPixels.
Finally, I updated the NeoPixel strip with new colors based on a predefined array of colors, then displayed these colors using strip.show().
Then, as I did with the master, I uploaded this code on the arduino as the slave. Now it was time to wire everything!
I wired the connections on my master board, and used the same colors as in the first diagram to avoid mistakes, then I connected it to the Arduino and I connected the Neopixel board to the arduino as well.
Then connected my master board to Power and pressed a button. It worked! Note: As you can see the LED on my board no longer works, if you connect something to another device make sure to use the right V+ and also use color coding for each wire, I accidentally burned mine :(.
Look at the color change! I put my resin cap on top to distribute the light better. This is the final result!