This week's class had a lot of new information, so it was quite difficult for me to follow everything. I had to finish most of this week without a lab, so I used TinkerCAD simulation to learn. Later in FabLab SP, I designed and made dedicated boards to complete requirements.
###Page Summary
1. Basics
2. Serial vs Parallel Communication
3. SPI protocol
4. UART
5. I2C
6. Design files
7. Links
---
1. Basics
---
Why Network?
1. Location
2. Parallelism
3. Modularity
4. Interference
To understand basics of communication protocols, this [basics of protocols series on circuitsbasics.com](https://www.circuitbasics.com/basics-of-the-spi-communication-protocol) was very useful. For effective communication between electronic devices, they need to use the same language. This language is called communication protocol. Some basic protocols are *SPI, I2C and UART.* These are generally slower than protocols like *USB, ethernet, bluetooth and wifi*, but are ideal for communication between microcontrollers and sensors where the large amounts of high-speed data does not need to be transferred.
Since I do not have access to a lab or a lot of inventory right now, I chose to understand wired communication protocols - SPI & I2C, with Arduino Unos that I do have access to. When I'm in the lab, or get more access to parts, I want to learn about the other wireless protocols too.
#### Serial vs Parallel Communication
2. Serial vs Parallel Communication
---
While communicating, bits are transferred from one device to another by quick changes in voltage. In a 5V system, O corresponds to 0V and 1 corresponds to 5V voltage.
In parallel communication, multiple bits are transferred at the same time through different wires. Whereas in series, the bits are transferred one after the other through the same wire. The following diagram shows the difference between the two.
Serial-Peripheral Interface (SPI) is a common communication protocol used by many devices like SD card modules, RFID card reader modules.
Unlike the other protocols (I2C and UART), SPI does not transfer data in packets. This means that any number of bits can be sent or received in a continuous stream without interruption in transmission.
Devices communicating via SPI are in a master-slave(secondary) relationship. The master is the controlling device (usually a microcontroller), while the slave (usually a sensor, display, or memory chip) takes instruction from the master.
...
...
@@ -43,8 +53,7 @@ This communication needs 4 lines:
*Synchronous (devices share clock) & serial communication
*1 master can talk to (theoretically) unlimited number of secondaries
How it works:
*Howit works:*
**Theclock** signal synchronizes the output of data bits from the master to the sampling of bits by the slave. One bit of data is transferred in each clock cycle, so the speed of data transfer is determined by the frequency of the clock signal. SPI communication is always initiated by the master since the master configures and generates the clock signal.
The clock signal in SPI can be modified using the properties of clock polarity and clock phase.
...
...
@@ -60,9 +69,9 @@ The master sends data to the secondary bit by bit, in serial through the **MOSI*
3. The master sends the data one bit at a time along the MOSI line. The secondary reads the bits as they are received.
4. If a response is needed, the secondary returns data one bit at a time to the master along the MISO line. The master reads the bits as they are received.
Universal Asynchronous Receiver/Transmitters (UART) are good to connect GPS modules, Bluetooth modules, and RFID card reader modules to Raspberry Pi, Arduino, or other microcontrollers.
Unlike SPI and I2C, UART is not exactly a communication protocol, but a physical circuit in a microcontroller, or a stand-alone IC. A UART’s purpose is to transmit and receive serial data.
...
...
@@ -76,17 +85,19 @@ It only uses two wires to transmit data between devices asynchronously, meaning
* 115200 maximum baud, avg is 9600 baud
* Asynchronous (without clock) & serial communication
* 1 master and 1 secondary
*How it works:*
**Start bit** When the receiving UART detects the high to low voltage transition, it begins reading the bits in the data frame at the frequency of the baud rate.
The **data frame** contains the actual data being transferred.
**Parity** describes the evenness or oddness of a number. If data has changed during transmission by electromagnetic radiation, mismatched baud rates, or long distance data transfers. 0 for even and 1 for odd, when the parity bit matches the data, the UART knows that the transmission was free of errors.
To signal the end of the data packet, the sending UART drives the data transmission line from a low voltage to a high voltage for at least two bit durations in the **stop bit**.
I2C communication allows for a single or multiple masters (unlimited) to talk to a single or multiple secondaries (max. 1008). It uses two wires to transmit data between devices. Since it follows series communication, it transfers bits one by one through the same wire.
Inter Integrated Circuit (I2C) communication allows for a single or multiple masters (unlimited) to talk to a single or multiple secondaries (max. 1008). It uses two wires to transmit data between devices. Since it follows series communication, it transfers bits one by one through the same wire.
**SDA(Serial Data)** - to send as well as receive data between the master/s and secondary/s
**SCL(Serial Clock)** - sends the clock signal
The clock signal is controlled by the master, and the data is *synchronized* to the bit sampling.
...
...
@@ -96,7 +107,7 @@ Data is sent in messages. Here is a diagram of the structure of a message.
A pull-up resistor needs to be connected from the Master's SDA and SCL each to VCC, if there are more than one secondaries or more than one masters.
Since I have access to some Arduino Unos, I tried [this guide on Instructables](https://www.instructables.com/Arduino-I2C-and-Multiple-Slaves/) to explore the communication between various numbers of masters and secondaries.
Since I have access to some Arduino Unos, I tried [this guide on Instructables](https://www.instructables.com/Arduino-I2C-and-Multiple-Slaves/) to explore the communication between varying numbers of masters and secondaries.
Arduino Uno has I2C pins:
**A5**is SCL
...
...
@@ -105,31 +116,49 @@ as shown in this [Arduino pinout diagram by pighixxx](https://commons.wikimedia.
