Communication Protocols: UART, SPI, and I2C Quiz Quiz

Explore essential concepts of UART, SPI, and I2C communication protocols with this focused quiz, designed to assess and improve your knowledge of serial data transmission, connections, and protocol-specific characteristics. Enhance your understanding of embedded systems connectivity, bus arbitration, and practical protocol applications with challenging, scenario-based questions.

1. Key Features of UART

   Which of the following statements best describes how UART (Universal Asynchronous Receiver/Transmitter) communicates between devices?

   1. UART transmits data one bit at a time using a single data line for each direction and does not use a clock signal.
   2. UART allows multiple masters to communicate with multiple slaves over a shared data line.
   3. UART requires three data lines: MOSI, MISO, and SCLK.
   4. UART uses separate data and clock lines and operates synchronously.

   Explanation: UART uses asynchronous serial communication, transmitting data one bit at a time over separate Tx and Rx lines without needing a dedicated clock line, relying instead on predetermined data format and baud rate. Option B describes synchronous communication, which is incorrect for UART. Option C confuses UART with SPI, which uses MOSI, MISO, and SCLK lines. Option D inaccurately refers to I2C functionality instead of UART.

2. SPI Data Transfer Scenario

   In SPI communication, what is the primary reason for having separate MOSI and MISO lines between a master and a slave device?

   1. They allow asynchronous data exchange over a single line.
   2. They serve as clock lines for data synchronization.
   3. They enable full-duplex communication, allowing simultaneous data transmission and reception.
   4. They prevent data collisions in multi-master configurations.

   Explanation: The separate MOSI (Master Out Slave In) and MISO (Master In Slave Out) lines in SPI enable full-duplex communication, so data can be sent and received at the same time. SPI does not use asynchronous data exchange on a single line, making option B incorrect. Option C is incorrect because clock lines (SCLK) are different from data lines. Option D is irrelevant since SPI does not natively handle multi-master collisions using these lines.

3. I2C Addressing

   When using I2C communication with several devices on the same bus, how does the master device uniquely select a specific slave device for data transfer?

   1. By manually changing the logic voltage of the SDA line.
   2. By sending the slave's unique address before the actual data during transmission.
   3. By switching baud rates to select between devices.
   4. By using different physical lines for each slave device.

   Explanation: In I2C, each slave device is assigned a unique address, and the master initiates communication by sending this address before transferring data. Using different physical lines is characteristic of SPI's chip select and not applicable to I2C. Changing baud rates is unrelated to device selection, making option C incorrect. Manually changing the SDA line voltage does not select devices in I2C.

4. Bus Arbitration in I2C

   Suppose two masters try to take control of an I2C bus at the same time; what mechanism allows both devices to manage this situation without data corruption?

   1. I2C assigns fixed time slots to each master to communicate.
   2. I2C disables all other masters automatically until the communication ends.
   3. I2C uses address prioritization, so the master with the higher address always wins.
   4. I2C uses bus arbitration, where the master that keeps its data on the SDA line while monitoring wins control.

   Explanation: I2C masters perform bus arbitration by monitoring the SDA line and continuing only if the data matches the intended value, ensuring no data corruption if multiple attempts occur. Option B is incorrect because address priority does not determine control. Fixed time slots (option C) are not part of the standard I2C protocol, and option D does not reflect how I2C bus contention is resolved.

5. Protocol Application Example

   A designer needs to transfer a large amount of data rapidly between a microcontroller and a sensor with minimal pin usage but requires multiple devices on the same bus. Which protocol is most suitable for this scenario?

   1. SPI, because it can achieve high data rates with only two shared lines regardless of device count.
   2. UART, because it offers the fastest data rates for multiple devices using a single channel.
   3. SPI, because it supports both high speed and multiple devices with one chip select pin per device.
   4. I2C, because it supports multiple devices on two lines but at moderate speeds.

   Explanation: I2C is ideal for multiple devices on a common bus with minimal pin usage, but it does not reach the highest speeds. Option B is wrong because UART does not scale well for multiple devices. Option C is inaccurate since SPI requires an additional chip select line per device, increasing pin usage as devices are added. Option D is partly true regarding speed and device support but contradicts the requirement for minimal pins due to multiple chip selects.