Embedded Systems & Firmware

What is a characteristic of serial communication with a UART?

  1. AThe sender drives a clock wire, and the receiver samples data with that clock
  2. BNo clock wire is used; both sides agree on a communication speed (baud rate), and a start bit marks each character
  3. CMany devices share one wire and are selected by address
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Answer: B. No clock wire is used; both sides agree on a communication speed (baud rate), and a start bit marks each character

A UART communicates asynchronously over two wires, transmit and receive (plus ground). The line idles at 1; a 0 start bit marks the beginning of a character, followed by the data bits and a 1 stop bit at the end. No clock is sent, so both sides must be configured for the same speed, such as 115200 bps. UARTs are commonly used for debug output and for connecting GPS and radio modules.

  • A. That is synchronous communication like SPI.
  • B. Correct. It is asynchronous serial communication.
  • C. Selecting by address is what I2C and similar do.
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More Embedded Systems & Firmware questions

  1. On a 115200 bps UART using 8 data bits, no parity and 1 stop bit (8N1), roughly how many bytes can be sent per second?
  2. A small baud-rate mismatch between UART transmitter and receiver can garble characters. Why is the tolerance limited to roughly a few percent?
  3. What is a characteristic of SPI communication?
  4. Which set of four signals is generally used by SPI?
  5. When an SPI part is connected but correct data cannot be read, which setting is most worth checking?