Embedded Systems & Firmware

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?

  1. AAbout 14,400 bytes
  2. BAbout 11,500 bytes
  3. CAbout 115,200 bytes
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Answer: B. About 11,500 bytes

In 8N1 format, sending one byte of data takes 10 bits: 1 start bit, 8 data bits and 1 stop bit. 115200 ÷ 10 = 11,520, so about 11,500 bytes per second, or roughly 87 µs per byte. Heavy logging can take longer than expected and delay other processing, so the amount of output and the use of buffers need attention.

  • A. That divides by 8, ignoring the start and stop bits.
  • B. Correct. Each byte takes 10 bits.
  • C. That treats bits as bytes.
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