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TOOL IDB-SWE-001
UART baud rate

Desktop only

Engineering tools are available only on desktop screens.

UART baud rate

UBRR / divider value, actual baud rate, and clock-error from MCU clock and target baud. Stay under 2% error for reliable async UART.

Clock divider chain bit time — µs
XTAL 16 MHz ÷ (UBRR+1) UBRR = 8 ÷ OSR 16× BAUD 115.2 k TX 8.68 µs bit→ start 8 data bits LSB→MSB stop
Engineering notes

Formula

  • UBRR = fclk / (OSR × baud) − offset
  • actual = fclk / (OSR × (UBRR + offset))
  • error = (actual − target) / target × 100

Error targets

  • <0.5%: rock solid even across temperature.
  • 0.5–2%: acceptable for short frames at room temp.
  • >2%: framing errors are likely — pick a different clock or use a fractional baud divider.
  • Crystal-based clocks beat internal RC for serial reliability.

Result

Live