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TOOL IDB-SWE-001

UART baud rate

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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

MCU clock Hz

Target baud bps

Oversampling

Register offset

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

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Ideambox Contact Privacy Policy TermsThat UART is also the production line's way into the board; the reference covers the test mode that runs on it. Firmware architecture and manufacturing test → Staff login