SPI Baud Prescaler
Closest achievable SPI clock from a peripheral clock and prescaler, for STM32 and AVR.
Best match
Prescaler
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Actual SPI clock
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Error
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All prescaler values
| Prescaler | Actual SPI clock | Error (%) |
|---|
How it works
Most SPI peripherals (STM32 BR[2:0], AVR SPR1:0 + SPI2X)
only offer power-of-two clock dividers:
fSCK = fPCLK ÷ prescaler (prescaler ∈ {2, 4, 8, 16, 32, 64, 128, 256})
The tool evaluates every available prescaler and ranks them either by closeness to your target or by the highest clock that still stays at or below it — useful when a slave device specifies a hard maximum SCK frequency.