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stm32f4: Improve serial baud rate calculation 

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2019-07-26 08:01:31 -04:00
parent f3d7287a28
commit 899b6726fa
1 changed files with 3 additions and 2 deletions
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5
src/stm32f4/serial.c
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@ -21,8 +21,9 @@ serial_init(void)
enable_pclock(USART2_BASE);
uint32_t pclk = get_pclock_frequency(USART2_BASE);
uint32_t div = pclk / (CONFIG_SERIAL_BAUD * 16);
USART2->BRR = div << USART_BRR_DIV_Mantissa_Pos;
uint32_t div = DIV_ROUND_CLOSEST(pclk, CONFIG_SERIAL_BAUD);
USART2->BRR = (((div / 16) << USART_BRR_DIV_Mantissa_Pos)
| ((div % 16) << USART_BRR_DIV_Fraction_Pos));
USART2->CR1 = CR1_FLAGS;
NVIC_SetPriority(USART2_IRQn, 0);
NVIC_EnableIRQ(USART2_IRQn);