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Merge pull request #3894 from haukepetersen/opt_f0_baudcalc

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cpu/stm32f0: optimized baudrate calculation
This commit is contained in:
Peter Kietzmann 2015-09-29 21:01:37 +02:00
commit 15b5e09d9f
1 changed files with 4 additions and 4 deletions
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8
cpu/stm32f0/periph/uart.c
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@ -103,7 +103,7 @@ int uart_init_blocking(uart_t uart, uint32_t baudrate)
uint32_t rx_pin = 0;
uint32_t tx_pin = 0;
uint8_t af = 0;
float divider;
uint32_t mid;
uint16_t mantissa;
uint8_t fraction;
@ -157,9 +157,9 @@ int uart_init_blocking(uart_t uart, uint32_t baudrate)
}
/* configure UART to mode 8N1 with given baudrate */
divider = ((float)F_CPU) / (16 * baudrate);
mantissa = (uint16_t)divider;
fraction = (uint8_t)((divider - mantissa) * 16);
mid = (CLOCK_CORECLOCK / baudrate);
mantissa = (uint16_t)(mid / 16);
fraction = (uint8_t)(mid - (mantissa * 16));
dev->BRR = ((mantissa & 0x0fff) << 4) | (0x0f & fraction);
/* enable receive and transmit mode */