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Merge pull request #3893 from haukepetersen/opt_f1_baudcalc

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cpu/stm32f1: optimized baudrate calculation
This commit is contained in:
Peter Kietzmann 2015-09-30 17:20:08 +02:00
commit 4e05254eb7
1 changed files with 3 additions and 4 deletions
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7
cpu/stm32f1/periph/uart.c
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@ -102,7 +102,6 @@ int uart_init_blocking(uart_t uart, uint32_t baudrate)
USART_TypeDef *dev; USART_TypeDef *dev;
uint32_t bus_freq; uint32_t bus_freq;
gpio_t rx_pin, tx_pin; gpio_t rx_pin, tx_pin;
float divider;
uint16_t mantissa; uint16_t mantissa;
uint8_t fraction; uint8_t fraction;
@ -136,9 +135,9 @@ int uart_init_blocking(uart_t uart, uint32_t baudrate)
gpio_init(rx_pin, GPIO_DIR_IN, GPIO_NOPULL); gpio_init(rx_pin, GPIO_DIR_IN, GPIO_NOPULL);
/* configure UART to mode 8N1 with given baudrate */ /* configure UART to mode 8N1 with given baudrate */
divider = ((float)bus_freq) / (16 * baudrate); bus_freq /= baudrate;
mantissa = (uint16_t)floorf(divider); mantissa = (uint16_t)(bus_freq / 16);
fraction = (uint8_t)floorf((divider - mantissa) * 16); fraction = (uint8_t)(bus_freq - (mantissa * 16));
dev->BRR = 0; dev->BRR = 0;
dev->BRR |= ((mantissa & 0x0fff) << 4) | (0x0f & fraction); dev->BRR |= ((mantissa & 0x0fff) << 4) | (0x0f & fraction);