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Fix rounding error in baudrate calculation.

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This commit is contained in:
Ian Martin 2014-03-22 10:21:54 -04:00
parent e3c19714d4
commit 1ceb8ae358
1 changed files with 5 additions and 1 deletions
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6
cpu/cc2538/dev/uart.h
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@ -71,7 +71,11 @@
#define UART_CLOCK_RATE 16000000 /* 16 MHz */ #define UART_CLOCK_RATE 16000000 /* 16 MHz */
#define UART_CTL_HSE_VALUE 0 #define UART_CTL_HSE_VALUE 0
#define UART_CTL_VALUE ( UART_CTL_RXE | UART_CTL_TXE | (UART_CTL_HSE_VALUE << 5) ) #define UART_CTL_VALUE ( UART_CTL_RXE | UART_CTL_TXE | (UART_CTL_HSE_VALUE << 5) )
#define BAUD2BRD(baud) ( (UART_CLOCK_RATE << (UART_CTL_HSE_VALUE + 2)) / (baud) )
/* DIV_ROUND() divides integers while avoiding a rounding error: */
#define DIV_ROUND(num, denom) ( ((num) + (denom) / 2) / (denom) )
#define BAUD2BRD(baud) DIV_ROUND(UART_CLOCK_RATE << (UART_CTL_HSE_VALUE + 2), (baud))
#define uart_set_baudrate(baud) ( \ #define uart_set_baudrate(baud) ( \
REG(UART_BASE | UART_IBRD) = BAUD2BRD(baud) >> 6, \ REG(UART_BASE | UART_IBRD) = BAUD2BRD(baud) >> 6, \