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Use asynchronous fractional mode to configure UART #86

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Merged
merged 1 commit into from
Jan 13, 2016
Merged

Use asynchronous fractional mode to configure UART #86

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31 changes: 12 additions & 19 deletions cores/arduino/SERCOM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -43,28 +43,21 @@ void SERCOM::initUART(SercomUartMode mode, SercomUartSampleRate sampleRate, uint

if ( mode == UART_INT_CLOCK )
{
uint16_t sampleRateValue ;
uint16_t sampleRateValue;

if ( sampleRate == SAMPLE_RATE_x16 )
{
sampleRateValue = 16 ;
}
else
{
if ( sampleRate == SAMPLE_RATE_x8 )
{
sampleRateValue = 8 ;
}
else
{
sampleRateValue = 3 ;
}
if (sampleRate == SAMPLE_RATE_x16) {
sampleRateValue = 16;
} else {
sampleRateValue = 8;
}

// Asynchronous arithmetic mode
// 65535 * ( 1 - sampleRateValue * baudrate / SystemCoreClock);
// 65535 - 65535 * (sampleRateValue * baudrate / SystemCoreClock));
sercom->USART.BAUD.reg = 65535.0f * ( 1.0f - (float)(sampleRateValue) * (float)(baudrate) / (float)(SystemCoreClock));
// Asynchronous fractional mode (Table 24-2 in datasheet)
// BAUD = fref / (sampleRateValue * fbaud)
// (multiply by 8, to calculate fractional piece)
uint32_t baudTimes8 = (SystemCoreClock * 8) / (sampleRateValue * baudrate);

sercom->USART.BAUD.FRAC.FP = (baudTimes8 % 8);
sercom->USART.BAUD.FRAC.BAUD = (baudTimes8 / 8);
}
}
void SERCOM::initFrame(SercomUartCharSize charSize, SercomDataOrder dataOrder, SercomParityMode parityMode, SercomNumberStopBit nbStopBits)
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5 changes: 2 additions & 3 deletions cores/arduino/SERCOM.h
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Expand Up @@ -86,9 +86,8 @@ typedef enum

typedef enum
{
SAMPLE_RATE_x16 = 0, //Arithmetic
SAMPLE_RATE_x8 = 0x2, //Arithmetic
SAMPLE_RATE_x3 = 0x3 //Arithmetic
SAMPLE_RATE_x16 = 0x1, //Fractional
SAMPLE_RATE_x8 = 0x3, //Fractional
} SercomUartSampleRate;

typedef enum
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