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Correct I2C frequency calculation formula #287

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Merged
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Jan 25, 2018
Merged

Correct I2C frequency calculation formula #287

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8 changes: 7 additions & 1 deletion cores/arduino/SERCOM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,12 @@
#include "SERCOM.h"
#include "variant.h"

#ifndef WIRE_RISE_TIME_NANOSECONDS
// Default rise time in nanoseconds, based on 4.7K ohm pull up resistors
// you can override this value in your variant if needed
#define WIRE_RISE_TIME_NANOSECONDS 125
#endif

SERCOM::SERCOM(Sercom* s)
{
sercom = s;
Expand Down Expand Up @@ -445,7 +451,7 @@ void SERCOM::initMasterWIRE( uint32_t baudrate )
// sercom->I2CM.INTENSET.reg = SERCOM_I2CM_INTENSET_MB | SERCOM_I2CM_INTENSET_SB | SERCOM_I2CM_INTENSET_ERROR ;

// Synchronous arithmetic baudrate
sercom->I2CM.BAUD.bit.BAUD = SystemCoreClock / ( 2 * baudrate) - 1 ;
sercom->I2CM.BAUD.bit.BAUD = SystemCoreClock / ( 2 * baudrate) - 5 - (((SystemCoreClock / 1000000) * WIRE_RISE_TIME_NANOSECONDS) / (2 * 1000));
}

void SERCOM::prepareNackBitWIRE( void )
Expand Down