[参考译文] MSP430FR2355：在 MSP430FR2355 BSL 中处理 I2C 时钟卡在低电平

void I2C_FreeBus( I2C_Handle handle )
{
	I2C_Object *pObject;
	Uint32 SysTest, i;

	pObject = ( I2C_Object* )handle->object;

	/* Acquire the lock for this particular I2C handle */
	( void )SemaphoreP_pend( &pObject->mutex, SystemP_WAIT_FOREVER );

	/* Check if SDA or SCL is stuck low based on the SYSTEST.
	 * If SCL is stuck low we reset the IP.
	 * If SDA is stuck low drive 9 clock pulses on SCL and check if the
	 * target has released the SDA. If not we reset the I2C controller.
	 */
	SysTest = I2CControllerGetSysTest( pObject->baseAddr );

	I2C_CtrlInit( handle );

	/* SDA output high */
	/* generate 9 clk pulses on SCL */
	/* switch to system test mode */
	HW_SET_FIELD32( SysTest, I2C_SYSTEST_ST_EN, I2C_SYSTEST_ST_EN_ENABLE );
	HW_SET_FIELD32( SysTest, I2C_SYSTEST_TMODE, I2C_SYSTEST_TMODE_LOOPBACK );
	// HW_SET_FIELD32( SysTest, I2C_SYSTEST_SDA_O, I2C_SYSTEST_SDA_O_SDAOH );
	I2CControllerSetSysTest( pObject->baseAddr, SysTest );

	for( i = 0; i < 9; i++ ) {
		HW_SET_FIELD32( SysTest, I2C_SYSTEST_SCL_O, I2C_SYSTEST_SCL_O_SCLOH );
		I2CControllerSetSysTest( pObject->baseAddr, SysTest );
		Delay_us( 5 );

		HW_SET_FIELD32( SysTest, I2C_SYSTEST_SCL_O, I2C_SYSTEST_SCL_O_SCLOL );
		I2CControllerSetSysTest( pObject->baseAddr, SysTest );
		Delay_us( 5 );
	}

	/* Switch back to functional mode */
	HW_SET_FIELD32( SysTest, I2C_SYSTEST_ST_EN, I2C_SYSTEST_ST_EN_DISABLE );
	HW_SET_FIELD32( SysTest, I2C_SYSTEST_TMODE, I2C_SYSTEST_TMODE_FUNCTIONAL );
	I2CControllerSetSysTest( pObject->baseAddr, SysTest );

	/* Now check if the SDA is releases. If its still stuck low,
	* There is nothing that can be done. We still try to reset our IP.
	*/
	SysTest = I2CControllerGetSysTest( pObject->baseAddr );
	if ((SysTest & I2C_SYSTEST_SDA_I_FUNC_MASK) == 0U)
	{
	    I2C_CtrlInit( handle );
	}

	/* Release the lock for this particular I2C handle */
	( void )SemaphoreP_post( &pObject->mutex );
}

void I2C_CtrlInit( I2C_Handle handle )
{
	I2C_HwAttrs const *pHwAttrs;
	I2C_Object *pObject;
	Uint32 Delay = 50U;
	Uint32 OutputClk;
	Uint32 InternalClk;
	Uint32 RegVal;

	/* Get the pointer to hwAttrs */
	pObject = ( I2C_Object* )handle->object;
	pHwAttrs = ( I2C_HwAttrs const* )handle->hwAttrs;

	/* Put i2c in reset/disabled state */
	I2CControllerDisable( pObject->baseAddr );

	/* Do a software reset */
	I2CSoftReset( pObject->baseAddr );

	/* Enable i2c module */
	I2CControllerEnable( pObject->baseAddr );

	/* Wait for the reset to get complete -- timeout = 50ms */
	while( ( ( HW_RD_REG32( pObject->baseAddr + I2C_SYSS ) & I2C_SYSS_RDONE_MASK ) == 0 ) && ( Delay != 0 ) ) {
		Delay--;
		Delay_us( 1000 );
	}

	/* Put i2c in reset/disabled state */
	I2CControllerDisable( pObject->baseAddr );

	/* Configure i2c bus speed*/
	switch( pObject->i2cParams.bitRate ) {
	case I2C_100KHZ: {
		OutputClk = 100000U;
		InternalClk = I2C_MODULE_INTERNAL_CLK_4MHZ;
		break;
	}

	case I2C_400KHZ: {
		OutputClk = 400000U;
		InternalClk = I2C_MODULE_INTERNAL_CLK_12MHZ;
		break;
	}

	case I2C_1P0MHZ: {
		OutputClk = 3400000U;
		InternalClk = I2C_MODULE_INTERNAL_CLK_12MHZ;
		break;
	}

	default: {
		/* Default case force it to 100 KHZ bit rate */
		OutputClk = 100000U;
		InternalClk = I2C_MODULE_INTERNAL_CLK_4MHZ;
	}
		break;
	}

	/* Set the I2C configuration */
	I2CControllerInitExpClk( pObject->baseAddr, pHwAttrs->funcClk, InternalClk, OutputClk );

	/* Configure I2C_SYSC params
	 * Disable auto idle mode
	 * Both OCP and systen clock cut off
	 * Wake up mechanism disabled
	 * No idle mode selected
	 */
	RegVal = I2C_AUTOIDLE_DISABLE | I2C_CUT_OFF_BOTH_CLK | I2C_ENAWAKEUP_DISABLE | I2C_NO_IDLE_MODE;
	I2CSyscInit( pObject->baseAddr, RegVal );

	/* Configure I2C_CON params */
	RegVal = I2C_OPMODE_FAST_STAND_MODE | I2C_NORMAL_MODE;
	I2CConfig( pObject->baseAddr, RegVal );

	/* Take the I2C module out of reset: */
	I2CControllerEnable( pObject->baseAddr );

	/* Enable free run mode */
	I2CControllerEnableFreeRun( pObject->baseAddr );

	/*Clear status register */
	I2CControllerIntClearEx( pObject->baseAddr, I2C_INT_ALL );
}