sercom i2c samd09

Hallo zusammen

Ich benutze einen SAMD09D14 und habe es geschafft das SERCOM USART 
Module ohne ASF zu benutzen. Beim I2C scheitert es allerdings, da ich 
auf den Pins überhaupt keine Signale bekomme.

Kann mir wer hier weiterhelfen?
Hier der i2C init:

/* port mux configuration*/
PORT->Group[0].PINCFG[PIN_PA22].reg = PORT_PINCFG_PMUXEN; /* SDA */
PORT->Group[0].PINCFG[PIN_PA23].reg = PORT_PINCFG_PMUXEN; /* SCL */

/*PMUX: even = n/2, odd: (n-1)/2 */
PORT->Group[0].PMUX[PIN_PA22/2].reg = 0x02;
PORT->Group[0].PMUX[PIN_PA23/2].reg = 0x20;

/* APBCMASK */
PM->APBCMASK.reg |= PM_APBCMASK_SERCOM1;

/*gclk configuration for sercom1 module*/
GCLK->CLKCTRL.reg =  GCLK_CLKCTRL_ID (SERCOM1_GCLK_ID_CORE) |
            GCLK_CLKCTRL_GEN(0) |
            GCLK_CLKCTRL_CLKEN;

/* set configuration for SERCOM1 I2C module */
SERCOM1->I2CM.CTRLB.reg = SERCOM_I2CM_CTRLB_SMEN; /* smart mode enable 
*/
while (SERCOM1->I2CM.SYNCBUSY.reg);

/* Set baudrate */
uint32_t fgclk    = 8000000;  /* 8MHz */
uint32_t fscl    = 100000; /* 100kHz SCL */
uint32_t trise    = 215; /* 215 ns rising time */
int32_t numerator  = fgclk - fscl*(10 + fgclk*trise/1000000000);
int32_t denominator  = 2*fscl;
int32_t tmp_baud = (int32_t)(div_ceil(numerator, denominator));
SERCOM1->I2CM.BAUD.bit.BAUD = SERCOM_I2CM_BAUD_BAUD(tmp_baud);
while (SERCOM1->I2CM.SYNCBUSY.reg);

/* enable module */
SERCOM1->I2CM.CTRLA.reg =  SERCOM_I2CM_CTRLA_ENABLE | 
SERCOM_I2CM_CTRLA_MODE_I2C_MASTER |  /* i2c master mode */
SERCOM_I2CM_CTRLA_SDAHOLD(3);    /* SDA hold time to 600ns */
while (SERCOM1->I2CM.SYNCBUSY.reg);

SERCOM1->I2CM.STATUS.reg |= SERCOM_I2CM_STATUS_BUSSTATE(1); /* set to 
idle state */
while (SERCOM1->I2CM.SYNCBUSY.reg);