I am trying to use port expander PCF8574 attached to SAM C21 using Atmel Start.
But anything I try I get NACK on sending
uint8_t ab; int32_t res; struct io_descriptor *I2C_0_io; res=i2c_m_sync_get_io_descriptor(&I2C_0, &I2C_0_io); res=i2c_m_sync_enable(&I2C_0); res=i2c_m_sync_set_slaveaddr(&I2C_0, 0x4e, I2C_M_SEVEN); ab=0xff; res=io_write(I2C_0_io, &ab, 1);
The PCF8574 ist hooked up to PA16 and PA17 with 10k pullups and everything seems to be set up correctly in Atmel Start.
I am not very familar with I2C ... please help!