CCS811 sensor not working

[Quinn]

I have two sensor: Si7021 and CCS811 connect to board (nRF51 DK). Si7021 work fine. CCS811 always return NRF_DRV_TWI_EVT_ADDRESS_NACK error. Anyone can give me a help?

[awneil]

So are you using the correct one of those two?

Be careful that an I2C Slave Address is just 7 bits, but some people quote it as a byte - including the R/W bit ...

See www.avrfreaks.net/.../1872781 - starting from "The discrepancy between talking of I2C addresses as 7 or 8 bits is very common..."