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AS7221

I²C Master Interface

Datasheet

• PUBLIC

DS000479

• v4-00 • 2019-Jun-28

│ 23

I²C Master Interface

External sensors with native support by the AS7221 can be added via the I²C master interface. For

example the ams current TSL25721 or legacy TSL45315 can be used to add daylighting operation to

the AS7221. Once the supported ambient light sensor is detected by the AS7221, and the daylighting

is activated by using the ATDL=1 command, daylighting operation begins. Native support is provided

for selected ams environmental sensors including temperature, humidity and air quality/VOC.

The I2C Master interface uses I2C serial protocol for communication with 7+1-bit chip addressing mode

and full-speed clock frequency. Read and Write transactions comply with the standard set by Philips

(now NXP).The I2C master interface can be used as a UART to I2C Bridge to connect to other I2C

external sensors that do not have native support in the smart lighting firmware. Supporting smart

lighting commands enable pass-through communications with non-natively supported devices.

8.1

I²C Protocol

Figure 19:

2C Symbol Definition

Symbol

Definition

Note

Start condition after stop

1-bit

Repeated start

1-bit

Slave address for write

Slave address

Slave address for read

Slave address

Word address

8-bit

Acknowledge

1-bit

No acknowledge

1-bit

Data

Data/write

8-bit

Data (n)

Data/read

8-bit

Stop condition

1-bit

WA++

Slave increment word address

During acknowledge

The above I²C symbol definition table describes the symbols used in the following Read and Write

descriptions.

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