TCS34721 datasheet(15/40 Pages) AMSCO

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[v1-02] 2016-Feb-08

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TCS3472 − Principles of Operation

The registers for programming the integration and wait times

are a 2’s compliment values. The actual time can be calculated

as follows:

ATIME = 256 − Integration Time / 2.4 ms

Inversely, the time can be calculated from the register value as

follows:

Integration Time = 2.4 ms × (256 − ATIME)

For example, if a 100-ms integration time is needed, the device

needs to be programmed to:

256 − (100 / 2.4) = 256 − 42 = 214 = 0xD6

Conversely, the programmed value of 0xC0 would correspond

to:

(256 − 0xC0) × 2.4 = 64 × 2.4 = 154 ms.

Interrupts

The interrupt feature simplifies and improves system efficiency

by eliminating the need to poll the sensor for light intensity

values outside of a user-defined range. While the interrupt

function is always enabled and its status is available in the

status register (0x13), the output of the interrupt state can be

enabled using the RGBC interrupt enable (AIEN) field in the

enable register (0x00).

Two 16-bit interrupt threshold registers allow the user to set

limits below and above a desired light level. An interrupt can

be generated when the Clear data (CDATA) is less than the Clear

interrupt low threshold (AILTx) or is greater than the Clear

interrupt high threshold (AIHTx).

It is important to note that the thresholds are evaluated in

sequence, first the low threshold, then the high threshold. As a

result, if the low threshold is set above the high threshold, the

high threshold is ignored and only the low threshold is

evaluated.

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