TCS3415FN View Datasheet(PDF) - austriamicrosystems AG

Part Name

Description

Manufacturer

TCS3415FN

Digital Color Sensors

austriamicrosystems AG 

TCS3404, TCS3414 − Application Information: Software

Interrupts

The interrupt feature of the TCS3404/14 device simplifies and

improves system efficiency by eliminating the need to poll the

sensor for a light intensity value. Interrupt mode is determined

by the INTR field in the Interrupt Control Register. The interrupt

feature may be disabled by writing a field value of 00h to the

Interrupt Control Register (02h) so that polling can be

performed.

The versatility of the interrupt feature provides many options

for interrupt configuration and usage. The primary purpose of

the interrupt function is to signal a meaningful change in light

intensity. However, it also be used as an end-of-conversion

signal. The concept of a meaningful change can be defined by

the user both in terms of light intensity and time, or persistence,

of that change in intensity. The TCS3404/14 device implements

two 16-bit-wide interrupt threshold registers that allow the

user to define thresholds above and below a desired light level.

An interrupt will then be generated when the value of a

conversion exceeds either of these limits. For simplicity of

programming, the threshold comparison uses the Interrupt

Source Register (03h) to select which ADC channel

(1 through 4) to generate the interrupt. This simplifies

calculation of thresholds that are based on a percent of the

current light level. For example, it is adequate to use only one

channel (e.g. green channel) when calculating light intensity

differences since, for a given light source, channel values are

linearly proportional to each other and thus each value scales

linearly with light intensity.

To further control when an interrupt occurs, the TCS3404/14

device provides an interrupt persistence feature. This feature

allows the user to specify the length in time of the number of

consecutive ADC channel values for which a light intensity

exceeding either interrupt threshold must persist before

actually generating an interrupt. This can be used to prevent

transient changes in light intensity from generating an

unwanted interrupt. See Figure 38 regarding the number of

timer values provided.

Two different interrupt styles are available: Level and SMBus

Alert. The difference between these two interrupt styles is how

they are cleared. Both result in the interrupt line going active

low and remaining low until the interrupt is cleared. A level style

interrupt is cleared by setting the Interrupt Clear field in the

COMMAND register to 11b. The SMBus Alert style interrupt is

cleared by an Alert Response as described in the Interrupt

Control Register section and SMBus specification.

To configure the interrupt as an end−of−conversion signal so

that every ADC integration cycle generates an interrupt, the

interrupt PERSIST field in the Interrupt Control Register (02h) is

set to 000b. Either Level or SMBus Alert style can be used.

ams Datasheet

[v1-00] 2015-Nov-11

Page 41

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