Owners manual

System

4.20. KEY_ADC

4.20.1. Overview

KEY_ADC is 6-bit resolution ADC for key application. The KEY_ADC can work up to 250Hz conversion rate.

The KEY_ADC includes the following features:

 Supports APB 32-bits bus width,reference voltage is 2.0V

 Support interrupt

 Support Hold Key and General Key

 Support Single Key and Continue Key mode

 Support 6-bits resolution

 Voltage input range between 0V to 2.0V

 Sample rate up to 250Hz

4.20.2. Operation Principle

The KEY_ADC converted data can accessed by interrupt and polling method. If software can’t access the last converted

data instantly, the new converted data would update the old one at new sampling data.

ADC_R E F

C on trol L og ic

K E Y _ D O W N _ IR Q

H O L D _K E Y _ IR Q

A L R E A D Y _H O L D _ IR Q

L R A D C _IN

Figure 4-14. KEY_ADC Converted Data Diagram

When ADC_IN Signal change from 1.8V to less than 1.35V (Level A), the comparator24 send first interrupt to control

logic; When ADC_IN Signal change from 1.35V to less than certain level (Program can set), the comparator25 give

second interrupt. If the control Logic get the first interrupt, In a certain time range (program can set), doesn’t get

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