UM0224 datasheet(20/34 Pages) STMICROELECTRONICS

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Running the demonstrations

STR75x demonstration software

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2.4.3

Voice recorder

The STR750 microcontroller provides timers and an ADC module which can be used for

timing and signal acquisition respectively. In this case, we use one Timer (TIM0) to generate

an Update interrupt every 45.35 µs (22.05 KHz) which corresponds to the sampling

frequency of the ADC.

Note:

To fine tune the voice recording quality you can use the on board potentiometer RV3 to

control the micro preamplifier gain.

The following message is displayed on the LCD:

This LCD message remains until the "SEL" push button is pressed, then the MCU will erase

the SMI memory area that is used to store the voice data and the following message is

displayed on the LCD:

When KEY is pressed, the MCU starts recording voice and the following message is

displayed on the LCD:

To stop recording you may press the KEY button. Otherwise the MCU will stop it

automatically afer 30s.

2.4.4

Wave player

The STR750 microcontroller has several embedded Timers which can be used for timing

purposes and generating the output signals. In this case, we use 2 Timers (TIM) the first

Timer (TIM2) is configured to generate a PWM signal with a tunable duty cycle. The second

Timer (TIM0) is used to generate an Update interrupt each time the wave file is sampled

which corresponds to the TIM2 Duty cycle update.

The wave file has the following characteristics:

●

*.wav file

●

Audio Format: PCM

●

Sample rate: 8000 Hz/ 11025 Hz/ 22050 Hz/ 44100 Hz

●

Bits Per Sample: 8 bits

●

Number Of Channels: Mono

Start REC Voice

Voice Recorder

Record:Press KEY

Voice Recorder

Stop:in 30s/KEY

Voice Recorder

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