Renesas RX231, Руководство пользователя

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Hear-it! Solution Kit 3 Description of Application Firmware
R12UZ0012EG0110 Rev. 1.10 Page 12 of 34
Apr 03, 2017
3. Description of Application Firmware
The Hear-it! Solution Kit is supplied with 2 sample applications. One sample, rx231_usb_playback_demo, plays
audio files in wav format from a USB mass storage device connected to the USB Host connector, CN9. The
second sample, rx231_dsp_demo, demonstrates the application of digital FIR filtering to an audio stream.
3.1 USB Playback Sample
This sample implements an audio player capable of rendering 48 kHz 16-bit WAV- PCM format file stored on a
USB device. A USB device can be attached to CN9 with a maximum of sixteen .wav files. Further details of the
configuration of the USB is detailed in section 4.2.4.
The .wav files will be displayed on the PMOD™ display and can be highlighted and selected for audio playback
using the on-board switch (SW3) and potentiometer (R43).
Audio information from the USB is sent by DMA transfer in I
2
S format to the audio codec via the SSI interface
for digital to analogue conversion and output to speaker and/or headphone. Once a .wav file is selected and
has started playing, the on-board potentiometer can be used to control the output volume. This volume control
is implemented with an attenuation function in the sample application software, or optionally by configuring the
volume on the WM8983 CODEC IC. Figure 3-1 gives a holistic outline the USB audio playback.
Figure 3-1 : USB Audio Playback
Caution:
Headphones should be connected to the 3.5mm line-out connector CN5. Connector CN6 is designed to
connect to a speaker only. It is not recommended to attach headphones to speaker connection CN6, as
damage to the headphones may occur. Refer to section 4.2.6 for further information.