Audio Streaming Sample - Renesas RX231 User Manual

Hear-it! Solution Kit
3.2

Audio Streaming Sample

The second sample, rx231_dsp_demo, demonstrates the application of a DSP FIR filter on the left or right
channel of an incoming audio signal from the line-in or microphone inputs. The modified audio stream is then
transmitted to the audio codec via DMA and the SSI peripheral and then out to the speaker and/or headphones.
Figure 3-2 shows a holistic outline of the audio streaming. As with the USB playback demonstration, the volume
control is implemented with a software attenuation function, with an option in the source code for control via the
codec directly. There further configuration available in the source code to select the left or right channel as the
input source, and the left, right or both channels as output source.
The output volume can be controlled by adjusting the potentiometer, R43. Switch SW3 cycles between the
different FIR filter profiles; Flat, High Pass, Low Pass, Band Pass where the audio is playing.
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.
R12UZ0012EG0110 Rev. 1.10
Apr 03, 2017
Figure 3-2 : Audio Streaming Mode
3 Description of Application Firmware
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