Dsp Fir Filter - Renesas RX231 User Manual

Hear-it! Solution Kit
Transmit buffer:
pcm_buffer_tx
S/w attenuation
function
DSP FIR
Filter
Receive
buffer:
pcm_buffer_rx
6.2.3

DSP FIR Filter

As seen in Figure 6-5, the selected DSP FIR filter profile is applied to the sampled audio information when it is
transferred from the receive buffer pcm_buffer_rx to the transmit buffer pcm_buffer_tx. There are 4 pre-set filter
profiles; FLAT, LPF, HPF and BPF, defined for a sampling frequency of 24kHz.
These filter profiles are defined in the following files, located in the r_dsp_fir subfolder:
These profiles are used to initialise the DSP fir filter, which is then called repeatedly to act on the audio
information being transferred, in the file r_dsp_fir.c.
For further information concerning the DSP filter and its API, refer to the Renesas document R01UW0128ES
which is located within the DSP Library c-source download on the Renesas website.
Various tools are available for creating FIR filter profiles on the internet, but it is beyond the scope of this
document to investigate this further.
R12UZ0012EG0110 Rev. 1.10
Apr 03, 2017
Update
Tx Buffer
Transfer
end
interrupt
DMAC1
Transfer
end
interrupt
Update
Rx Buffer
Main routine: main()
Figure 6-5 : Data Transfer Scheme in Audio Streaming Mode
FLAT
LPF
HPF
BPF
isr_dmac_wr
DMAC0
SSI
Module
isr_dmac_rd ()
coef_flat_i32.h
coef_lpf1k_i32.h
coef_hpf1500_i32.h
coef_bpf_200_8000_i32.h
6 Description of Software
SSITX empty
interrupt
WM8983
SSIRX full
interrupt
Data
Operation
Interrupt
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