Renesas RX231, Руководство пользователя

Страница: 28 / 34

Hear-it! Solution Kit 6 Description of Software
R12UZ0012EG0110 Rev. 1.10 Page 28 of 34
Apr 03, 2017
Figure 6-5 : Data Transfer Scheme in Audio Streaming Mode
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:
FLAT coef_flat_i32.h
LPF coef_lpf1k_i32.h
HPF coef_hpf1500_i32.h
BPF coef_bpf_200_8000_i32.h
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.
Transfer
end
interrupt
SSIRX full
interrupt
SSITX empty
interrupt
Transfer
end
interrupt
isr_dmac_wr
Main routine: main()
Transmit buffer:
pcm_buffer_tx
Receive
buffer:
pcm_buffer_rx
SSI
Module
S
tar
t DS
P
tr
ans
fer
WM8983
Data
Operation
Interrupt
DMAC0
DMAC1
isr_dmac_rd ()
S/w attenuation
function
Update
Rx Buffer
Update
Tx Buffer
DSP FIR
Filter