STA321 View Datasheet(PDF) - STMicroelectronics
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Description
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STA321 Datasheet PDF : 157 Pages
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Digital processing stage
STA321
6.9.1
Configuration example
This is an example of the tone control register setup. It is assumed that every peripheral is
already configured and working correctly.
Table 21 gives the register values to obtain +12 dB of bass on all channels and -10 dB of
treble on channels 0 and 1.
Table 21. Selecting EQ curves
Register - Address Programmed value
Description
BASS_SEL0_R
0x38
CH0 +12 dB bass
BASS_SEL1_R
0x38
CH1 +12 dB bass
BASS_SEL2_R
0x38
CH2 +12 dB bass
BASS_SEL3_R
0x38
CH3 +12 dB bass
TREB_SEL0_R
TREB_SEL1_R
0x22
0xx22
CH0 -10 dB treble
CH1 - 10 dB treble
6.10
6.10.1
Programmable delay
Every channel, just after the biquads stage, is connected to a dedicated delay block.
The length of the delay is stored in RAM at location 0x128 and can vary from 0 to 35
samples. The corresponding time delay depends on the processing sampling frequency.
Presets
The delay of every channel is set to 0.
6.11
Volume and mute control
The STA321 provides a flexible volume and mute control stage. Using the registers VOLCH0
to VOLCH3 on page 122 it is possible to set the volume for each channel individually from
+36 dB to -105 dB with 0.5-dB steps.
There is a master volume control, register MVOL on page 120, as well. The master volume
adds an offset to all the individual volume settings.
The mute function offers the possibility to turn off the sound by reducing the volume setting
to -127.5 dB. It could be activated in two ways:
z register FFXCFG0 on page 82 provides a dedicated mute control for each channel.
z pin MUTE, driven by an external signal, puts all four channels into mute mode.
Register VOLCFG on page 120 provides some flexibility to set how the mute and volume
change procedures are applied. If bit SVOL_ONx is activated the volume of channel x is
changed gradually (soft volume or soft mute); using a ramp it starts from the current value
and goes down to the target value or to -127.5 dB for mute. The slope of the ramp is set with
with the value TIM_SVOL which represents how many samples are needed to achieve a
0.5-dB step.
tSTEP = 2TIM_SVOL / fS
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Doc ID 15351 Rev 3
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