Sierra Wireless MC8775 Reference Manual page 104

MC87xx Extended AT Command Reference
Table 7-3: Voice command details (Continued)
Command
!AVRXPCMFLTR
=<profile>, <tap>,
<value>
!AVRXPCMFLTR?
<profile>, <tap>
Supporting Mini Cards:
•
MC8775V
•
MC8785V
•
MC8790V
•
MC8791V
•
MC8792V
104
Set / query the RX PCM filter tap
The MC87xx modem has a 7-tap PCM (Pulse Code Modulation) filter.
This command sets the RX PCM filter tap for the specified profile.
Note: This command is only useful when embedding the MC87xx
modem in a handset.
Mobile phones, PDAs or other handheld transmitters and receivers that
incorporate a GSM module are required to comply with the GSM 11.10
3GPP TS51.010 or 3GPP TS26.132 standard, or with national
standards or government regulations. To conform to the relevant
standard you may need to tune certain audio characteristics. This
command allows you to tune the receive PCM filter to alter audio
characteristics.
Settings are stored in non-volatile memory and persist across power
cycles.
Module-specific details:
•
MC8775V — The change to the audio system takes place immedi-
ately if the specified audio profile is active.
•
MC8785V / MC8790V / MC8791V / MC8792V — The change to the
audio system takes place the next time the sound device (re)starts.
The process of tuning the receive audio characteristics generally
involves these steps:
1.
Turn off the PCM filter (set <value> parameter to 0x0000 on Tap 6).
2.
Use test equipment to obtain a frequency response curve with the
passing mask.
3.
Identify the frequency bands that need correction in order to bring
the overall response within the bounds specified in the test case.
4.
Use a filter design tool to determine the filter coefficients, convert
to signed Q14 format, and enter the appropriate tap settings using
the !AVRXPCMFLTR command.
5.
Repeat the process until the specifications are met.
Usage:
•
AT!AVRXPCMFLTR=<profile>, <tap>, <value> sets the RX PCM
filter tap for the specified <profile>.
•
AT!AVRXPCMFLTR?<profile>, <tap> returns the filter setting
(<value>) for the specified <profile>.
(Continued on next page)
Description
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