+
−There exist a number of tunable settings in the Iota ABB (the chip that performs
+
−A-to-D and D-to-A conversion for the voice path) and in the Calypso DSP which
+
−in TI's firmware architecture are meant to be configured through the audio mode
+
−facility of the RiViera Audio Service.  The ABB settings grouped under the audio
+
−mode are as follows:
+
−
+
−* The selection of which analog interface pins the downlink audio should be
+
−  sent to: EARN&EARP (earpiece), AUXON&AUXOP (auxiliary) or HSO (headset).
+
−
+
−* The selection of which analog interface pins the uplink audio should be taken
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−  from: MICIN&MICIP (main microphone), AUXI (auxiliary input) or HSMICP
+
−  (headset microphone).
+
−
+
−* The selection of AUXI input levels when this analog input is in use for the
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−  voice uplink.
+
−
+
−* Analog gains for the uplink, the downlink and the analog sidetone from the
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−  uplink input to the downlink output.
+
−
+
−* Selection of a special filter bypass mode for the voice downlink.
+
−
+
−* The selection of MICBIAS (or HSMICBIAS) voltage between 2.0 V and 2.5 V.
+
−
+
−The DSP voice path settings grouped under the audio mode are as follows:
+
−
+
−* The selection of the digital voice path as being between GSM and the ABB (the
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−  default for analog voice interfaces), between GSM and MCSI (the external
+
−  digital voice interface) or between MCSI and the ABB (non-GSM operation).
+
−
+
−* FIR filter coefficients for the voice uplink and for the voice downlink.
+
−
+
−* Enabling/disabling and configuration of the Acoustic Echo Cancellation (AEC)
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−  mechanism.
+
−
+
−The firmware paradigm for working with all of the above settings is as follows:
+
−
+
−* In a lab environment, each of the listed settings can be independently tweaked
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−  and read back through ETM packets over the RVTMUX debug serial interface; the
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−  corresponding fc-tmsh commands (matching TI's original Windows-based TMSH)
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−  are auw for writing individual audio parameters and aur for reading them back.
+
−
+
−* In end-use operation, TI's intent as realized in the firmware design is that
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−  all of the listed audio settings will only be changed as a group, loaded from
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−  audio mode configuration files in FFS.
+
−
+
−Each audio mode configuration needs to be assigned a name between 1 and 9
+
−characters long, and for each named configuration there are two files in FFS:
+
−
+
−/aud/modename.cfg is the main configuration file
+
−/aud/modename.vol is the corresponding volume setting file
+
−
+
−This paradigm is a good fit for "dumbphone" handsets in which there usually
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−will be several different voice audio configurations for classic handheld
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−operation, for the hands-free loudspeaker mode, for operation with a wired
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−headset, and if the phone uses a loudspeaker (as opposed to a piezo buzzer) to
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−play ringtones and uses the Calypso DSP to generate those ringtone melodies,
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−there will also need to be an output-only audio configuration for ringing.
+
−
+
−How do the audio mode config files under /aud come into being?  It appears that
+
−TI's original intent was that a configuration would be manually constructed on
+
−a test device via TMSH auw commands, saved in the FFS of that test device with
+
−the aus command, then read out of that test device FFS in binary form and
+
−reuploaded as an opaque blob to all devices on the production line.  One can do
+
−the same procedure with our fc-tmsh and fc-fsio which fully replicate the
+
−relevant functionality of TI's original TMSH (to the best of our knowledge),
+
−but in FreeCalypso we have an alternate way which fits better with our UNIX
+
−philosophy: we have created our own ASCII text format for representing all of
+
−the content in TI's /aud/*.cfg binary files and tiaud-* utilities for compiling
+
−TI's binary cfg files from our ASCII source format, disassembling a *.cfg file
+
−read out of FFS into the same ASCII format, and creating the required *.vol
+
−companion files, which are also binary.
+
−
+
−A note about volume settings: the Iota ABB has two variable gain controls in
+
−the voice downlink path: the main "volume" gain in rather coarse 6 dB steps
+
−(the choices being 0 dB, -6 dB, -12 dB, -18 dB, -24 dB and mute) and a finer
+
−"calibration" gain in 1 dB steps between -6 and +6 dB.  It appears that TI's
+
−intent was that only the coarse volume control in 6 dB steps is to be visible
+
−to the user, with just 5 possible non-mute volume levels, and that the finer
+
−gain control be set at the factory in the audio mode config files for each mode
+
−as some form of calibration.  Pirelli DP-L10 significantly deviates from this
+
−model by providing 10 non-mute volume levels to the user with 2 dB or 3 dB steps
+
−between them by changing both VOLCTL and VDLPG fields in the VBDCTRL register,
+
−but at the present time we have no plans to make a similar drastic change in
+
−FreeCalypso.
+
−
+
−Another noteworthy feature of the audio mode system with respect to volume
+
−control is that there is a separate *.vol file that stores the current volume
+
−setting for each mode.  In a "dumbphone" handset firmware built according to
+
−TI's paradigm, the /aud/*.cfg files will be written once on the factory
+
−production line and only read afterward, but whenever the user turns the volume
+
−up or down in the UI, the *.vol file _corresponding to the current mode_ will
+
−be updated by the running fw.  Thus the fw would maintain a separate notion of
+
−the current volume for ringing, for the earpiece speaker, for the hands-free
+
−loudspeaker and for the wired headset, something which Pirelli's fw very
+
−notoriously fails to do.
+
−
+
−Default audio configuration
+
−===========================
+
−
+
−The default audio config set in the Iota ABB registers and in the DSP when no
+
−named audio mode config has been loaded with the audio_mode_load() API call
+
−(accessible via AT@AUL or via fc-tmsh aul command) is as follows, in the syntax
+
−which our tiaud-compile utility accepts as input and which our tiaud-decomp
+
−utility emits as output:
+
−
+
−voice-path 0
+
−mic default {
+
−	gain 3
+
−	output-bias 0
+
−	fir  0 0x4000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir  8 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir 16 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir 24 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−}
+
−speaker ear+aux {
+
−	gain 0
+
−	audio-filter 0
+
−	fir  0 0x4000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir  8 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir 16 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−	fir 24 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+
−}
+
−sidetone -5
+
−aec 0 0 0 0 0
+
−
+
−The meaning is as follows:
+
−
+
−* voice-path is the DSP digital voice path setting, 0 means the standard
+
−  configuration with the voice channel going between GSM and the local analog
+
−  voice hardware attached to the ABB.
+
−
+
−* The default microphone input is used for the voice uplink (MICIN&MICIP pins),
+
−  whereas the voice downlink is presented on both EARN&EARP and AUXON&AUXOP
+
−  pins, i.e., both "ear" and "aux" VDL amplifiers are enabled.
+
−
+
−* The microphone gain is 3 dB, the fine gain adjustment in the voice downlink
+
−  path is 0 dB, and the sidetone gain is -5 dB.
+
−
+
−* output-bias 0 under mic means that the MICBIAS voltage is set to 2.0 V.
+
−
+
−* audio-filter 0 under speaker means that the VFBYP bit in the VBCTRL1 register
+
−  is NOT set, i.e., the normal configuration.
+
−
+
−* DSP FIR filters do nothing, as coefficient 0 is set to unity and all other
+
−  coefficients are set to zero.
+
−
+
−* The AEC mechanism in the DSP is disabled.
+
−
+
−Creating your own audio mode configurations
+
−===========================================
+
−
+
−The input to our tiaud-compile utility can contain every setting shown in the
+
−default case above, or any desired subset thereof.  For any settings not given
+
−in the input, the defaults from the above will be used, except that
+
−tiaud-compile's current default for the speaker mode is just ear rather than
+
−ear+aux.  (It is a default which you should NOT depend on; set it explicitly if
+
−it matters!)  A few notes:
+
−
+
−* For all settings given as numbers, the number given in the ASCII input is the
+
−  number that goes into TI's binary structure, without any transformation, even
+
−  in those cases where the result is counter-intuitive, such as "audio-filter 0"
+
−  meaning that the filter is *enabled*.
+
−
+
−* The 3 possible mode keywords for the mic mode are default, aux and headset,
+
−  corresponding to MICIN&MICIP, AUXI and HSMICP analog inputs, respectively.
+
−
+
−* The 5 possible mode keywords for the speaker mode are ear, aux, headset,
+
−  buzzer and ear+aux.  The buzzer speaker mode exists only on TI's Nausica ABB
+
−  predating Iota, i.e., it won't work on any of the Calypso+Iota+Rita devices
+
−  built or supported by FreeCalypso, but our tiaud-compile and tiaud-decomp
+
−  utilities support it because it is nominally supported by TI's RiViera Audio
+
−  Service and its binary data structure for audio mode configuration.
+
−
+
−* When mic is set to aux, an additional mic setting called extra-gain becomes
+
−  available.  If extra-gain is set to 0, the AUXI gain will be set to 28.2 dB,
+
−  if extra-gain is set to 1, the AUXI gain will be set to 4.6 dB; all other
+
−  values will be considered invalid by the firmware.
+
−
+
−* Each of the two FIR filters in the DSP (one for uplink, one for downlink) has
+
−  a total of 31 coefficients, numbered 0 through 30, inclusive.  In the ASCII
+
−  input to tiaud-compile you can put each coefficient on its own fir line, put
+
−  all 31 coefficients on the same line, or group them in any other way you like.
+
−  The grouping used in the tiaud-decomp output has been chosen for line length
+
−  reasons.
+
−
+
−* The numbers given on fir and aec lines are 16-bit values that go directly into
+
−  the DSP; the former are FIR coefficients and the latter are bit masks.  They
+
−  can be given as either decimal or hexadecimal with 0x prefix in the ASCII
+
−  input to tiaud-compile.