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etm_audio.c: fix off-by-one error in auw of FIR coefficients This fix was already made in FC Tourmaline a while back, but it is also the kind of bugfix that deserves to be backported to Magnetite and Selenite as well.
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 31 Oct 2022 00:14:44 +0000
parents 2f880890c189
children
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1 Back when TI's TCS211 fw existed in the traditional world of phone handset and
3f1a587b3a84 doc/Voice-pseudo-modem written
Mychaela Falconia <falcon@freecalypso.org>
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2 cellular modem manufacturers, there were only two principal classes of target
3f1a587b3a84 doc/Voice-pseudo-modem written
Mychaela Falconia <falcon@freecalypso.org>
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3 devices for it: handsets and modems. The former have local UI hardware (LCDs
3f1a587b3a84 doc/Voice-pseudo-modem written
Mychaela Falconia <falcon@freecalypso.org>
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4 and keypads) and run firmware that works with this UI hw, the latter have no
3f1a587b3a84 doc/Voice-pseudo-modem written
Mychaela Falconia <falcon@freecalypso.org>
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5 such hw and run firmware that expects to be controlled by an external host via
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6 AT commands.
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7
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8 But the peculiar circumstances under which our FreeCalypso family of projects
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9 operates give rise to a third possibility: what happens if one were to run
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10 non-UI-capable firmware that expects control via AT commands on a hardware
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11 target device that was originally designed to be an end user phone handset, in
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12 our case either Motorola C1xx or Pirelli DP-L10? The result is what I call a
3f1a587b3a84 doc/Voice-pseudo-modem written
Mychaela Falconia <falcon@freecalypso.org>
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13 voice pseudo-modem (VPM): the phone's LCD stays dark, the buttons do nothing
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14 and the device expects to be controlled via AT commands as if it were a modem
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15 like the one in GTA01/02 smartphones, but there is no practically usable way to
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16 make use of any data services, only voice and SMS, hence my VPM term.
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17
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18 It needs to be noted clearly that the VPM hack described in this article is NOT
3f1a587b3a84 doc/Voice-pseudo-modem written
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19 a substitute for proper modem hardware - if your area of interest is Standard
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20 Modem functionality (the full set of GSM and GPRS services accessed via AT
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21 commands), then you need a proper hardware platform for it, such as our FCDEV3B
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22 hardware product. However, support for VPM operation in FreeCalypso exists for
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23 the following purposes:
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24
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25 * On some hw targets the VPM configuration can be an intermediate stepping stone
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26 toward potential future UI-enabled firmware (see the Handset-goal article) -
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27 this situation holds on the C139.
376
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28
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29 * Being able to run FreeCalypso fw in the VPM configuration on Mot C1xx hw that
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30 many people already have and that may still be readily and cheaply available
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31 makes our firmware accessible to those who are not able to afford our
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32 expensive FCDEV3B hardware.
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33
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34 * If you have a Pirelli DP-L10 phone (now very rare and hard to get, but were
3f1a587b3a84 doc/Voice-pseudo-modem written
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35 readily available in early 2013 when I started FreeCalypso): while there is
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36 unfortunately very little chance of being able to turn it into a practically
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37 usable Libre Dumbphone with FreeCalypso (the unwanted extra chips sans docs
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38 which we don't know how to power down are a killer), running FreeCalypso fw
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39 on the Pirelli in the VPM configuration is so easy and convenient that I do
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40 it all the time during development and testing.
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41
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42 Building firmware for VPM operation
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43 ===================================
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44
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45 The following two firmware build configurations (in the ./configure.sh sense)
3f1a587b3a84 doc/Voice-pseudo-modem written
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46 are appropriate for VPM usage:
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47
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48 hybrid-vpm This is the TCS2/TCS3 hybrid config (see the Modem-configs
3f1a587b3a84 doc/Voice-pseudo-modem written
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49 article) that has all data services (CSD, fax and GPRS)
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50 disabled and FCHG (new FreeCalypso battery charging driver)
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51 enabled. The removal of data services code makes the firmware
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52 image size and its RAM usage significantly smaller than all
3f1a587b3a84 doc/Voice-pseudo-modem written
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53 other configurations, making hybrid-vpm the smallest of all
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54 FC Magnetite firmware configs.
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55
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56 l1reconst-chg This is a variant of the stable l1reconst config (again, see
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57 the Modem-configs article) that has our FCHG battery charging
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58 driver enabled. Because this config uses the TCS211 blob
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59 version of the G23M PS, data services cannot be disabled, and
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60 the associated code sits in the firmware image as dead weight.
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61 Thus this l1reconst-chg config produces much heavier fw images
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62 than hybrid-vpm, and should only be used when you suspect a bug
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63 in the new TCS3 G23M or ACI code and would like to run the old
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64 TCS2 version for comparison.
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65
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66 Mot C139/140 and C155/156 phones have enough flash and RAM to run the
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67 l1reconst-chg config (with data services code as non-exercisable dead weight),
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68 but the more basic C11x/12x models (the ones with black&white LCDs) have
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69 smaller memories, and the only FC Magnetite config that is small enough to fit
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70 into their tiny flash and XRAM capacity is hybrid-vpm.
376
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71
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72 Playing with FreeCalypso VPM on C1xx phones
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73 ===========================================
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74
382
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75 If a Mot C1xx phone is flashed with a FreeCalypso firmware image in the VPM
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76 configuration (see C1xx-Howto for the messy details of how to do it), it will
376
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77 behave as follows:
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78
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79 * The LCD will remain dark and the buttons will do nothing no matter what.
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80
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81 * If you plug in Motorola's charging adapter (it's a regulated 5 VDC power
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82 source, but with a non-USB connector) and you had properly installed the
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83 charging config file when creating the aftermarket FFS for FreeCalypso, the
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84 battery will charge. When you unplug the charging adapter, if there is no
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85 host computer running FC host program rvinterf connected to the phone
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86 serially, the phone will power off some 15 to 20 s after the charger unplug.
376
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87
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88 * If you press the power button while the phone is off, even momentarily, the
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89 phone will power on and boot (with nothing on the LCD as usual), but if the
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90 headset jack serial port is not connected to a computer running rvinterf, the
509
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91 firmware will execute a power-off after at most 20 s.
376
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92
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93 * In order to make the phone-turned-VPM do anything useful, you will need to
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94 connect the headset jack serial port to a host computer running FC host tools,
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95 run rvinterf to keep the phone alive (keep it from automatically powering
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96 off), and use FC host utility fc-shell to issue AT commands to it over the
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97 RVTMUX channel managed by rvinterf.
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98
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99 * The phone will remain on (i.e., the fw won't execute an automatic power-off)
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100 for as long as there is either a charging power adapter plugged in or a
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101 connected host computer running rvinterf - if there is no charging power,
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102 the fw will send periodic keepalive queries to check for the presence of a
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103 connected rvinterf process.
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104
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105 Playing with FreeCalypso VPM on a Pirelli DP-L10
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106 ================================================
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107
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108 There are two ways in which one can play with FC VPM firmware on a Pirelli:
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109
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110 * FC VPM fw can be flashed into the phone just like on Mot C1xx. To make this
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111 approach sensible, you will also need to craft and install a charging config
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112 file that will cause our FCHG driver to initiate the charging process
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113 automatically when the battery voltage falls below some sensible threshold,
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114 without requiring manual charging start via AT@CHG=1. In this case the
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115 reflashed phone will behave like C1xx in the previous section, except that
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116 the charging power source and the host computer connection are one and the
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117 same in the case of Pirelli's USB.
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118
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119 * The other approach is to keep Pirelli's original fw in the flash, let the
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120 phone function normally when not in the middle of a FreeCalypso VPM session,
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121 and load our FC VPM fw into RAM via fc-xram, making use of this phone's huge
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122 RAM that can hold an entire functional fw image without flashing. This is
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123 the Mother's preferred method.
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124
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125 See the Pirelli-Howto article for the details.