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fc-loadtool help: improve language regarding 16 MiB flash chips In FC project history, 16 MiB flash originally meant Pirelli DP-L10. Then we got FCDEV3B with the same flash (our own design), but now we are discovering more Calypso devices that used such large flash, both late Calypso era (Sony Ericsson K2x0) as well as much earlier ones (FIC FLUID devices.txt file with 2004 dates, Leonardo+ rev 5). Hence we need to migrate to more generic or neutral language in associated documentation, without giving elevated status to specific examples that drove our early project history.
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 03 Dec 2023 21:11:12 +0000
parents 19cabe7c8e08
children
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19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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1 All standard phones and modems based on the Calypso chipset from TI implement
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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2 several different power saving modes, called sleep modes, and one of these sleep
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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3 modes has a profound impact on the operation of the externally visible UART
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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4 interfaces provided by the device. The power saving mode in question is called
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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5 deep sleep, and the phone or modem can only enter this deep sleep mode when it
19cabe7c8e08 doc/Deep-sleep-support article written
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6 is in the so-called idle state, meaning that it is camped on a cell and is ready
19cabe7c8e08 doc/Deep-sleep-support article written
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7 to receive incoming calls, messages or GPRS packets - deep sleep cannot be
19cabe7c8e08 doc/Deep-sleep-support article written
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8 entered while in an active call or in the middle of packet data transfer. When
19cabe7c8e08 doc/Deep-sleep-support article written
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9 a Calypso GSM device is idle with deep sleep enabled, it will only wake up at
19cabe7c8e08 doc/Deep-sleep-support article written
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10 preprogrammed intervals to listen on the paging channel, and will stay in deep
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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11 sleep in between these paging windows. Calypso GSM devices also enter deep
19cabe7c8e08 doc/Deep-sleep-support article written
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12 sleep when they are completely idle with no radio network connection.
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13
19cabe7c8e08 doc/Deep-sleep-support article written
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14 When a Calypso GSM device enters deep sleep, the main VCXO or VCTCXO that runs
19cabe7c8e08 doc/Deep-sleep-support article written
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15 at 13 or 26 MHz and provides all other clocks in normal operation is completely
19cabe7c8e08 doc/Deep-sleep-support article written
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16 stopped (powered off), and the only clock that remains running is the 32.768 kHz
19cabe7c8e08 doc/Deep-sleep-support article written
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17 watch crystal oscillator. The preprogrammed wakeup timing (waking up to listen
19cabe7c8e08 doc/Deep-sleep-support article written
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18 on the paging channel at the right time) is driven by this 32.768 kHz clock, but
19cabe7c8e08 doc/Deep-sleep-support article written
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19 the Calypso can also be woken up ahead of the programmed time by an external
19cabe7c8e08 doc/Deep-sleep-support article written
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20 interrupt such as a button press on the phone keypad.
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21
19cabe7c8e08 doc/Deep-sleep-support article written
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22 This deep sleep mode provides a very important power saving measure (the
19cabe7c8e08 doc/Deep-sleep-support article written
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23 extremely low current draw that is achieved during deep sleep is not possible
19cabe7c8e08 doc/Deep-sleep-support article written
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24 without stopping the fast clock), but it presents a real challenge for the
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Mychaela Falconia <falcon@freecalypso.org>
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25 external UART interfaces. Consider what happens when an external host sends
19cabe7c8e08 doc/Deep-sleep-support article written
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26 some characters to one of Calypso's UARTs (either the AT command interface or
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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27 RVTMUX) while the GSM device is in deep sleep. In normal operation a UART
19cabe7c8e08 doc/Deep-sleep-support article written
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28 requires a clock of 16x the baud rate (some vendors' UARTs can make do with
19cabe7c8e08 doc/Deep-sleep-support article written
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29 only 8x the baud rate) in order to receive asynchronous incoming characters,
19cabe7c8e08 doc/Deep-sleep-support article written
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30 and in the Calypso these UART clocks come from the 13 MHz master clock - but
19cabe7c8e08 doc/Deep-sleep-support article written
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31 that master clock is stopped during deep sleep!
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32
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33 Calypso UARTs have some special asynchronous (non-clock-dependent) logic that
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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34 causes a wakeup signal to be generated if some incoming traffic is detected at
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Mychaela Falconia <falcon@freecalypso.org>
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35 a UART while in deep sleep, but the first character that triggers this wakeup
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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36 will be lost: the asynchronous logic can detect that there is "something
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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37 happening" on the UART RxD line, but it cannot catch the actual byte content
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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38 without a clock: the *only* clock available during deep sleep is 32.768 kHz,
19cabe7c8e08 doc/Deep-sleep-support article written
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39 and even at 9600 baud one would need a clock several times faster than this
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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40 rate in order to receive and register an incoming byte. Furthermore, wakeup
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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41 from deep sleep takes a non-trivial length of time, thus if someone tries to
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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42 send lots of data to a Calypso UART while in deep sleep, quite a bit more than
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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43 just the first character will be lost: I did some experiments to characterize
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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44 the delay which needs to be inserted between the first "sacrificial" wakeup
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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45 character and the subsequent character which is expected to be received
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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46 correctly, and 40 ms wasn't enough, whereas 60 ms did the trick.
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47
19cabe7c8e08 doc/Deep-sleep-support article written
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48 So how can one have reliable communication with a Calypso GSM device over a
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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49 UART if the GSM device goes into and out of deep sleep at times which are
19cabe7c8e08 doc/Deep-sleep-support article written
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50 unpredictable to the external host and if sending characters to the Calypso
19cabe7c8e08 doc/Deep-sleep-support article written
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51 during deep sleep causes those characters to be lost? The solution involves a
19cabe7c8e08 doc/Deep-sleep-support article written
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52 special protocol:
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53
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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54 1) On the Calypso side, TI's reference firmware implements a UART activity
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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55 timer: every time some characters are received at a UART, the timer is reset to
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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56 10 s, and until that timer expires, the GSM device is not allowed to go into
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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57 deep sleep.
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58
19cabe7c8e08 doc/Deep-sleep-support article written
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59 2) Host systems sending command traffic to Calypso modems need to keep track of
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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60 how much time has elapsed since the last time they sent something to the modem,
19cabe7c8e08 doc/Deep-sleep-support article written
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61 and if enough time has elapsed that the modem is now allowed to enter deep
19cabe7c8e08 doc/Deep-sleep-support article written
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62 sleep, the host needs to perform a precautionary wakeup transmission before the
19cabe7c8e08 doc/Deep-sleep-support article written
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63 actual desired one.
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64
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65 What is a precautionary wakeup transmission? The idea is to send something to
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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66 the modem can be either accepted or lost by the latter: if the modem happens to
19cabe7c8e08 doc/Deep-sleep-support article written
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67 be awake at the time, the transmission will be received normally, and if the
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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68 modem is in deep sleep, the transmission will be lost but will cause the modem
19cabe7c8e08 doc/Deep-sleep-support article written
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69 to wake up and start the 10 s UART activity timer. Our FC host tools currently
19cabe7c8e08 doc/Deep-sleep-support article written
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70 use the following wakeup transmissions:
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71
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72 * On the AT command channel we send A-delay-T-delay-CR, i.e., AT and a carriage
19cabe7c8e08 doc/Deep-sleep-support article written
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73 return (3 characters total) with delays inserted in between; each of the two
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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74 delays is currently set to 30 ms based on empirical testing. We expect the
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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75 response to be either AT<newline>OK<newline> (echo of command followed by OK
19cabe7c8e08 doc/Deep-sleep-support article written
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76 response) if the modem was awake or just <newline>OK<newline> if we woke it up:
19cabe7c8e08 doc/Deep-sleep-support article written
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77 if we are waking the modem from deep sleep, our initial characters will trigger
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78 the wakeup sequence but will themselves be lost, and the modem is expected to
19cabe7c8e08 doc/Deep-sleep-support article written
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79 be awake with UARTs working by the time the CR comes in; we make use of a quirk
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80 of TI's AT command interpreter implementation in that sending a CR by itself
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81 produces a <newline>OK<newline> response.
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82
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83 * On the RVTMUX interface we send a string of 64 zero bytes followed by 100 ms
19cabe7c8e08 doc/Deep-sleep-support article written
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84 of delay; it is certainly overkill, but this approach was implemented back in
19cabe7c8e08 doc/Deep-sleep-support article written
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85 2013 (near the very beginning of FreeCalypso) and has worked without any
19cabe7c8e08 doc/Deep-sleep-support article written
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86 problems ever since, hence we are not changing it.
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87
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88 In the case of RVTMUX, our serial communication engine through which everything
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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89 funnels is rvinterf. Rvinterf will do the "wakeup shot" the first time it sends
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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90 anything to the target, and for all subsequent transmissions it will consider
19cabe7c8e08 doc/Deep-sleep-support article written
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91 the time since the last transmission: if it is greater than a set threshold
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92 (7 s by default), the wakeup shot is sent again. Thus there will be no
19cabe7c8e08 doc/Deep-sleep-support article written
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93 extraneous wakeup shots and associated delays during reasonably continuous
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94 back to back communication, but the wakeup shot delay will be incurred if
19cabe7c8e08 doc/Deep-sleep-support article written
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95 rvinterf is killed and restarted or if a non-trivial pause occurs in the
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96 communication flow.
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97
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98 In the case of AT commands, our fcup-* tools described in the User-phone-tools
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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99 article go through a back-end program called fcup-atinterf which does the serial
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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100 talking, and the latter helper program is responsible for the wakeup logic.
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Mychaela Falconia <falcon@freecalypso.org>
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101 However, fcup-atinterf is not a daemon like rvinterf, it is run anew for every
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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102 fcup-* user command, hence every fcup-* command currently involves the wakeup
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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103 delay step. It is certainly inefficient, but the underlying philosophy values
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104 reliability over efficiency.
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105
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106 The one remaining use case which has not been addressed at all yet is the GSM
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Mychaela Falconia <falcon@freecalypso.org>
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107 07.10 MUX; the current plan is to investigate it after the fc-host-tools-r9
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Mychaela Falconia <falcon@freecalypso.org>
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108 release and after we get FCDEV3B V2 boards which will hopefully be free from
19cabe7c8e08 doc/Deep-sleep-support article written
Mychaela Falconia <falcon@freecalypso.org>
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109 the sleep mode bug that afflicts FCDEV3B V1.