FreeCalypso > hg > freecalypso-tools
annotate rvinterf/doc/README.older @ 407:19e5a3e2f9c0
fcup-settime: moved time() retrieval a little closer to the output
A fundamental problem with all simple time transfer tools is that there is
always some delay between the time retrieval on the source system and that
transmitted time being set on the destination, and the resulting time
on the destination system is off by that delay amount. This delay cannot
be fully eliminated when working in a simple environment like ours,
but we should make our best effort to minimize it. In the present case,
moving the atinterf_init() call before the time() retrieval should make
a teensy-tiny improvement.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sat, 11 Aug 2018 21:52:17 +0000 |
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1 I (Spacefalcon the Outlaw, FreeCalypso developer) am still learning what kinds |
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2 of traffic may be passed across TI's RVTMUX binary-packet serial interface. We |
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3 already know that much of this traffic is debug trace output, i.e., |
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4 unidirectional and essentially unconditional output from the GSM device. All |
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5 of the "standard" firmwares we have (mokoN, our leo2moko which functions almost |
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6 identically, and Pirelli's fw) produce massive volumes of such trace output in |
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7 normal operation. We already know that this "unsolicited" trace output comes |
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8 in at least 3 different flavors: |
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9 |
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10 * RiViera traces emitted by rvf_send_trace() |
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11 * L1 traces |
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12 * G23 traces |
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13 |
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14 The RVTMUX interface can be used for more than just trace output, though: any |
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15 component in TI's fw suite can send and/or register to receive binary packets. |
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16 As I slowly work my way through various components which comprise TI's Leonardo |
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17 fw whose semi-source we use as our reference version, learning what they do and |
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18 reintegrating them in our own gsm-fw, I will undoubtedly uncover additional uses |
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19 to which the RVTMUX interface is put. |
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20 |
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21 Aside from the trivial provision in the RVT module itself whereby an external |
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22 host can send a command to the target to set a filter masking some of the RV |
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23 trace output, so far the only entity I've come across which accepts packets from |
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24 an external host is ETM (Enhanced Test Mode). ETM implements a registration |
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25 system of its own, whereby other modules can register with ETM to receive |
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26 certain external command messages passing first through RVT, then through ETM. |
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27 |
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28 Because I do not yet have a clear mental picture of *every* function for which |
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29 the RVTMUX interface will ever be used, it is correspondingly impractical to |
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30 decide on a once-and-for-all design of what the host-side software for talking |
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31 to this interface should be like. Therefore, it is currently premature to |
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32 expect any stability in the present rvinterf subdirectory of freecalypso-sw; I |
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33 may implement something one day, then toss it away the next day (without |
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34 providing much in the way of backward compatibility) when I come up with some |
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35 other idea. |
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36 |
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37 The current roadmap for what the rvinterf suite of host tools is envisioned to |
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38 look like eventually is as follows: |
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39 |
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40 rvtdump Opens the serial port, decodes TI's binary packet protocol, and |
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41 simply dumps every received/decoded packet on stdout in a human- |
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42 readable form. No provision for sending anything to the target. |
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43 Intended use: observing the debug trace output which all TI |
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44 firmwares emit as standard "background noise". This utility has |
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45 already been written, and it allows one to observe/log/study the |
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46 "noise" that appears on Pirelli's USB-serial port (running |
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47 Pirelli's original fw), as well as that emitted on the IrDA |
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48 (headset jack) port on the GTA02 by mokoN/leo2moko firmwares. |
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49 |
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50 rvinterf My plan is to make a copy of rvtdump, called rvinterf, and have |
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51 it act very much like rvtdump: receive TI's packets from the |
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52 serial port, decode them and print the decoded form on stdout. |
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53 However, rvinterf will also create a listening UNIX domain |
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54 socket to which other programs in the present suite will |
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55 connect. These other programs connecting through rvinterf will |
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56 be able to send packets to the target, as well as register to |
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57 receive certain kinds of target->host message packets. |
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58 |
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59 fc-tmsh FreeCalypso Test Mode Shell is my vision for the utility which |
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60 will provide a practically usable interface to ETM. ETM's |
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61 general mode of operation seems to be (weasel phrase inserted |
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62 because many other fw components may connect through ETM, and I |
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63 have yet to study all of them) command-response: an external |
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64 host sends a command to ETM, that command gets dispatched to the |
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65 proper registered handler, the command function is executed, a |
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66 response packet is composed, and finally that response is sent |
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67 back to the host. But because all code on the target side is |
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68 under active development and debugging, we should not expect |
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69 perfect lock-step behaviour on the interface; instead, our |
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70 fc-tmsh should be fundamentally asynchronous: when the user |
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71 enters a command, the appropriate command packet is sent to the |
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72 target, but we are prepared for target->host messages at any |
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73 time, without enforcing strict correspondence to issued |
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74 commands: let the developer-operator sort that out instead. |
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75 |
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76 The usage scenario I envision is that one will need to run rvinterf first |
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77 (either directly or through fc-xram) in one terminal window, leave it running, |
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78 then run fc-tmsh in another terminal window, and have it connect to rvinterf |
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79 via the local UNIX domain socket interface. Why such complexity, why not have |
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80 one program do everything? I suspect that in many debug/experimentation |
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81 sessions it will be necessary to use fc-tmsh on "noisy" targets, i.e., in |
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82 scenarios where the target is continuously spewing its "normal" voluminous debug |
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83 trace output, such that the "interesting" output as in responses to commands |
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84 gets drowned in the noise. In such a scenario it would be helpful to have one |
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85 terminal window in which one sees the transcript of the fc-tmsh session, |
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86 consisting of issued commands and received ETM responses without the general |
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87 noise, and another window in which one sees all RVTMUX interface activity in |
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88 real time - the latter would allow one to observe commands having side effects |
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89 outside of ETM, such as crashing the whole fw. :-) |