FreeCalypso > hg > fc-selenite
annotate doc/C155-target @ 119:7f0681afe430
RVTMUX_ON_MODEM config var brought over from Magnetite
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Wed, 07 Nov 2018 06:31:04 +0000 |
parents | 8a15878740c1 |
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rev | line source |
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8a15878740c1
doc/C155-target article written
Mychaela Falconia <falcon@freecalypso.org>
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1 In the early years of FreeCalypso, when we made our first attempt at FC GSM |
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2 firmware that was eventually retired under the name Citrine, we supported |
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3 running that fw on the Mot C155/156 target in addition to the other two C1xx |
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4 subfamilies. However, that C155 target support in not available in our current |
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5 Magnetite and Selenite firmwares. We are not doing any work to support that |
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6 target in our current fw because it does not provide anything of value that is |
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7 not better provided by other targets: |
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8 |
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9 * If your goal is to have a practically usable phone, the simpler C139/140 is a |
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10 better choice than C155/156: C155 uses a ringtone generator chip for which no |
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11 docs could be found, thus we may not be able to make it ring (in contrast, |
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12 C139 uses a piezoelectric buzzer driven by the Calypso itself), and C155's |
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13 LCD controller is much less obvious than the one in the C139 - the latter |
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14 already works the way we like. |
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15 |
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16 * If instead you would like a platform for playing with non-UI modem firmware |
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17 (which is all that our previous Citrine fw provided), then the only platform |
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18 which we officially support and endorse for that purpose is our own FCDEV3B. |
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19 It is not reasonable at this point to ask us to expend unpaid volunteer time |
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20 to support a hardware platform that is not made or sold by us when instead |
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21 you should be supporting our work by buying the hardware which we do make. |
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22 |
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23 If you wish to strike out on your own and try to resurrect C155 target support |
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24 in FC Selenite or Magnetite, your first difficulty will be that you won't be |
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25 able to run our fw entirely out of RAM without flashing like we did when running |
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26 Citrine on this target. FC Citrine implemented an FFS-in-RAM hack as an |
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27 alternative to using a real FFS in flash, but this hack is not present in |
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28 Magnetite or Selenite, thus unless you go even further out and resurrect that |
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29 hack as well, you will have to flash your firmware. If you take the route of |
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30 flashing your fw, you will have to decide between one of two possible |
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31 approaches: |
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32 |
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33 Approach 1: you can keep this target's original bootloader that expects the |
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34 main fw image to begin at 0x20000 with a hand-off interface that is new to the |
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35 C155 (different from the more basic C1xx subfamilies), and build your fw to fit |
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36 this C155 boot interface. This approach was supported in Citrine (although not |
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37 actually used because it was much easier to run via fc-xram w/o flashing) and |
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38 can be easily resurrected in the gcc build of Selenite. However, it would be a |
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39 lot more difficult to get this approach to work with TI's original TMS470 |
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40 environment: doing so would require major surgery on their assembly code and |
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41 linker script magic, which I am not comfortable with because we have no docs or |
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42 sources for those assembler and linker tools. You will also face the same |
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43 problem if you resurrect our old FFS-in-RAM hack and try to build a fw image |
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44 that runs entirely out of RAM w/o flashing: it is easy to do in the gcc |
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45 environment, but not in TMS470. |
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46 |
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47 Approach 2: you can replace the bootloader with the one we use on the more |
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48 basic C1xx phones (compal-flash-boot-for-fc.bin), in which case you will have |
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49 complications with loadtools (the ARM vs. Thumb entry point difference for |
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50 serially loaded code), but you can work around that issue by running fc-loadtool |
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51 and fc-xram with -h c155 -c plain instead of just -h c155 after you change the |
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52 bootloader, or you can create yet another patched bootloader version that does |
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53 the Thumb entry point for serially loaded code like C155 original but hands off |
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54 to the main fw in flash in the older C1xx fashion. Either way you will then be |
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55 able to build flashable fw images for this boot-modified C155 in the same manner |
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56 as how we do it for the more basic C1xx targets, and thus have both TMS470 and |
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57 gcc environments. |
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58 |
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59 As you can see from the above, it will be messy and unpleasant no matter which |
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60 way you lick it, and we (FreeCalypso Central) are not going to do this work for |
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61 free, whereas doing it on a commercial consulting basis would cost a lot more |
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62 than the $500 USD retail price of our own FreeCalypso development board |
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63 (FCDEV3B) that avoids all of these problems and is a much nicer platform for |
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64 Calypso sw/fw development. |