FreeCalypso > hg > freecalypso-reveng
annotate frbl/README @ 401:4b6b595ae0a0
compal/boot/code-deriv: new analysis
| author | Mychaela Falconia <falcon@freecalypso.org> |
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| date | Sat, 14 Jan 2023 23:59:23 +0000 |
| parents | 814d3f24bed6 |
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| 336 | 1 TI's TCS211 firmware and its predecessors contain a flash-resident bootloader |
| 2 stage which we call FRBL. This FRBL implements not one but two different | |
| 3 protocols for interrupting the normal fw boot process, downloading a code image | |
| 4 into RAM and jumping to it; we call these two protocols FRBL1 and FRBL2. The | |
| 5 reasons for this oddity are historical: the original FRBL (TI GSM bootloader or | |
| 6 TI GSM monitor or whatever it was called officially) consisted of cmdboot.c, | |
| 7 command.c, convert.c, optboot.c, serial.c and start.c source modules and | |
| 8 implemented the protocol we call FRBL1, then came MMJ and other TIDK people | |
| 9 with their new FLUID idea, they decided on a different protocol which we call | |
| 10 FRBL2, and they jerry-rigged their new FLUID bootloader into the firmware's | |
| 11 FRBL code. | |
| 12 | |
| 13 The original source for FRBL1 C modules appears to have been lost (it is not | |
| 14 present in what we presume to be the world's last surviving copy of TCS211 from | |
| 15 OM), all we have are COFF objects from TI-OM's 20070608 build. The reconst | |
| 16 subdirectory contains our reconstruction attempt; this reconstruction is of | |
| 17 poor quality because these particular COFF objects have only minimal symbolic | |
| 18 information required for linking, as opposed to the much richer -g kind we got | |
| 19 for L1 and GPF. | |
| 20 | |
| 21 The test subdirectory is intended to contain our frbl1test and frbl2test | |
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22 programs; only frbl2test has been written so far. frbl2test implements the |
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23 host downloader side of the protocol we call FRBL2 in the same way how FLUID |
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24 (the PC-side application) implements it, allowing tests at both 115200 and |
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25 230400 baud as explained below. You need to provide a FreeCalypso-style (not |
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26 TI-style) S-record image to be fed to the target bootloader; helloapp from |
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27 freecalypso-tools/target-utils works ideally for this purpose. Because this |
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28 boot path does not go through the Calypso boot ROM, you will need to manually |
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29 select helloapp-irda.srec or helloapp-modem.srec, matching the Calypso UART you |
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30 are going through. frbl1test will work the same way if I ever get around to |
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31 writing it. |
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32 |
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33 230400 baud bogosity |
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34 ==================== |
| 336 | 35 |
| 36 Aside from implementing two different serial protocols, TI's FRBL as featured | |
| 37 in their Calypso firmwares has one other major quirk: both FRBL1 and FRBL2 were | |
| 38 implemented on 13 MHz platforms (the original purpose was to facilitate fw | |
| 39 loading on TI's earlier DBB chips before Calypso that didn't have the boot ROM | |
| 40 which we are so used to), on TI's D-Sample board (Calypso chip, 13 MHz CLKTCXO | |
| 41 input) both the old way (fluid -oO via FRBL or via JTAG) and the new way | |
| 42 (fluid -oo via the boot ROM) work well, but FRBL was never updated for 26 MHz | |
| 43 platforms, thus on all practical Calypso platforms (Leonardo derivatives) one | |
| 44 must use the boot ROM, not FRBL. | |
| 45 | |
| 46 TI's TCS211 builds for Leonardo and all vendor firmwares (Openmoko etc) derived | |
| 47 from this reference do include FRBL which was never updated for 26 MHz CLKTCXO | |
| 48 input on these platforms. The result is that FRBL will only work if you talk | |
| 49 to it at 230400 baud instead of TI's intended 115200 baud. TI's official | |
| 50 version of FLUID does not support FRBL entry at 230400 baud and such operation | |
| 51 was clearly never intended or officially supported - instead the officially | |
| 52 supported way for Leonardo and Leonardo-based customer designs was to use | |
| 53 fluid -oo mode, which works through the boot ROM just like fc-loadtool. | |
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54 |
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55 There is, however, an inexplicable mystery in that Openmoko seem to have used |
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56 fluid -oO mode somehow (at least with their version of FLUID that may have |
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57 unknown changes relative to TI's original) even though it should have never |
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58 worked at all. See this FreeCalypso community mailing list thread: |
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59 |
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60 https://www.freecalypso.org/pipermail/community/2020-March/000743.html |