# HG changeset patch # User Mychaela Falconia # Date 1539460888 0 # Node ID 8a15878740c18982eac2eec843d49f7b01aa3446 # Parent 16703b3fb211cb5cf888a9789773d066dd3c0f3c doc/C155-target article written diff -r 16703b3fb211 -r 8a15878740c1 doc/C155-target --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/doc/C155-target Sat Oct 13 20:01:28 2018 +0000 @@ -0,0 +1,64 @@ +In the early years of FreeCalypso, when we made our first attempt at FC GSM +firmware that was eventually retired under the name Citrine, we supported +running that fw on the Mot C155/156 target in addition to the other two C1xx +subfamilies. However, that C155 target support in not available in our current +Magnetite and Selenite firmwares. We are not doing any work to support that +target in our current fw because it does not provide anything of value that is +not better provided by other targets: + +* If your goal is to have a practically usable phone, the simpler C139/140 is a + better choice than C155/156: C155 uses a ringtone generator chip for which no + docs could be found, thus we may not be able to make it ring (in contrast, + C139 uses a piezoelectric buzzer driven by the Calypso itself), and C155's + LCD controller is much less obvious than the one in the C139 - the latter + already works the way we like. + +* If instead you would like a platform for playing with non-UI modem firmware + (which is all that our previous Citrine fw provided), then the only platform + which we officially support and endorse for that purpose is our own FCDEV3B. + It is not reasonable at this point to ask us to expend unpaid volunteer time + to support a hardware platform that is not made or sold by us when instead + you should be supporting our work by buying the hardware which we do make. + +If you wish to strike out on your own and try to resurrect C155 target support +in FC Selenite or Magnetite, your first difficulty will be that you won't be +able to run our fw entirely out of RAM without flashing like we did when running +Citrine on this target. FC Citrine implemented an FFS-in-RAM hack as an +alternative to using a real FFS in flash, but this hack is not present in +Magnetite or Selenite, thus unless you go even further out and resurrect that +hack as well, you will have to flash your firmware. If you take the route of +flashing your fw, you will have to decide between one of two possible +approaches: + +Approach 1: you can keep this target's original bootloader that expects the +main fw image to begin at 0x20000 with a hand-off interface that is new to the +C155 (different from the more basic C1xx subfamilies), and build your fw to fit +this C155 boot interface. This approach was supported in Citrine (although not +actually used because it was much easier to run via fc-xram w/o flashing) and +can be easily resurrected in the gcc build of Selenite. However, it would be a +lot more difficult to get this approach to work with TI's original TMS470 +environment: doing so would require major surgery on their assembly code and +linker script magic, which I am not comfortable with because we have no docs or +sources for those assembler and linker tools. You will also face the same +problem if you resurrect our old FFS-in-RAM hack and try to build a fw image +that runs entirely out of RAM w/o flashing: it is easy to do in the gcc +environment, but not in TMS470. + +Approach 2: you can replace the bootloader with the one we use on the more +basic C1xx phones (compal-flash-boot-for-fc.bin), in which case you will have +complications with loadtools (the ARM vs. Thumb entry point difference for +serially loaded code), but you can work around that issue by running fc-loadtool +and fc-xram with -h c155 -c plain instead of just -h c155 after you change the +bootloader, or you can create yet another patched bootloader version that does +the Thumb entry point for serially loaded code like C155 original but hands off +to the main fw in flash in the older C1xx fashion. Either way you will then be +able to build flashable fw images for this boot-modified C155 in the same manner +as how we do it for the more basic C1xx targets, and thus have both TMS470 and +gcc environments. + +As you can see from the above, it will be messy and unpleasant no matter which +way you lick it, and we (FreeCalypso Central) are not going to do this work for +free, whereas doing it on a commercial consulting basis would cost a lot more +than the $500 USD retail price of our own FreeCalypso development board +(FCDEV3B) that avoids all of these problems and is a much nicer platform for +Calypso sw/fw development.