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ti84: offset binary by 0x100 to free space for TI-specific stuff
Not yet tried on real hardware, but we should be getting pretty close...
This commit is contained in:
Virgil Dupras
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@ -8,11 +8,24 @@ screen. With a tiny font, the best we can get is a 24x10 console.
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There is, however, a built-in USB controller that might prove very handy.
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[Further reading](../../doc/ti8x.md)
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I haven't opened one up yet, but apparently, they have limited scavenging value
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because its z80 CPU is packaged in a TI-specific chip. Due to its sturdy design,
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and its ample RAM and flash, we could imagine it becoming a valuable piece of
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equipment if found intact.
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The best pre-collapse ressource about it is
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[WikiTI](http://wikiti.brandonw.net/index.php).
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As it is now, with its tiny screen and cumbersome keyboard, Collapse OS is
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not really usable on the TI-84+. One could imagine a scenario where one has a
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terminal and uses the TI-84+ through the link for its large amount of flash and
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RAM. But using it standalone? Nah, not even post-collapse.
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Therefore, this recipe is more of a "look, I run!" demo.
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## Recipe
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This recipe gets the Collapse OS BASIC shell to run on the TI-84+, using its LCD
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This recipe gets the Collapse OS interpreter to run on the TI-84+, using its LCD
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screen as output and its builtin keyboard as input.
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## Gathering parts
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@ -25,7 +38,7 @@ screen as output and its builtin keyboard as input.
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## Build the ROM
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Running `make` will result in `os.rom` being created.
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Running `make` will result in `stage1.rom` being created.
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## Emulate
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@ -38,6 +51,30 @@ Collapse OS prompt will appear. See `emul/hw/ti/README.md` for details.
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## Upload to the calculator
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### Background notes
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Getting software to run on it is a bit tricky because it needs to be signed
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with TI-issued private keys. Those keys have long been found and are included
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in `keys/`. With the help of the
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[mktiupgrade](https://github.com/KnightOS/mktiupgrade), an upgrade file can be
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prepared and then sent through the USB port with the help of
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[tilp](http://lpg.ticalc.org/prj_tilp/).
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That, however, requires a modern computing environment. As of now, there is no
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way of installing Collapse OS on a TI-8X+ calculator from another Collapse OS
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system.
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Because it is not on the roadmap to implement complex cryptography in Collapse
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OS, the plan is to build a series of pre-signed bootloader images. The
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bootloader would then receive data through either the Link jack or the USB port
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and write that to flash (I haven't verified that yet, but I hope that data
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written to flash this way isn't verified cryptographically by the calculator).
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As modern computing fades away, those pre-signed binaries would become opaque,
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but at least, would allow bootstrapping from post-modern computers.
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### Instructions
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**WARNING: the instructions below will wipe all the contents of your calculator,
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including TI-OS.**
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@ -4,6 +4,7 @@ RAMSTART 0x70 + CONSTANT LCD_MEM
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RAMSTART 0x72 + CONSTANT KBD_MEM
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0x01 CONSTANT KBD_PORT
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212 LOAD ( z80 assembler )
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: ZFILL, ( u ) 0 DO 0 A, LOOP ;
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262 LOAD ( xcomp )
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522 LOAD ( font compiler )
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: CODE XCODE ;
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@ -12,8 +13,40 @@ RAMSTART 0x72 + CONSTANT KBD_MEM
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: CREATE XCREATE ; ( for KBD tbls )
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: : [ ' X: , ] ;
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( TI-84+ requires specific code at specific offsets which
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come in conflict with Collapse OS' stable ABI. We thus
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offset the binary by 0x100, which is our minimum possible
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increment and fill the TI stuff with the code below. )
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0x100 JPnn, 0x15 ZFILL, ( 0x18 )
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0x100 JPnn, ( reboot ) 0x1d ZFILL, ( 0x38 )
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( handleInterrupt )
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DI,
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AF PUSHqq,
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( did we push the ON button? )
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0x04 ( PORT_INT_TRIG ) INAn,
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0 ( INT_TRIG_ON ) A BITbr,
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IFNZ,
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( yes? acknowledge and boot )
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0x03 ( PORT_INT_MASK ) INAn,
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0x00 ( INT_MASK_ON ) A RESbr, ( ack interrupt )
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0x03 ( PORT_INT_MASK ) OUTnA,
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AF POPqq,
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EI,
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0x100 JPnn,
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THEN,
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AF POPqq,
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EI,
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RETI,
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0x03 ZFILL, ( 0x53 )
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0x100 JPnn, ( 0x56 ) 0xff A, 0xa5 A, 0xff A,
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0xa7 ZFILL, ( 0x100 )
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( All set, carry on! )
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CURRENT @ XCURRENT !
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0x100 BIN( !
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282 LOAD ( boot.z80 )
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393 LOAD ( icore low )
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555 557 LOADR ( LCD low )
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@ -27,5 +60,5 @@ PC ORG @ 8 + !
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558 560 XPACKR ( LCD high )
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438 451 XPACKR ( print fmt readln )
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," : _ LCD$ KBD$ (ok) RDLN$ ; _ "
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ORG @ 256 /MOD 2 PC! 2 PC!
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ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
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H@ 256 /MOD 2 PC! 2 PC!
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