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TIPI - TI-99/4A to Raspberry PI interface development

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So, @jrhodes asked if it was possible for TIPI to act as the cassette storage device as well. I always assumed due to some mis-reading of the console rom, that the GROM DSRs were looked at first, and then the expansion card ROMs... but that isn't true.


The console DSRLNK does go to expansion cards first, and then falls back on the GROM list. 


So, it is totally possible with a small change to the TIPI DSR ROM to include a device name for CS1, that the TIPI can service the PAB request first. And the TIPI can reject the request if not configured for it, return the to DSRLNK to resume scanning for other devices that might service CS1 and the real GROM CS1 device will be found and allowed to continue. Just like when DSK1 directories are not mapped...


There is at least one program that only supports CS1. Milton Bradley's Hangman. 


My implementation just delegates to TIPI's handling of a file in the TIPI. filesystem. All the weird things like loading Tidbit source as a BASIC Program Image file works for CS1 if that's what you map it to. There will be no prompts to rewind :)


I've added a setting in PI.CONFIG - CS1_FILE which should be set to the file name you want CS1 to read or write to. If it is empty, then no mapping is made, and the GROM DSR will kick in. I've updated TIPICFG so you can set this from the 4A easily. I have also updated the TIPI Web UI. There are some screen shots below. I'd be interested if anyone has a more intuitive recommendation for managing this. Maybe I'll through the word 'file' in there a few times to make it more clear it's not the same as all the DSK dir mappings. 


Feedback, and other thoughts are welcome. 


(Use of this feature will require a TIPI ROM upgrade, and TIPI services upgrade. TIPI services upgrade will not require the ROM upgrade, but the CS1 feature will simply not work.)



Here if CS1 is unmapped, you'll see a text box next to it so you can set the CS1_FILE mapping to whatever name or path you want. This should be a TI type path with '.' for directory separators, etc... and it should represent a file, not just a directory like the other mappings. Enter something, hit 'save' and your next interactions with CS1 will create or use that file.




Alternatively you may navigate to a file in the TIPI filesystem, select it, and then use the Action dropdown to choose 'Map to CS1', and submit... 





When it is set, you'll see the value. To unset the mapping, just click the red X next to it.





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If you are referring to adding DSK5-DSK9 to the TIPI DSR EPROM, coexistence will depend on the user's configuration and their program usage.  A few thoughts come to mind: 


With the /4A, the Horizon Ramdisk and its "partitions" are typically formatted starting with DSK5. to fully avoid conflicts with the floppy controller devices DSK1-4.  Devices DSK6-9 and DSKA-Z are also available to the Ramdisk.  If you are looking to expand the TIPI to emulate DSK5-9, the Horizon Ramdisk user can avoid conflicts by using Ramdisk drive letters A-Z.  Programs that are CRU-aware - such as FC or DU2K - become important for level 2 IO if there is a need for a Ramdisk device to use DSK5-9.   I don't know if any /4A users with both the TIPI and Ramdisk hardware use programs that do not allow DSK A-Z, with a need for Ramdisk drives 5-9.


The Geneve's boot EPROM reserves DSK6. for a Horizon Ramdisk boot device.  I cannot think of any other conflicts, since the Geneve OS manages its devices internally without utilizing the on-card DSR EPROMS. Theoretically, if the TIPI DSK6. mapping is not enabled and the TIPI DSR fails through to the next device, I doubt there would be any issues with the bootup sequence. 


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