Does anybody have schematics of a Dragon cartridge PCB? Or photos with desoldered parts, where one can see all the connections? What's beneath the 74LS00?
![Question :?:](./images/smilies/icon_question.gif)
Regards,
Rolo
You will not be able to write to an EPROM in that way. The EPROMs need a higher programming voltage and signal timings that the Dragon does not provide. You need a proper EPROM programmer to do that. You should be able to write to SRAM connected to the cartridge port.Rink wrote:However, writing to the EPROMs from the Dragon does not seem to be working - not sure at this point whether the rom is too slow (need to try with SRAM but I don't have any right now) or whether I've made a mistake somewhere.
There's no voltage problem - the 28series flash roms are amazing and I use them in everything. No programming voltage needed, they generally work just like SRAMs but with slower write times.rolfmichelsen wrote:You will not be able to write to an EPROM in that way. The EPROMs need a higher programming voltage and signal timings that the Dragon does not provide. You need a proper EPROM programmer to do that. You should be able to write to SRAM connected to the cartridge port.
It is possible for the few Dragon games which are small enough to fit in the 16K (-256 bytes I/O) cartridge ROM address space; but I have always found it to be a very long, boring and unrewarding task (most people don't even bother to post a thank you). I wouldn't be prepared to convert cassette to cartridge (or the other way round) on a regular basis!Rolo wrote: PS: Another idea, that would even be nicer, would be to disassemble cassette tape games, more or less automatically analyze the code, change absolute addresses, if necessary and relocate it to the D32-cartdidge address-range, so that those programs could be on cartridges too. But I still don't know the Dragon well enough to judge, if that would be possible at all or if that is complete nonsense. What's the maximum address-range for cartridges? And what's the size of the average cassette game? And maybe that has also been done before (maybe by some CoCo guy)?
Yep. I think the main part of the problem concerning carts was that comparatively few games were released on cartridges for the Dragon here. Tapes were preferred for some reason. Even the MSX, which enjoyed a huge number of cartridge-based games around the world, seems to have had most of its titles released on tape here.Rolo wrote:Wow, thank you for the response. Seems to be an interesting issueStrange enough, on other platforms you can find a variety of cartridges. For the Dragon I could not find any. And the machine was quite popular in England, wasn't it?
The first breakout board I did seemed to just about work without supports but then I changed to use an attached cable which pulled down on the board just enough to stop some connections working. In retrospect, I should have made my boards fit TRS-80 cartridge cases instead, which would have been a bit smaller.Concerning the PCB. I found an old and unused ISA-formfactor experimental PCB in the basement. I did modify it with as saw, so that it seems to fit well into the cartridge port. Maybe I'll have to sustain it with kind of housing feet or something. That should be fine for a few experiments. Again, I do not have any plans for a semi professional production of cartridges (I don't even know, if that would be legally possible.).
Seems possible enough to me - but maybe not worth the work - doing it on the fly using the Dragon's CPU might be a little slow. People seem relatively happy with loading tape games from MP3 players / phones etc. One thing I did consider was using a cartridge with either an auto-start menu or an extension to BASIC to load .cas files stored on the cart into the areas of memory specified in the .cas header - it'd be like loading from tape but a lot faster. I don't know how some of the preloaders (like Manic Miner) etc. would respond since I never tried it.PS: Another idea, that would even be nicer, would be to disassemble cassette tape games, more or less automatically analyze the code, change absolute addresses, if necessary and relocate it to the D32-cartdidge address-range, so that those programs could be on cartridges too. But I still don't know the Dragon well enough to judge, if that would be possible at all or if that is complete nonsense.