Introducing: Dragon multi-cartridge for roms
Posted: Sun Jun 23, 2013 7:50 pm
Hi guys,
I just wanted to show you the just finished prototype of my Dragon multi-cartridge (we were discussing it a few month ago).
You'll probably won't like the design, because it's plain green, but that was the cheapest solution (and a can of paint is easy to obtain). And back in the day PCBs were brown or green, sometimes blue.
The board can be populated with 27(C)256 or 72(C)512 EPROMS and is therefore offering 16 or 32 8k game slots.The slots are selected by a combination of an hexadecimal rotary switch (slot 0 to 15) and an additional simple switch (slot 16 to 31) in case of the 72(C)512 EPROMS. The EPROM type is defined by setting two jumpers on the board.
It looks like that:
And the solder side: Most of the cartridges seemed to be 8k, so I did not bother to also implement 4k banks. In that case I simply waste the upper 4k .
I tried the ROM-images of the download section of the archive like Berserk, Metioroids, Cave Hunter, Diagnostic, Edit+, Dasm Demon... and, that's funny, even Color Backgammon of the Tandy section. They're all working fine!
Question to the Dragon-specialists: Does anybody have a listing of all the Dragon-compatible Tandy cartridges? Was Color Backgammon just a lucky draw or are most of the ROMs working?
What is still missing? Well, it's a prototype and not perfect:
1. No housing and the board is quite heavy. The form factor was dictated by the layout program and the price scheme of the PCB maker. And I never had a Dragon cartridge. So I do have no sample.
Solution: I'm going to mount the PCB on an aluminum plate with spacers in between. That worked perfectly with the LAFUMAT disk controller: 2. The cartridge is almost swallowed by the giant cartridge bay of the Dragon and the rotary switch is right at the edge of the housing. I did underestimate this, when I designed the board. It takes very tall and slim fingers or a small screw driver for turning the rotary switch, when the cartridge is attached.
Solution: Hmm, there is no simple solution. Using a screwdriver, pulling the cartridge, selecting and reinserting, or redesigning part of the board (quite some work: its crowded and only two layered) 3. Minor PCB errors: one line is missing, two vias were not drilled (edge connector, Q<->CART, GND<->GND), I forgot 4 resistors, some labels on the silk layer are not accurate.
Solution: Those are easy to repair manually. At the moment I have 10 PCBs on my desk. I've already changed the design-files. So, if there ever will be another PCB order, those flaws will be gone.
That's all for tonight!
Regards!
I just wanted to show you the just finished prototype of my Dragon multi-cartridge (we were discussing it a few month ago).
You'll probably won't like the design, because it's plain green, but that was the cheapest solution (and a can of paint is easy to obtain). And back in the day PCBs were brown or green, sometimes blue.
The board can be populated with 27(C)256 or 72(C)512 EPROMS and is therefore offering 16 or 32 8k game slots.The slots are selected by a combination of an hexadecimal rotary switch (slot 0 to 15) and an additional simple switch (slot 16 to 31) in case of the 72(C)512 EPROMS. The EPROM type is defined by setting two jumpers on the board.
It looks like that:
And the solder side: Most of the cartridges seemed to be 8k, so I did not bother to also implement 4k banks. In that case I simply waste the upper 4k .
I tried the ROM-images of the download section of the archive like Berserk, Metioroids, Cave Hunter, Diagnostic, Edit+, Dasm Demon... and, that's funny, even Color Backgammon of the Tandy section. They're all working fine!
Question to the Dragon-specialists: Does anybody have a listing of all the Dragon-compatible Tandy cartridges? Was Color Backgammon just a lucky draw or are most of the ROMs working?
What is still missing? Well, it's a prototype and not perfect:
1. No housing and the board is quite heavy. The form factor was dictated by the layout program and the price scheme of the PCB maker. And I never had a Dragon cartridge. So I do have no sample.
Solution: I'm going to mount the PCB on an aluminum plate with spacers in between. That worked perfectly with the LAFUMAT disk controller: 2. The cartridge is almost swallowed by the giant cartridge bay of the Dragon and the rotary switch is right at the edge of the housing. I did underestimate this, when I designed the board. It takes very tall and slim fingers or a small screw driver for turning the rotary switch, when the cartridge is attached.
Solution: Hmm, there is no simple solution. Using a screwdriver, pulling the cartridge, selecting and reinserting, or redesigning part of the board (quite some work: its crowded and only two layered) 3. Minor PCB errors: one line is missing, two vias were not drilled (edge connector, Q<->CART, GND<->GND), I forgot 4 resistors, some labels on the silk layer are not accurate.
Solution: Those are easy to repair manually. At the moment I have 10 PCBs on my desk. I've already changed the design-files. So, if there ever will be another PCB order, those flaws will be gone.
That's all for tonight!
Regards!