New universal interface

[VELESOFT]

I have in development new interface for ZX Spectrum. PCB size is same as K-MOUSE and on board are CPLD (programmable logic), 1MB static ram (can be with battery backup), 512kB flash eeprom, RTC chip, 2x micro SD slot, joystick port, PS/2 connector for mouse (k-mouse), 8bit stereo D/A sound. Interface will work as DIVIDE with SD cards (DIVMMC) but with reconfigurable memory access... Programmable breakpoints, LIFO memory support, etc...

[radastan]

An Interface 100 times more powerfull than ZX Spectrum itself...

¿Have you think in put a ZX Spectrum FPGA too on it? like Turbo Chameleon 64 for commodore 64, it works as a interface for C64 or like a standalon C64 system.

[VELESOFT]

An Interface 100 times more powerfull than ZX Spectrum itself...

Not true. It's only easy CPLD chip (not FPGA or CPU) and will contain only very easy logic(port decoders, memory paging ports,...).
RTC chip and D/A 8bit convertors are very small,easy and low price components. SD slots must be used for compatibility with DIVIDE (DIVMMC interface also use SD slots http://aticatac.altervista.org/portale/?q=node/15). Price of SRAM 1MB is very very low (lower price than classic sram 512kB). Price of FLASH EEPROM 512kB is also lower than price of 8kB EEPROM and PLCC package size is same, then I use FLASH EEPROM. This is universal PCB and can be used only part of all componnets (without sd slots, without rtc and d/a chips, without k-mouse, etc...).

8bit stereo D/A will compatible with russian ZX software with COVOX support:
http://velesoft.speccy.cz/da_for_zx-cz.htm

RTC chip will supported in ESXDOS and all new files will saved with true date/time.

SRAM will used for divide memory, for ZX rom replacement (some ram pages can be connect instead your ZX rom), etc...
Can be used different types of sram : 256kB, 512kB or 1MB, with 5V or 3.3V supply.

FLASH EEPROM can be used 128kB,256kB or 512kB (5V only). My PROFI interface for ZX128+2 contain same memory capacity (1MB ram + 512kB rom)

[mcleod_ideafix]

I have in development new interface for ZX Spectrum. PCB size is same as K-MOUSE and on board are CPLD (programmable logic)

Which CPLD? (I've seen that some CPLD are even more expensive than small FPGA's):
- CPLD XC95288 (288 bits, 4800 gates, TQ144). 12.42€ http://www.digikey.es/product-detail/en ... -ND/826984
- FPGA XC3S50AN (55296 bits, 50000 gates, TQ144). 8.37€ http://www.digikey.es/product-detail/en ... ND/1756114
(NOTE: The Spartan 3AN series have the configuration ROM included into the FPGA chip)

Will it have a separate CLK line? (it is desirable, as the CLK from the Spectrum is not reliable)

[VELESOFT]

I have in development new interface for ZX Spectrum. PCB size is same as K-MOUSE and on board are CPLD (programmable logic)

Which CPLD? (I've seen that some CPLD are even more expensive than small FPGA's):
- CPLD XC95288 (288 bits, 4800 gates, TQ144). 12.42€ http://www.digikey.es/product-detail/en ... -ND/826984
- FPGA XC3S50AN (55296 bits, 50000 gates, TQ144). 8.37€ http://www.digikey.es/product-detail/en ... ND/1756114
(NOTE: The Spartan 3AN series have the configuration ROM included into the FPGA chip)

Will it have a separate CLK line? (it is desirable, as the CLK from the Spectrum is not reliable)

PCB is designed for XC95144XL or XC95288XL (I plan use XC95288XL - price is about 6 USD).
Yes, CPLD will use own crystal.

Here is example of PCB (unfinished):

[flopping]

Ummmm, very interesting, do you have anything of info to see it?

[mittemot]

lástima que no incorpore también ethernet como el spectranet

[Uto]

Questions:

Are you planning to have a box made for it?

Will it have a reset button? (Spectrum reset)

Why MicroSD and not SD? Why two? I know DIVMMC has two cards, but honestly, I don't know why: you can have all you will ever need for a Spectrum in the smallest SD card you can find, why two? And if you are going for microSD cause there is no room for two SD cards, then definitively I would rather add one SD than two microSDs (microSD cards are not designed to be connected and disconnected many times, and I mean it in terms of comfort, not technicaly, they are difficult to pick, many times you need an adapter to connect to PC, etc.). Also, for the look&feel, specially the feel, I would say a SD card still looks a bit like a floppy disk, while microSD doesn't.

I would even go better for microSD + composite video if room is a problem, than two cards. I think the composite video output from k-mouse interface is a great idea, and I miss it in your design.

Apart of that comment about the microSD cards, the whole PCB looks really interesting. Looking forward to see it finished!!

[VELESOFT]

Questions:

Are you planning to have a box made for it?

Yes, can be. But only some pieces, because for installation to plastic case need some hours.... too much time. But case with signed makrs for drilling can be included.

Will it have a reset button? (Spectrum reset)

Yes, reset and magic(NMI) buttons.

Why MicroSD and not SD? Why two? I know DIVMMC has two cards, but honestly, I don't know why: you can have all you will ever need for a Spectrum in the smallest SD card you can find, why two? And if you are going for microSD cause there is no room for two SD cards, then definitively I would rather add one SD than two microSDs (microSD cards are not designed to be connected and disconnected many times, and I mean it in terms of comfort, not technicaly, they are difficult to pick, many times you need an adapter to connect to PC, etc.). Also, for the look&feel, specially the feel, I would say a SD card still looks a bit like a floppy disk, while microSD doesn't.

SD card slot is too big. During some years will SD format obsolete and hard to buy in shop. Micro SD is more popular and mechanically better (SD card contain also plastic columns between contacts and this columns are very often damaged in card readers). Two micro SD slots are only reserve for future. Can be used or soldered master slot, and second slot can be add in future. I use on PC card reader with micro SD slot, then don't need microsd to SD adapter. Micro SD card is also possible connect without adapter to tablet or phone and share ZX data.

I would even go better for microSD + composite video if room is a problem, than two cards. I think the composite video output from k-mouse interface is a great idea, and I miss it in your design.

VIDEO out from ZX bus work only on ZX Spectrum 16/48/48+, other models have this pins unused or contain different signals. If anyone need video out, I can add on PCB two pins for possibility connect cable with video connector (connector is possible install to plastic case)

[Uto]

Well, I understand now why not SD card, looks fair and logical decisions have been taken. I still think though that wathever other feature that could fit in the same space would be better than a second card slot.

Having two pins to be able to add the video connection on a boxed device sounds nice, and having a box with markings for the drill sounds good enough too (I completely understand it's too much time to mount them all).

If you keep it within reasonable costs, and I see you are going for it, you already have a buyer

[cheveron]

I can understand why you've gone with micro SD, but I'm wondering how hard it would be to support generic USB keyboards and mice without doing a full USB implementation. PS/2 is becoming rarer and there are a limited choice of keyboards and mice but modern USB devices don't usually work with USB to PS/2 converters. I'm also interested to know if the RAM mapped to the ROM page is itself pageable via the 128 paging scheme. That would be very handy for using alternate 32K ROMs such as SE Basic IV. Of course you'd want a 128 version of McLeod_IdeaFix's ULAplus for 80 column mode. The RTC is a nice touch. All in all it looks like a very comprehensive add-on. Does it work when connected behind Spectranet?

[VELESOFT]

I can understand why you've gone with micro SD, but I'm wondering how hard it would be to support generic USB keyboards and mice without doing a full USB implementation. PS/2 is becoming rarer and there are a limited choice of keyboards and mice but modern USB devices don't usually work with USB to PS/2 converters. I'm also interested to know if the RAM mapped to the ROM page is itself pageable via the 128 paging scheme. That would be very handy for using alternate 32K ROMs such as SE Basic IV. Of course you'd want a 128 version of McLeod_IdeaFix's ULAplus for 80 column mode. The RTC is a nice touch. All in all it looks like a very comprehensive add-on. Does it work when connected behind Spectranet?

Can be used PS/2 or USB connector, but only for mouse with PS/2 protocol. I plan place on PCB also small pinhead for extensions. Theoretically can be connect in future new chip with USB mouse protocol...

Interface can work as divide or similar device. Is reconfigurable from ZX. ZX ROM 32kB(on ZX128/+2) or 64kB(on +2A/+3) can be replaced with sram memory with write protect (rom emulation), then you can use own ZX rom.

Interface theoretically can be connect after spectranet, but this device is better connect as master device (first on zx bus). Interface will use 4kB,8kB and 16kB memory paging in low 16kB of adress space. In 4kB mode can work very similar or identically with spectranet. 8kB mode is for divide memory layout, 16kB mode is for MB02 memory paging and ZX rom paging.

[cheveron]

So if I've understood correctly, you could actually run the Spectranet firmware from your interface and have the Spectranet plugged in behind it running passively. Not sure I see the benefit of MB02 paging without also having a DMA. Was there much software written to use it?

[VELESOFT]

So if I've understood correctly, you could actually run the Spectranet firmware from your interface and have the Spectranet plugged in behind it running passively. Not sure I see the benefit of MB02 paging without also having a DMA. Was there much software written to use it?

Interface is in development, all features can be changed in final version. Theoretically yes, Spectranet software can run here, but real spectranet must be also connect. Theoretically....

MB02 paging is here used for allram mode because it's very easy and good. Enable connect 16kB ram pages instead ZX rom and disable or enable writing to low 16kB (rom emulation). For this MB02 mode exist system BS-DOS, and utility for flashing rom 512kB.

For DMA chip exist only some old ZX games with DMA acceleration and some pieces of demos. I plan add easy DMA support to CPLD, if will free space.

[VELESOFT]

Final design of PCB:




PCB is ready for connect two stereo D/A chips (4x 8bit D/A channel or up to 2x 24bit D/A channel). PCB contain only pinhead with sound output - ready for connect small module with sound amplifier/mixer.