Ktoid, a modified K80W for Altoid can

[Bill Shen]

Paul DB suggested another Altoid design but this time based on K80W.  It is called Ktoid.  This is K80W trimmed down to fit an Altoids can; on-board CF interface is replaced with plug-in SD card, so is the on-board RTC replaced with plug-in RTC module.  It is still a through-hole design in 4-layer pc board that barely fit.  It should run RomWBW but I can't test it yet because I'm waiting on the 32-pin PLCC socket for the 512K EPROM.
Bill

[Paul dB]

Wow, that's a snug fit! Bill, it must be frustrating not having that last component yet, the 32-pin PLCC, to verify construction.

I'm tempted to ask you for the Gerbers even if the board is untested as is. Nice thing with HTH construction is that it's always easy to reuse the chips for the next revision ;-) 

Thanks,

Paul

[Bill Shen]

Hi Paul,
Here are schematic and gerber photoplots of rev0 Ktoid design.  Let me know if you've decided to order the pc boards, then I can send you pictorial assembly guide which are series of photos showing how the board is assembled step by step.
I should receive the PLCC32 fairly soon, probably this week.  I can also program the CPLD to do serial bootstrap without EPROM which is probably what I'll do while waiting for the PLCC32 socket.  This way I can run basic diagnostics to check out the hardware.
Bill

[Paul dB]

Boards ordered :D (You didn't really think I could wait, did you? Ha!)

Please do send the assembly guide.

Thanks,

Paul

[Bill Shen]

OK, here are the pictorial assembly guide.  Resistors first, then capacitors, then the rest.  All design info will be uploaded to github, but I'm not proficient with github, so it'll take some times.
Bill

[Bill Shen]

Annotated Ktoid.  Bill

On Tuesday, June 23, 2026 at 12:44:16 PM UTC-6 Paul dB wrote:

[Paul dB]

Thanks for sharing detailed photos, Bill. Good to have as reference when building the board.

Regarding github, I've stumbled along myself when I attempted to set up one for RomWBW. There are lots of tutorials available on the net, but the ones I tried all seemed to diverge in one detail or another, eventually leading me into the rabbit hole. Hmm, why does that remind me of Colossal Cave Adventure?

Anyway, I hope you have better luck with github.

Thanks again,

Paul

[Bill Shen]

The PLCC32 sockets didn't show up so I'm going ahead with testing of the Ktoid without the flash.  First, the NOP test with just Z80 and 7.37MHz oscillator by grounding all data lines through 4.7K resistors.  It worked.  Then added a CPLD that drove the data lines to ground instead of pull down with resistors, that also worked.  Now I'm adding a small 32-byte ROM and a serial port in CPLD.  The idea is to boot with CPLD ROM that loads 256 bytes of incoming serial data into RAM then jumps to RAM to execute the uploaded program.  The CPLD design fitted OK in an EPM7064SLC44.  I'll run tests tomorrow. 
To be continued...

[Bill Shen]

Still have not received the PLCC32 socket, but making good progress with board testing by bootstrapping from CPLD.  The serial bootstrap code is quite small, 15 bytes, but enough to serially load 256-byte program into RAM then execute the program in RAM.  RAM is now populated and system clock is changed to 22MHz.  So far it is working with simple diagnostic programs.  Next step is to populate the KIO and test it.
Bill