• Please review our updated Terms and Rules here

Sanyo MBC Alive with USB keyboard

J

joezilla

Member
Joined
Sep 11, 2024
Messages
28
Location
New Jersey, USA
Here's my triple five. Near and dear to me, this was the first computer I ever owned. A colleague of my dad's had three of them and gave me one, maybe in around '87. I'd say it's the machine that got me excited about computers and programming and started my career in the field.

Sadly my original machine isn't around anymore, but I managed to get my hands on a basically unused machine last year (like squeaky clean). Unfortunately, it didn't have a keyboard, but with a little coding and an Arduino, that was a quick solve. If anyone needs the library that translates from a PS/2 or USB keyboard to the Sanyo's proprietary serial keyboard protocol, well, here it is: https://github.com/joezilla/sanyombc-keyboard

And yes, I put a Gotek in the unused slot :)

IMG_3582.jpg
 
I have all the usual from back in the days - Wordstar, GW Basic, Turbo Pascal. And copies of Dos 1.25 and 2.11. I have little in terms of games, to be honest, and since machine is a DOS machine and has no compatibility with the XT in terms of graphics, it's hard to find things that work. I unfortunately don't have the optional CGA card, and it's impossible to find so far.

P.S. Since you're the leaded solder guy - I'm using your graphics adapter from your blog :)
 
The CGA card would be a great get. Glad the adapter is working out for you! I hope to have a cooler version down the line.

Also glad to hear Turbo Pascal works well. Do you have a serial card?
 
I don't have the serial card. Turbo Pascal 3 works well, yes (not enough RAM for 4 though). That was the second language I learned after Basic, on the 555.
 
Last summer, I was trying to make a serial card from the available schematics, although I haven't gotten it to actually work yet.

That is likely to be my oddball serial configuration, or the Kermit port not working 100%, or some combination thereof. Mostly it's because it's been sitting on the shelves waiting for me to take some time to work on it.
 
seat safety switch said:
Last summer, I was trying to make a serial card from the available schematics, although I haven't gotten it to actually work yet.

That is likely to be my oddball serial configuration, or the Kermit port not working 100%, or some combination thereof. Mostly it's because it's been sitting on the shelves waiting for me to take some time to work on it.
Click to expand...
Did you ever finish designing and testing this? The SAMS schematic looks really wrong as it has the RXC (receive clock) shown as an 8251 output to the line driver but that pin 25 is a input to the 8251.

To run TXC and RXC baud at the same rate (only choice if using the single line 15 from 8253 as baud source as intended) from the 8253 pin 15 of the header should drive both pin 9 and 25 as inputs to the 8251. Being the MBC is supposed to a PC and presumably communicate with PCs and PC peripherals the RS232 should be setup for asynchronous mode anyway like a PC. (no TXC/RXC on the DB25).

Either way the SAMS is slightly wrong. For synchronous you'd still drive line driver to RS232 pins 15 and 17 from the header pin 15 directly that would also input to RXC pin 25 and TXC pin 9 of the 8251. Pin 25 of the 8251 is an input. As originally presented in SAMS it will never work as your RX clock/baud would be stuck forever at 0. Quick fix on a built board like this just jumper 8251 pin 9 to 25.

1000037032.jpg

This one from Soft Sector Nov 86 is what youd want for PC style asynchronous RS232. Pretty much the same thing but cleaner. Pins 15 and 17 arent even populated or connected in most PC cables and devices. I suppose above wouldnt hurt with the green line modification but youll never use synchronous mode in the PC world which uses 8250 and 16550 devices.

1000037030.jpg
Mind that 26 VCC is NOT connected to 9 and 25.
 
Last edited:
I also just noticed SAMS incorrectly has DTR going to pin 21 instead of 20. 😆
 
Thanks for that reply, because that was almost certainly (one of) my many problems here.

I should probably be building this from the datasheets. It looks like I did at least consult it for the symbol, as the NEC datasheet says ~DTR is on pin 24.

I'll take a look at the Soft Sector schematic and make some changes, thank you again

Screenshot 2026-08-31 at 1.43.53 PM.png
 
~DTR is 24 on the 8251 but SAMS has the 1488 ~DTR output going to DB25 pin 21 when it should be pin 20 on the cable. That and a missing connection between 8251 pin 9 and 25 to resulting in no RX clock. Those are the two blatant errors in the SAMS schematic. Whether you drive 15 and 17 with clocks on the cable or not is inconsequential because youll always be using async mode and any PC RS232 devices are going to ignore or NC those.

I bet you could get it running with a wire from 9 to 25 to complete the clock circuit and swap the connection for ~DTR outout on DB25 from 21 to 20. Though youre probably aware its TX only in your setup, so in that case the other side wasn't getting ~DTR (pin 21 is a loopback/test terminal not ~DTR).
 
Last edited:
Yes, if memory serves, TxD and RxD were oscillating in a loopback, but I was getting nothing even with flow control turned off on Kermit. No RX clock would certainly impede things...
 
RxD doesn't appear connected to the 1489 in your pic? Could just be the way the schematic is drawn.
 
Yeah, it was connected through a label. That's just a small portion of the old schematic – I just went ahead and updated from the Soft Sector illustration, but first I want to try connecting the RXC and TXC pins on my test board before I order. Might be a few days, the Sanyo is really deep in the storage stack!
 
You must log in or register to reply here.
Back
Top