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Update July 18th

A project log for MSX COMPATIBLE BOARDS FOR RC2014

Create a series of boards designed for the RC2014 bus to achieve MSX/MSX2 compatiblity

dean-nethertonDean Netherton 07/18/2021 at 07:190 Comments

Working on my MSX for RC2014 is not a planned or organised project.  For the most part, when I have some time on the weekends and the occasional evening, I just follow my fancy - would ever takes my interest at the time I sit down.

Sometimes, I just do some research and reading, other times, I might work on a design for a new module or do some software or any number of things. 

The natural result of this, is there a few items in the backlog, at various stages of completion or operation.  

So this journal entry is to briefly note where some of these undertakings are at:

Serial Drivers

On the software front, I have been spending a lot of time trying to get proper serial drivers implemented.  This has required learning the serial driver specifications for MSX (extended bios and fossil).  To test the drivers I have a couple of applications.  A telnet for accessing BBS and a new implementation of a xmodem utility.  It is getting close to be able to make an official release over in the github project.

I certainly have spent far more time on this, than I anticipated would be required - but aint that just usual!

On the hardware front I have got a few things going:

New backplane:

This backplane supports all 80 pins, which includes the 'USERx' lines.  This allows me to avoid having hookup wires between the Memory and PPI modules, making for a clean and simpler install.  Very handy as I often am removing and replacing modules.  

It also aligns with the yellow colour scheme and includes some LEDS to add to the cool factor.  As a kid in the 80s, I always wanted my computer to have lots of leds - but never managed to achieve that goal.  After so many decades that dream is coming a reality!

I think the new backplane show off the kit just nicely:

Fully installed and operational

Cartridge Slot

Another reason for the backplane, was to make it a little easier to incorporate a backplane extension to support MSX cartridges. Its very early days for this module.  I have a PCB made, but have yet to build and test it.  

New Video Module

This one is still in the experimentation stage.  For the current Video board, I am not particularly happy with the quality of the Composite and S-Video outputs.  And the RGB is only just okay.  On the Composite lines, there appears to be quite a bit of noise.

So I have been trying to figure out what is causing the noise and how might I reduce it. This is an area where my skill and knowledge are lacking. 

I have a new experimental PCB design, that incorporates some improvements, including:

  1. Improved layout of analogue and video lines to help reduce interference on the video signals from each other as well as the nearby digital lines.  
  2. Added some filters for the analogue power of the CXA1645 and the V9958 as per the datasheets.
  3. Ability to select different sync types for the RGB output, including TTL level sync.  The TTL level sync allows the video board to drive the low cost ebay arcade RGB to HDMI converters.  The converters are not as good as something like the OSSC - but do produce a very good image for a much cheaper price.
  4. And finally, added a optional headers of the TTL RGB signals so I can more easily hack around with different designs for the converter circuit.


RTC Module

I feel that this module's design is now completed.  I have a working RTC and support for MSX's F4 warm start register.  Once adjusted, using a simple little timing utility - it seems to keep time just fine.

I intend to add this kit to my Tindie store in the near future:

Others

Also on the backlog is the MSX Music module, 3 1/2" Floppy interface, enhanced CPU,  designing 3d printable cases, software enhancements and lots of other ideas.  

Bloody hell, where will I find the TIME for all of this!

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