A big milestone!

A project log for Emulated TMS9918A using RP2040/DVI

An attempt to make an RC2014 module that emulates the TMS chip, with crisp DVI output and some additional RC2014 functionality

shiela-dixonShiela Dixon 09/04/2023 at 12:181 Comment

This isn't just a milestone in this project but a milestone in my life. This isn't the first time that I've ordered a pcb assembled with surface mount parts but it is the first time I've designed a board with an RP2040 and supporting components. My expectations were about 50/50 on whether it would work or not. But as you can see, it does!! Yipeee!

(Try to ignore the ugly through-hole button soldered to surface-mount footprint).

This is really no more than at test to see whether I can put the RP2040 etc onto a board. As discussed in previous logs there is more functionality to add to this project but I didn't think it was sensible to start adding to the logic side at the same time as this big step.

So functionality-wise, this is exactly the same as the 'Feather' version shown previously. Now I have to knuckle down and add that other stuff - jumper for selecting the ports that this appears on and the ability to read the VRAM and all bits of the status register among other things. 

How do I feel about this? I'm chuffed to bits that I've designed my own board with an RP2040 and that it works. This will branch off into other projects.

I have mixed feelings about this particular version of this project. Mainly because we have both surface-mount and through-hole components next to each other, which begs the question: why, if I have resistors, capacitors and ICs surface mounted to this board, are the other through-hole components not surface mount as well? (The answer to that is that the RC2014 itself is a DIY retro computer and the whole point is that it uses through-hole components including DIP ICs. Surface-mount looks out of place.)

There are other issues too - the microUSB port is fine for programming the microcontroller, but it's difficult to plug in a keyboard (with USBA to micro OTG adaptor) at the same time as the HDMI, sorry, DVI socket, because they're too close together. 

In many ways the 'feather' version is great, it addresses many of these issues but it doesn't expose enough GPIO for my next stage. A Pi Pico with DVI 'sock' or other daughterboard would work but would be really ugly (a daughterboard on a daughterboard, and green to boot.)

I do have a plan which I think is a good solution. Stay tuned!


Patrick Dowling wrote 09/05/2023 at 18:36 point

Great stuff. Since I had them lying around I was thinking about using a pico with the DVI sock for the (underutilized) RC2014, but as you say that would be pretty klunky.

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