Retro CPC Dongle – Part 28

As promised in Part 27, I’ve finished a new build of the CPC2 hardware. Here are the board layouts as rendered by OshPark , and if you’re interested, I’ve shared the project.

Top Side
Bottom Side
Four-layer Board

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Retro CPC Dongle – Part 22

The screen shot below says it all. Yay! Video output from the CPC2.0!

Colour test for HDMI output from CPC2.0 board

I promised myself that I wouldn’t post those shaky photos/videos that people seem to post of their game/emulator/screen. Unfortunately, at this time a photo of the screen is the best I can do. Longer term, I’ll get a HDMI capture card from eBay and capture the screens properly, but for now this will have to do as proof of success! Colour bars. Continue reading

Retro CPC Dongle – Part 20.1

I’ve posted the files of my work to date.  They’re rough and will need some work if you want to compile them, but it’s working!

Code is posted on GitHub here.

The support software provides a stdio connection to the Atmel supervisor, allowing me to start working on the connection to the video chip and seeing the results in real time. Stay tuned!

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Retro CPC Dongle – Part 20

Finally, after weeks* of effort I can write about the SPI interface between the Atmel SAM4S supervisor chip and the support CPU in the FPGA. You’ll recall from my last post that I had this working in emulation, but anyone who has worked on FPGAs or RTL code before, a simulation is still a long way from a working configuration. Still, after a bit of work, I managed to get this:

I managed to reliably pass the string ‘ABCD’ (0x41 0x42 0x43 0x44 in hex) across the SPI interface in response to a keypress going from the picocom terminal through the USB serial port of the supervisor chip, passed through the SPI module of the Atmel SAM chip into the FPGA across 4 lines of control and signal, into the soft Z80 CPU. Responding to the incoming data, the software stored in the ‘ROM’ in the supervisor functions would read the transmitted keypress, store it in memory and return ‘ABCD’ across the SPI interface by requesting another transfer from the master. Continue reading

Retro CPC Dongle – Part 19

It’s been 2 months since I wrote about setting up the SPI connection between the supervisor and FPGA. That time hasn’t been idle, but I still don’t quite yet have a proven SPI connection.  What I do have is a Z80 CPU running a program to exercise the SPI connection in a simulation. Valuable lessons were learned along the way that I hope you’ll find useful. Let’s start with a nice picture of the simulation waveforms!

Simulation Waveform, click for bigger image

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