Retro CPC Dongle – Part 25

What’s wrong with this picture? (Impedance matching and other things)

It’s about time we talked about high speed signals, impedance matching and signal reflections.  Take a look at this picture:

(Very) close up view of the captured CPC screen

There is something clearly wrong with the image above, the pixels are all there and the colours are almost right, but what you’re seeing above isn’t what was sent from the FPGA. What I think I’m seeing here is signal trace length skew and signal reflections.

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Retro CPC Dongle – Part 23

I unboxed the Terasic DE10-Nano! What a great bit of kit for a bargain price of $130! Nice going Terasic – you build some amazing stuff. I couldn’t buy the components for that price! Here it is, plugged into my development box.

DE10-Nano (Click for Large)

The cables are (anti-clockwise from 11), 5V/2A power from the power brick, USB Blaster connection, Ethernet plugged direct into my dev box (no crossover or switch), FTDI UART console.

There are two images available from the Terasic site, an Ubuntu image with full LXDE GUI, or a console image. I started with the Ubuntu image, just because it had a great ControlPanel App to show linkage to the DE10.

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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 21

Developing a complex embedded system like the CPC2.0 from scratch is a series of massive achievements in miniature, like a nano-scale thunderstorm. Huge steps forward are represented by a signal line going high, or a chip outputting a short sequence of bits, proving the framework of everything built to date. This project is just like that, so it’s tough to explain to people that those few numbers on the screen represent thousands of hours of coding in C, RTL and hardware design to get a coded sequence out of the HDMI chip. There can be a lot of effort behind a blinky LED.

So, to make it a more interesting post, I thought I’d start with this:

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