Retro CPC Dongle – Part 9

OK, so I had a setback. Not a major one, but enough to make me want to go back and redo the design and incorporate all of the learning to date on this project. The key mantra for me is “simplify, simplify, simplify”. If I can do more of the complexity in software rather than hardware without sacrificing the goals of the project, then I’ll do that.

Below is an updated block diagram. Compare this to the original and you’ll see that I’ve simplified the memory interface to connect through an Atmel SAM4S processor. This will handle configuration of the FPGA as well as handling the system storage and pass the data through the support CPU. The system interface (system I/F) will be a fast interface to the internal structures of the FPGA.

Updated Block Diagram

The flash memory is required to be connected to the SAM4S because this will also handle the FPGA configuration through the passive parallel port and needs the storage of the flash device to hold the FPGA images. The MRAM is also connected to the SAM4S as this will be used to manage regular configuration changes and assist with the flash translation layer (FTL).

Moving the storage devices off the FPGA will reduce the number of pins required for connection to the FPGA, making the wiring of this device simpler. I’ve added an ESP32 module from Espressif to handle Bluetooth and Wifi. This won’t be available on the first incarnation of the board, but will be added later as the ESP32 becomes available for sale.

So, same functionality, simplified connections, fewer components.

Watch this space.


Retro CPC Dongle – Part 7

In my last post, I reviewed the board that came back from OSH Park. Within a week I’d also received my stencil from OSH Stencils. Seriously impressive guys! Last time I ordered it took a month to arrive in Australia, this was a week and a half. Not only that, I opted for both the plastic and the stainless steel stencil to compare the fine detail on each. The plastic stencils are fine for larger print, but on my last project, I struggled to get the solder paste to print through the fine 0.4mm holes for the BGA. I may be able to apply more pressure to the steel stencil to get the paste through. Here’s the nice little package from OSH Stencils.

Note the nice little touch with the solder paste spreader and the OSH Stencils sticker for your laptop/bike/pencil case.
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Retro CPC Dongle – Part 6

This picture says it all, my boards are back from the fab lab!


Finished Board (Click for hi-res)


Following on from my last postOSH Park came up with the goods again! Within three weeks of submitting the design, the finished boards were in my eager hands. A quick electrical test and brief inspection under a microscope convinces me these are manufactured to spec.

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