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blog:initial_version_of_cartridge_pcb_design_-_zikcart_rev1

Initial version of cartridge pcb design - zikcart rev1

This is the initial design for the 'zikcart', a prototype cartridge design for the 'zik80'; notice that the zik80 pinout is more expansive than this cartridge .. this is an easy to use eeprom based card (DIP28), so whatever cpu is being used as the brain can read or write to it. (the AT28C256 32KB eeprom I like to use is a little pricier and getting hard to get, but is really simple and nice to work with; runs at 5V so nice and easy to interface to darned near everything. The cart pinout includes 3.3V and 5V both and allows for (say) up to 1.5MB of ROM space, so is fairly flexible for other parts you could put on there. EPROM, EEPROM, SD card with an interface chip, whatever, should work a treat.

One thing I've probably goofed on is having the top copper pour be GND (just as the bottom is.) The copper pour/fill area is avoiding blank pcb all over - instead filling every available space with copper so it can act as a wick drawing away random signal interference; doing VCC and GND pour pairs can make things nice and clean, but I'm not on top of how the capacitance that would create works. With through-hole parts and top/bottom VCC/GND pours it sure makes it easy to hook power up to all your parts however - no traces needed. Still, this is my first pcb design and I'm allowing for some uncertainties and hoping not too many gross mistakes. Now the waiting game .. 5-7 days promised to manuf the boards, but if theres a sale who knows…

I got into a deal for 10 small boards for $12, which seems about half the normal price. Checking elecrow, seed studio and some others it seems the going rate for 5-10cm^2 boards is about $25 for 5-10 of them. If we call it 10cm-square boards times 10 boards, consider .. it should be easy to make a 5cm-square QFP100 adaptor; put 4 of those onto a 10cm-square board and if you can get 10 of those for $25, thats less than $1 per adaptor; even if you double price to get it FedEx you're less than $1.50/adapter … of course, thats spread across 40 of them, and you probably don't need that many. Ebay the remaining 20 or so off for $20 and you damned near get them for free. (Mind you, once you're confident with your schem and pcb skills, just circumvent the breadboard altogether.. but I rather enjoy the breadboarding experimentation phase.)

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