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C64/SX64 RAM Cartridge (SD2IEC part)

C64/SX64 RAM Cartridge (SD2IEC part)

Sjaak designed and built a C64 RAM/ROM cartridge, which has a 6264 SRAM chip and an Atmel 644.  He did program an Atmega with a Bus Pirate:


Today came in the Atmega644P’s in TQFP package I scored on eBay. Today I’m focusing on the SD2IEC part of the RAM cartridge. I was a bit scary to order them there as ebay is wellknown for knockoffs, nonworking or rebadged stuff. Even the big players will sometimes fall into this trap. However it seems to be working (avrdude is capable of reading the ID and seem to program them correctly) Is it my lucky day?!
When designing this board, which I do usually at night after work, I tend to make little sloppy mistakes (I will write a post about that) and things turn out not as easy after receiving the PCB’s. Notice there aren’t any pins or testpads for an ICSP connection? Because there aren’t any 🙂 I desoldered the Atmega and put it onto an old protoboard I designed ages ago and go my trusty old Bus Pirate out. Programming took ages (a whopping 2097 seconds to write and 2087 seconds to verify) for just a 10k Hex file (I choose to upload only a bootloader), but seems to be programming the chip ok. Next I also programmed the fuses. and prepared a microsd card with the SD2IEC firmware on it and stick it into the memory card holder.

Project info at