Alpha version (Prototype)
Its divided into two cards.
Dragon Memory Card
This card contains a Dual Port SDRAM Chip connected directly to Dragon Computer expansion bus. And can accessed directy from Dragon Computer from address $C000.
USB Data Transferd Card
This card contains ATMEGA8515 microcontroller and Latch 74HC573 for attach DP-SRAM as a external microcontroller RAM.
This version serial works at 300 baud.
Beta version (Manufactured PCB)
The first single PCB board that contains all Memory+Data transferer. PCB are manufactured by PCBWay and designed with KiCAD.
Firsts test are go well, but I needed ajust SUT_CKSEL to Ext. Crystal/Resonator High Freq; Start-up time: 16K CK + 4ms and activate BODEN and CKOPT. (FUSES: 0xC1, 0xAF). This is a important note because other timming configuration not works very fine with this type of external RAM.
Finally adjusts serial speed to 9600 baud.
Tomeu Capó
Ted Fried
Keith
Stephen Moody
Jac Goudsmit