Designing the Videopac SDCart. Pt.3 Arduino and Videpac data transactions
Introduction In the last post (Pt.2) we got a game from the sdcart transfered to the Videopac. This was done while holding the system in reset while taking over the databus. This worked but I wasn't happy with having 20 I/Os of data, address, and control going through transievers. In this part 3 we switch to having a single 8-bit buffer on the arduino that the vp can access, and let the videopac control the system bus at all time. Less bus-transceivers, allthough I need to store the menu program on ROM and not SD card. We will look at: Bustransciever and control bus activity Find I/O on the cart port for serial tx Prototyping I'm using Sören Gust's ramcart, the aswcurr assembler and sometimes the o2em emulator. My design is partly based on the ramcart (menu rom and game in ram). Prototyping: Videopac, Arduino nano, 74LS245, 74LS00, and Digilent Digital Discovery 2. Preliminary schematic: The atmega328p and the bustransceiver: Serial TX I/O