DUO Tiny – pocket computer

Construction based on Jack Eisenmann’s DUO Tiny. Whole computer fits into credit card sized sweet box. This AVR microcontroller based device can be programmed in custom made DTPL language. Four keys keyboard was designed for coding on DUO Tiny.Preparing hardware to work was divided in two steps. First loading “empty” DUOtiny base (bootloader). Next loading sample code (programs). Loading bootloader via (special sketch programmed) Arduino UNO was ugly for me. Thus I was adding regular, 6 pin AVR ISP connector (and removed left 4_PIN connector). Loading programs must be done by (special sketch programmed) Arduino using seriall port like emulation on 3+1_PIN connector. In real world this is also an alternative for tiny keyboard… I was drawing regular schematic based on website photos and informations. Pins on scematic was named (…_A ##)  according to connection with specific Arduino UNO pins.I was used SMD as discrette elements in this construction. Is this possible to replace microcontroller and memory for SMD too. Thin wire soldering was enough for prototype board.DUO Tiny is not so easy for programming – keyboard is “basic” and DTPL flow documentation is sometimes not clear. But, in general construction is great for research and learning “how and why” small OS and DTPL language work. Main system was written as Arduino sketch – in C like language.
Now I am thinking about some improvements: speeding up internal uC clock, programming externall pin output (good for test like blinking LED), using regular RS-232 connection for programming without Arduino and even full sized keyboard connection…