Hi folks!
just a brief update on how this is going ...
It's about two weeks that the QBX board has arrived. The first impression was not so good, as it arrived in a simple antistatic bag as any $2 chinese board would. The only visual difference is the "MENSCH" sticker which seales the bag.
Considering the selling price of about $40 and the historic relevance of this SBC as a 6502 successor and educational value they should have done a better job.
After mounting the board on a breadboard and checking out the monitor and that it was operating, I soldered the missing (and not included) header pins for the J1 and J2 connectors and wired it up with an external 32kB Cypress SRAM:
Power, /CE => A15, DIR => WEB, /OE => GND and the remaining address and data pins.
This configuration worked right from the first power up. No need to enable registers or do other prep work from within the monitor.
After writing some assembler routines, loading and invoking them through the monitor, I got the tone generator working but the waveform is a bit crude resembling what you get out of a 4-bit DAC.
Yesterday I got the UART0 working and tested communication with an Arduino UNO software serial. For later I am planning to connect to a ATTiny85 mcu which I'll to use as a bridge to connect to several I2C devices, starting with a RTC clock module to be able to initialize the current time and date via monitor user command reading from this device.
Regards.
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