I finally found some time to complete the simplified, low cost offspring of my SDC_One design. Some facts and photos:

SDC_Zero Software-Defined Computer
- a minimalistic 65C02-based computer

Features:
• hardware monitor with single-stepping, disassembly, memory editing and drag-and-drop HEX file loading
• 16 KiB RAM, 64 KiB ROM (easily programmed using h/w monitor)
• terminal (console) interface for 6502
• timer and single LED for 6502
• Power supply, h/w monitor communication and target computer terminal via USB double VCOM device

Assembly time: 30 min

Components - total cost: < 8 USD
• „830” type breadboard
• ca. 40 male-male jumper wires
• one female-male jumper wire
• 1..2 pcs 100 nF through-hole ceramic capacitor
• one 10 kOhm through-hole resistor
• 65C02 CPU
• „BluePill” board (STM32F103C8T6 Minimum Development Board)

Binary form of STM32 firmware available on request

Do you have more about the theory of operation on this?

That's my own design, so I actually have everything regarding the theory and practice. There are also few articles available (3 in English), just google for "SDC_One Software-Defined Computer".

You may also look up my previous posts on SDC_One (dated Jan/Feb 2018) at 6502.org, anycpu.org and retrobrewcomputers forum.

SDC_Zero is a simplified, DIY extremely low-cost version of SDC_One. Another version of SDC_Zero uses the 80C85 or 8085 CPU.
I plan to publish the details at GitHub. Not sure about full firmware sources, as the USB stuff is quite precious. Maybe I'll put the USB core into a binary-only library and the rest (including the CPU logic) will be published in source form.

I would love to try this. Can I use my ST-LINK V2 to load the firmware, and, is there a connection diagram/schematic somewhere, please? Also, is the comparable speed still somewhere in the several hundred kilohertz range?

TIA... Cheerful regards, Mike, K8LH

Description and assembly instructions are attached in .pdf file. Let me know if anything important is missing.

(bump!)