The Breadboard-2 design was created to make development of software for a STM32 microcontroller as simple as possible. The design goals were:
- Serve as a "reference design" for a decoder such that other designs could largely be done by omitting unnecessary elements and selecting new components.
- Fit a standard 400 or 830 tie point breadboard.
- Have a connector for a SW programmer.
- Operate over the full range of NMRA voltages to be scale independent.
- Have an easy to understand schmatic, suitable for teaching and that can be used as a basis for scale-specific decoders.
- Have an easy to understand PCB, suitable for teaching.
- Use low cost, over-specd, highly available, and easy to replace components.
- Include serial output capabilities for debugging.
Actual size: 2" wide x 3" tall (not counting headers at top).
It is expected that most users will connect the SW PROG and Serial headers to use the board for software development activities. Users who do not need external components (e.g. motors, or external function devices) can simply solder power wires to the RL and RR inputs. Users who want to connect external devices would likely populate J1 and J2 and plug the board into a standard 400 or 830 point breadboard. The exposed connections allow testing things like grain-of-wheat bulbs for lighting effects.
Although this decoder is not specifically intended to go in a locomotive it could be installed in one. This may be particularly useful when developing motor control code.
View the Breadboard-2.pdf schematic without having to open KiCad!
The document CALCULATIONS.xlsx contains a worksheet for each schematic block with all of the relevant calculations.