The lash-up I have for tested can be seen below. This implements a working Minima controller with rotary encoder tuning and an OLED display. The keyer paddles and sidetone speaker are enabled by the freeing up of LCD display pins by converting the display to I2C.
Rather than build a controller board, I am laying out an Arduino shield board that will contain the Minima's Si570 and connectors for all the other components such as the encoder, display, CW speed control, paddles, PTT and a myriad of buttons. I have adopted the button logic pioneered by Eldon, WA0UWH. The shield will contain solder pads for an optional second Si570 that could be used for a BFO signal, easily set to be optimum for USB, LSB or CW. Both Si570 devices will have solder pads for a resistive pad to allow easy setting of output level down from the 13 dbm of the Si570. This would allow experimenting with different mixers for example. If no attenuation is desired, a 0 ohm resistor or solder jumper may be installed instead. This also allows for a load resistor to be installed if desired. Here is a quick screenshot of my current (incomplete) state of things:
I am also laying out a PCB for the Minima transceiver module. I have gone back and forth on making it SMT or thru-hole and have decided to use SMT as much as possible. Some of the components will need be thru-hole, but to the degree possible, I will use SMT components. My build will be pretty generic, though I am contemplating using a different crystal filter as I have a module that has been rattling around in my junque box for a number of years that might be fun to use rather than the discrete crystal filter of the Minima. If I do use the filter module, I will attempt to lay it out such that it could be built either way.
Meanwhile, I am collecting parts for the build.