I have completed (as far as I went) the build of my Minima Controller Shield, but have yet to complete testing of the board. I populated only a single Si570, the edge and ICSP stackable headers and the header for my OLED display.
The prototype board needs a little work. I need to move the VFO SMA edge connector away from the USB connector. This will work for a prototype, but needs to move in the final version for sure.
The OLED display is a 3V3 device and I have it sharing the same I2C bus as the first Si570 for the VFO. There is also a 5V set of connections for an LCD display with an I2C backpack for example. This shares the same I2C bus as the PCA9546 multiplexer input, so it should allow 5V displays to work without driver modifications. I will need to customize the 3V3 OLED driver to take into account that it is connected to the PCA9546 multiplexer. I used this device because it allows voltage level conversion with a 5V input side and four 1.8 - 5V or more output side I2C buses. It also allows me to address multiple devices that do not allow you to change their I2C address such as the Si570. Without it, one would be limited to a single Si570 on a bus.
Ok, off to do some voltage testing and then to see if I can address the PCA9546. If so, I will get busy on my display driver changes and testing the Si570. I plan to roll my changes back into my Si570 driver to allow multiple instances behind a multiplexer as a compile time option.