SPI port is not exposed to the external pins in MicroView. The SPI Interface is dedicated to the OLED display and not shared. This is a real shame. There are many devices that use the SPI interface such as SD Memory, Ethernet, RFID Chip readers, etc, just to name a few. These are not commonly supported by other interfaces such as serial and I2C.
If there is a way to bring out the SPI interface, this would be a major improvement.
I would see a real value in a “MiniView” that had a bit larger OLED display, with six extra pins – the four SPI pins MISO, MOSI, SCLK, chip select SS plus two more chip select lines SS2 and SS3 for other devices.
If you plan hack your MicroView to attach other SPI slave devices to the pads for pins 11, 12 and 13, to control them alongside the display, make sure your sketch at least does a uView.begin() before communicating with these devices. If you don’t there’s a possibility that you could damage the display. Also, it would be best to disable the SPI interface and set pins 11 and 13 low whenever you’re not sending or receiving. And, don’t do a uView.end() while you’ve got SPI enabled.
SS is dedicated to selecting the display so bringing it out would be of no benefit. You can use any other I/O pins as SS lines for other devices.