The Select Mini uses a ESP8266EX WiFi chip for the wireless connectivity.
The ESP8266EX runs the UI and Web Server whereas STM32F103C8T6 chip on the mainboard handles the motion controller
(discontinued as of roughly middle of August 2016)
From printer received May 27, 2016
(middle of August 2016 - present)
From printer received September 2, 2016
The first few batches of Select Mini's had an issue with the control dial. A UI Controller firmware update in June added some debouncing code to help but it did not completely eliminate the problem.
The newer version of the UI Controller board added a 74HC14 Hex Inverting Schmitt Trigger. This was added to enhance signal condition for control dial. The updated UI Controller boards started shipping sometime in August. The update made a noticeable difference while using the control dial. No more or at least reduced skipping back or jumpiness while cycling through the LCD menu. Complaints are still made even with the newer boards.