I found out that adb stops recognizing the Clover Mini after the Semi-Integration driver is installed.
I did the following to remedy the situation:
- Open Device Manager
- Select "Clover Devices"->"Clover Mini Merchant mode" and open the properties dialog
- Select "Driver"->"Update Driver..."
- Select "Browse my computer for driver software"
- Select "Let me pick from..."
- Select "ADB Device" and click "Next"
- The Clover Mini is now shown at "Universal Serial Bus devices" as C300 and the adb can recognize it