When you try to upload the firmware, is OpenSprinkler in bootloading mode? As I said earlier in the thread, if you already know you have OpenSprinkler 2.1, there is no need to click on ‘Auto Detect’. In any case, before uploading firmware, make sure OpenSprinkler is in bootloading mode.
Once it’s in bootloading mode, Windows should detect it as a device under libusb-win32 section, and the name of the device is USBasp.
Also, make sure that when you enter bootloading mode, do NOT press the button for too long. If the button is not release within 1-2 second, Windows thinks that the device has lost response.