Long story short, my phone messed up and it's stuck in a bootloop. The phone in question is a Coolpad 7560U, also known as Orange Nivo, running Android 4.1.2 Jelly Bean. Data and cache wiping do not fix the bootloop. USB jigs are not a valid method either. The usual means of connecting to it using adb or fastboot don't work anymore -- neither will detect the phone in any way. I have tried all of the power on button combinations. All I can manage is to get into the stock recovery mode (the same one the bootloop passes through) and a QPST "通讯中 Secboot" Download mode.
I am connecting the phone to my Windows 8 x86 PC through an USB cable. For a certain timespan during the boot loop, the following devices show up in Device Manager, all at once:
- 3 storage devices : One of them is a CD-ROM drive and the other two are generic removables - None of them are accessible, returning the prompt "Please insert a disk into drive *:".
- 4 other devices:
Under "Ports (COM & LPT)"
Coolpad Android AT USB VCOM (COM7)
Coolpad Android Diagnostics USB VCOM (COM10)
Coolpad Android NMEA USB VCOM (COM9)
Coolpad Mobile USB Modem Phone
These four seem like my only means of landing a connection to the phone.
Update: According to Alex P.'s answer, I can confirm that the "Secboot" mode puts the phone into a QPST Download mode. The 4 serial port devices do indeed allow for access to the phone through Qualcomm's QPST software suite, and probably impossible to push adb or fastboot commands through.