Here’s what you actually need to know: CSR (Cambridge Silicon Radio) was a major Bluetooth chip manufacturer. They were acquired by Qualcomm . “CSR 4.0” usually refers to a Bluetooth 4.0 adapter using a CSR8510 chip (very common in cheap USB dongles).

I understand you're looking for a — but I need to give you a proper, safe, and effective piece of guidance first, because “CSR 4.0” can be misleading or risky if downloaded from random driver websites.