ECU Cable
An inexpensive VAG-COM FT232RL cable can be used as the hardware interface between your laptop and the ECU. Make sure the cable you buy has an FT232RL chip made by FTDI.
Drivers - https://www.ftdichip.com/Drivers/D2XX.htm
OBD ECU Reflash Cable
https://www.ebay.com/itm/284964724223
Note - Some cars only came with a BMW 20 pin DLC connector under the hood and did not have a 16 pin OBD connector under the dash. If so, buy an additional BMW (20 pin) to OBD (16 pin) adapter.
BMW to OBD adapter
https://www.amazon.com/s?k=BMW+OBD+20+pin+adapter+to+OBD+16+pin
INPA (+all EDIABAS BMW software) require a separate signal to detect the battery and ignition. Some cables need to be modified to provide this information back to the calling application. K-DCAN cable will work out of the box for both reflashing and diagnosing via EDIABAS BMW software. VAG-COM cable needs to be modified.
FTDI USB Drivers - https://www.ftdichip.com/Drivers/D2XX.htm
* Use MS41 ECU Portal for easy install. Right-Click "Help => Install FTDI USB Drivers"