Here is a 5 minute test:
1) purchase your boards in pairs this helps detect same serial number in case of fakes. Any board you buy under $5 is probably a fake, since the bare chip costs ~$4.
2) get your chip serial number, this can be done either by downloading the FT_PROG software or even easier from Device Manager > Ports > USB Serial Port (COMx) > (Right Click) > Properties > Details > Device Instance Path , the Serial Number is in the value after the “+” sign following the PID . For example in screenshot below it is A704DEPPA.
3) google your serial number, those faking the chip are on a tight budget so they have no time to change it, although it is quite possible that some will change it
4) if you find your serial number for example A50285BI is a popular fake, chances are you got a fake
5) Most important: do a favor to the next person and post your serial number in the comments below, in case it is a fake it will appear in Google results for next person getting a fake with same serial #.
Why it is important to spot a fake FTDI fake and why I am posting it ? Because it can ruin your day like it did for me ! Fake FTDI chips are unreliable especially at higher baud rates and you may be pulling your hair troubleshooting your project while the problem is in fact a cheap fake chip.
Hope this helps someone,
How do you test your chips ? Comments are welcome below .