USB Blaster disapears from the hardware setup of the quartus prime programmer when I connect a com port with the teraterm using an FTDI usb to I2C adapter.

@ak6dn: Thanks for your reply. You are right, I should not jump to conclusions. It is not a general problem, just a (common ?) one. Still workarounds 1 and 2 will work, but it may be worth to continue to look for the solution.

Unfortunately, I also have VCP is unchecked already, so that is not the problem.

I use Windows 10 64b.

My FTDI driver has the same version number as yours (2.12.28 from 2017)

My Altera USB-Blaster driver is based on an older FTDI driver (2.12.00 from 2014)

I have the same problem using Terminal software Tera Term VT 4.90 and KiTTY 0.70.0.4, so it seems the terminal problem is not the problem (unless they use the same libraries).

@AEsqu: I think we have the same problem, although for me it is less bothersome.

Not sure why you have trouble to finding the "USB Blaster II", if I Google it, I find, for example:

https://www.digikey.com/products/en?mpart=PL-USB2-BLASTER&v=544

I do not know the device from your link, but would not expect this one will help:

• it seems to be older than the one that we have problems with (it is compared to the parallel port Byte blaster II and only lists older Alter devices in the compatibility list), so it is either on older version of the USB blaster I know, or a copy.
• the factor 10 price difference is interesting, but also suspicious