The schematic design is very simple and minimal. It contains a cheap USB to serial converter, bought from eBay with less than 2$, a small circuit with three PC-817 optocouplers, RxD/TxD/CW, some current limiting resistors and a bunch of cables and connectors.
All the circuit was built on a small piece of breadboard, 25 x 20 mm, since there was no need to make a PCB for that. The voltage supply for RxD is taken from the USB 5V pin, on the converter.
The male USB and DB-9 sockets were removed from the PCB, so along with the interface breadboard were fitted into a small plastic box, code PP85NC from TME. A scrap USB cable is connecting the interface with the PC, and for the rig, a 4 wires cable with a mini-DIN 8 pins for ACC port and a 3.5 mm jack for CW.
This is the interface all wired up. I had tested it with the FT-817ND at 4800 and 9600 baud rate and all was working ok. Although this circuit can work also with FT-857 and 897, I have never try it.