Take one PL-2303 USB-serial cable (e.g. USB to UART (TTL) Cable module PL2303 Converter | eBay) - £2.99
One 2m RJ45 ethernet cable (e.g. 2m BLACK RJ45 CAT5 PATCH ETHERNET NETWORK CABLE LEAD | eBay) - £0.99
Remove one end of the ethernet cable and strip back, check wiring colours.
The USB serial converter has a small circuit inside:
As a side note, the little PCBs are great for mods that need a serial interface such as webcam long exposure mods or DSLR shutter cables. The DTR and RTS si