When you need to connect a serial device to a USB port, use this converter cable with the individual lines already broken out. Based on the prolific PL2303TA chip, directly compatible with win XP/VISTA/7/8/8.1 systems and most other OS's.
We often need to access communications ports on various devices, and usually we reach for a TTLyFTDI or similar, but then we still need to find a cable, and add the breakout lines to the unit. For a more portable, flexible solution, we've found these USB breakout cables.
This unit is based on the Prolific PL2303TA IC, which is not quite as popular and established as the FTDI series of USB converters, but we're finding the drivers load up fine on practically all recent OS's. It's a competent chip, creating RS232-like full-duplex communication through a USB bus at 115200 (higher if you don't need real RS232 signalling), and can be programmed to talk at any rate between 75bps and 6Mbps. The PL2303TA is also 3.3~1.8V logic level compatible, and even has an onboard 3.3V regulator you can turn aim at the power rail (dropping it down from the default 5VDC). Handy for powering newer, low-voltage boards!
The cable is broken out at the end to single female pin headers connecting to:
This cable can be modified for 3.3V on the red power line using the ONBOARD 3.3V regulator, which is capable of delivering up to 150mA. Simply move the red power line from the 5V terminal to the 3V3 terminal (see photo). Of course, this voids any warranty, but that shouldn't scare us hacker-types, right?