I have the need of a USB-TTL converter cable, but all I have is a USB-FTDI converter cable, that means I have two additional pins (RTS/CTS). If I do not connect RST/CTS pair, will the converter cable act as a USB-TTL converter or won't it work at all ?

USB-TTL cable : https://www.adafruit.com/product/954

USB-FTDI cable : https://www.adafruit.com/products/70


I have the need of a USB-TTL converter cable, but all I have is a USB-FTDI converter cable

FTDI is just the brand of the manufacturer, both cables that you shown do the same thing.

What you describe as USB-FTDI is a USB-TTL converter

The USB TTL Serial cables are a range of USB to serial converter cables which provide connectivity between USB and serial UART interfaces. A range of cables are available offering connectivity at 5V, 3.3V or user specified signal levels with various connector interfaces.

All cables feature an FTDI FT232R device integrated within the cable USB type ‘A’ connector, which provide access to UART Transmit (Tx), Receive (Rx), RTS#, CTS#, VCC (5V) and GND connections. All cables are fully RoHS compliant and are FCC/CE approved.

The use of RTS (Request to Send) and CTS (Clear to Send) handshaking depends on the specific implementation and the way you'll use the cable in your project.


Yes, the two cables do essentially the same job and the FDTI cable should work OK without CTS and RTS being connected (in circumstances where neither end is using them for flow control)

  • \$\begingroup\$ Thanks for you quick answer. In addition to this, could you shortly tell me the main difference between USB signal and serial TTL ? \$\endgroup\$ – Oswin Feb 19 '14 at 9:58
  • \$\begingroup\$ @Oswin: Differences are too numerous to cover here. USB is a highly complex protocol whose specification includes a huge variety of use-cases. Serial-TTL is a very simple very low-level protocol. \$\endgroup\$ – RedGrittyBrick Feb 19 '14 at 10:04
  • \$\begingroup\$ @Oswin That question is like asking "could you shortly tell me the main difference between a motorbike and an aeroplane?" - they both transfer data (move people), otherwise that's about it. \$\endgroup\$ – user253751 Sep 15 '16 at 3:27

I'd connect the RTS and CTS pins together just to be certain.


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