FTDI type USB-UART adapter for $3

The USB-UART type adapters have become quite ubiquitous, especially when using the Arduino or its clones. The standard adapter seems to be based on the FT-232RL. Good feature list and reliability. There are others with the PL2303 based chip. But it seems like finding a good driver for these chips is a nightmare. While the FT232RL based solution is great, its cost seems rather steep (about $15) for something that is just a USB-UART bridge.

So how would a USB-UART bridge for about $3 sound???

There is another chip from SI-LABS, out of Austin. The CP2102 is a USB-UART bridge with tons of features (including USB suspend feature). Its footprint however makes it a challenge to solder it. But no problem. That’s what E-Bay is for !!

So here are the steps…

Get a ‘CP2102’ based board from E-Bay. There are lots of them with amazing prices. I bought one for $2.95 shipped!!. Just search for ‘CP2102’ on ebay search. Here’s where i bought mine (Link)

Here it is after i desoldered the male header and soldered in a female header.

20111101-223227.jpg

While these boards are great, the header pin-out (GND,TX,RX,5V,3.3V,RST) does not match the Arduino programming header pinout (DTR, RX, TX, VCC, NC, GND).  Some differences with the arduino are

  • RX and TX ports on the CP2102 need to be swapped.
  • The trace to RST needs to be cut(this RST is related to usb) and re-wired to GND
  • The GND trace on CP2102 needs to be cut and re-wired to the DTR pin (upper left soldered pin J3)
These mods are shown below. The 2 black wires are for the DTR and GND rewiring. The small green ones at the center are for TX and RX swap.

20111101-223245.jpg

Finally i added a new sticky label with the new ports matching the arduino and a heat-shrink sleeve and here’s the final finished $3 USB-UART arduino programming adapter.

20111101-222806.jpg

I tried the adapter out with the arduino OPTI bootloader and it programs correctly!!!

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About

I am a computer engineer living in the beautiful city of Austin,TX. While my day job is designing computer chips, I love to dabble in woodworking, metalworking, r/c and electronics.

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Posted in Electronics
One comment on “FTDI type USB-UART adapter for $3
  1. giltesa says:

    I can not make it work.
    You could put a wiring diagram of the changes or get a better photo? .

    Thank you very much in advance.

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