Build your own USB to Serial dongle

[Johan von Konow] found that he was using an FTDI USB-to-Serial chip in a lot of his projects and wanted to have an easy prototyping component on hand to facilitate this. What he came up with is the extremely small USB to serial dongle seen above. The copper fingers are designed to plug into your USB port. And if you’ve got an unused thumb drive (we’ve got a 128mb version that’s been collecting dust for years) it would make a perfect enclosure for the device.

He’s using an FT232BL chip in a LQFP-32 package. That’s got 0.8mm pitch so make sure you’ve got a steady hand, a fine tipped soldering iron, and some solder wick on hand. The 0603 passives might also give you a bit of a run-around during soldering, but all-in-all we think everyone will be able to successfully assemble this with a little bit of practice. The chip is the most expensive component at just under $6. But the good news is that the board is single sided and only needs one jumper wire making for very little drilling and easy home fabrication.

If you’re putting in a parts order, we’d recommend getting doubling the amount of resistors and capacitors. Chances are you’ll drop a few and nary will they be seen again. We also highly recommend looking into [Gerrit's] surface mount component clamp.

21 thoughts on “Build your own USB to Serial dongle

  1. And those looking into a truly minimalistic (not necessarily the best or the fastest) solution should look into AVR-CDC project, which is based on V-USB library. Actually even the crystal is not going to be necessary.

      1. I ordered some cp2102 based usbtty dongles @ ebay from a guy called sinedy for £2.80 and free shipping, go get them!

  2. Just as a point of clarification, this is TTL Serial not RS232 Serial. If you were hoping for a DIY replacement to hook up to that old hardware this isn’t it. I was hoping the guy had come up with a good replacement for those USB->DB9-RS232 adapters that always seem to suck.

    Tidy little board ya got there though.

    1. Just add an 232 based chip to the other side and you have it. The FT232R chip doesn’t require an external crystal and offers the same options so you can look that up too. Those usb to db9 converters use a pin compatible chip from prolific.

    2. Ah, that clears it up. I was wondering how these differ from RS232. A USB-DB9/RS232 is exactly what I was looking for. Thanks for this comment.

    1. I don’t remember the exact price I paid, but I can assure you that they were well below one dollar (in china).
      Sill you got a point, you don’t build an adapter to save cost. I use it as a base for future projects. Since the PCB is single sided I can place a microprocessor on the backside to have a miniature platform that can be used for all kinds of projects. Next up is a miniature USB controlled 433MHz radio transmitter…

  3. 3to5 dollar nokia usb cables on ebay have the same ftdi chip (or the prolific equivalent) in a neater board. Just Saying.

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