USB to serial (DE9, often called DB9) — what chip is that?

Just my notes on a small fraction of what’s out there.

Any cheap unit (under about $10) is likely to have a WinChipHead CH340/341 (or whatever it is called), and might work but might not. Mixed results at best. One of these almost bricked one of my machines. Also, even though they are notionally a Prolific copy — in that on Linux you’ll use the pl2303 kernel module as a driver — Linux will often not be able to drive them. Windows seems to do better, because the manufacturer-supplied drivers are better for Win; but still not quite right.

It’s not always easy to know whether a cable will have an original chip in it or a cheap knockoff. I guess if you buy an FTDI-made cable you can be sure it will contain an FTDI chip. I’ve seen a lot of cables advertised as FTDI but the outer mouldings are the same as on the really cheap WinChip cables, and I have my doubts about what’s inside.

Some experts recommend FTDI —

Here is what I found out about some of the infinite number of options.

  1. The really cheap (often blue) no-name ones that are on ebay for like $5. Good luck! It might work, and you’ll save $30+ compared to some options, but it might not; I’ve had limited luck. They have a knock-off of the Prolofic PL2303 — at least, that’s the kernel module that Linux loads (though that does not mean the device will work as you expect).
  2. ATEN UC232A or A1. What’s the chip? Linux driver (see uses the pl2303 module. So that is … Prolific.
  3. Alogic UD29A PL2303 — Prolific (see
  4. CHIPI-X10 — FTDI ( — actual FTDI product, so probably a good bet! (FT231X); also other options too (eg US232R-10-BULK).
  5. Astrotek 205153-D00000 — manufacturer website down. Probably PL2303 or clone.
  6. Klik KU2DB9015 — shops say FTDI, but cannot find manufacturer page. ‘CD’ at has PL2303 and FTDI drivers on it … so probably FTDI.
  7. MCT U232-P9 — this is advertised in some places as FTDI, but a little bit of digging suggests it is Prolific. Some older ones use a Phillips chip. Seems like an old device.
  8. Sunix UTD1009DF — manufacturer says FTDI:
  9. Sunix UTS1009GC is Prolific. So is UTS1009D — varies by model.
  10. Unnamed one from Jaycar — ( Prolific (based on drivers supplied).
  11. CableCreation — seems to do both. Seems too cheap … sold on Amazon, which I try to avoid.

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