FTDI were once the interface of choice and perhaps the most common. But
there's a story behind that : they didn't like other manufacturers cloning
them and issued a windows driver that sometimes destroyed devices. This had
the effect of people avoiding anything identified as FTDI in case it turned
out to be a clone. FTDI pulled back and stopped destroying them (instead
merely warning) but the drivers were out there and the reputational damage
was done.

I don't know if they got their pole position back. I don't think so. As a
designer, I still consider them good products. As a customer, I'm wary.

I think the most common on new designs - especially on cheap devices - is
the CH340 and relatives. Of course, most new designs integrate the USB
interface and don't have a chip at all. But that's only based on what comes
in my aliexpress parcels, not any industry stats. I think the CH340 can
also have polarity flipped programmatically.



On Tue, Jan 13, 2026 at 2:36 PM Tom Katt <[email protected]> wrote:

>
>
> On Tuesday, January 13, 2026 at 9:19:25 AM UTC-5 Adrian Godwin wrote:
>
> Some RS232 converters are biased to accept TTL, and some USB-serial
> adapters can have inverted data. It's a bodge, but can simplify a board
> made for a specific purpose like these.
>
>
> Yeah - I took a crash course on the various flavors of serial when I
> started working with the Noritake display...  While *most* devices will
> work with TTL, the bipolar voltages of 'true' RS232 mean that sometimes the
> TTL signals from many usb adapters is seen to be inverted...  After a lot
> of poking around I discovered that FTDI - who is the most prevalent usb
> serial chipset - has a configuration program that allows you to invert any
> pin you want.  That allows common cheap usb adapters to work.  But
> controller projects will need an inexpensive MAX232 adapter to create the
> 'correct' voltages.
>
> If you ever need it, you can download the FT_PROG configuration app from
> the FTDI website <https://ftdichip.com/utilities/>.
>
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