USB to multiple TTL serial ports

Hello Pololu,

I am trying to interface multiple TTL-level serial ports (from PICs) to my relatively new pc, that has only USB ports, and no real RS232 ports. Currently I am using a USB to serial cable, and a logic level converter (the pololu serial adapter). I am considering switching to the USB-to-serial adapter, since it has TTL levels as output immediately, and hence one less adapter/converter that can fail. But I will still need one USB port for each TTL serial port…

Now my suggestion is the next: Can’t you combine a USB hub controller chip and several of the USB-to-ttl-serial chips (FT232R, or whatever you guys use), in a single package, so that I can have a single USB connector on one side, and 4, 6 or 8 TX-RX combinations on TTL level on the other side? The idea would be that plugging this thing in would give me a bunch of virtual COM ports, via a single USB cable!

My electronics knowledge and SSOP soldering capabilities are far too limited for considering such a project. But if you guys would create such a thing, you will sell at least one already to me! :slight_smile:

Best regards.


Thanks for the feedback. I think the hub route would be more complicated than necessary. FTDI has some four-UART USB adapters (FT4232H), so you might look around to see if someone already has a carrier or other product based on them.

We are considering making our own USB-serial adapters (using a microcontroller as opposed to one of these dedicated parts), and it looks like we could make 2- or 4-port versions. Would a 2-port unit be interesting to you, or do you really want it to be 4 to be worth it? What if the four-port costs twice as much as the two-port version?

- Jan

Dear Jan,

Thanks for your reply. I didn’t know such chips already existed, and will look for such a carrier board you suggest.

Were you to develop a USB -> multiple TTL serial convertor, I would of course be interested. 2 ports is already a great improvement over a single port, but I think that 4 ports would be more useful, even if then the price might become higher. This would allow me to interface several pics and/or sensors with a pc via a single USB wire, and would allow configurations were I just put my laptop on top of my moving platform, plug in the usb cable, and all is set. And your device would probably be much easier to work with than figuring out how to use this FT4232H chip.

Best regards