I designed a small board that needed the capability of communicating over USART, so I threw in an FT230XS USB|USART Bridge. The device use is so simple that I am out of ideas for troubleshooting.

Looking over the datasheet we can find a suggested bus-powered configuration enter image description here

I placed the device on my board exactly as they have don here, minus some of the bus filtering enter image description here

I have measured connectivity between the USB side and the 27R resistor, as well as the FT230Xs side and the 27R resistor. I also get all the expected voltages around the device, including the 3.3V output shown in the diagram below. Everything is as expected, it's just that nothing actually happens when I plug the device into a usb port.

I have tried plugging the device into both a Win8 machine and a linux box, but nothing happens. Both machines have the appropriate drivers installed to my knowledge.

The interesting thing here, though, is that no only do the devices not attempt enumeration with the usb stack of the host machine, but they do not do anything. I put a scope on either side of the 27R resistor and no data appears to be going through. Namely, the FTDI chip is not attempting to identify itself on powerup, so the host machine obviously is not aware of anything having been hot-plugged.

Is there anything immediately wrong with the design? Are there some additional steps to getting the FT chips to work? After the first FT chip would not enumerate I figured I may have damaged it at some point. Since I ordered three it was no big deal. I used my heat gun to remove the first and solder the second. Again, the second chip demonstrated the same behavior (or lack there of). I then went on to change out the chip a third time, but once again nothing is working.

  • \$\begingroup\$ That USB micro-B connector seems a little strange to me. It should have 5 pins in this order: 1 VBUS, 2 D-, 3 D+, 4 ID, 5 GND + the shield pins.. \$\endgroup\$ – m.Alin Aug 20 '15 at 9:23
  • \$\begingroup\$ @m.Alin, the footprint I used does have 5 pads, but the ID pin is not connected to anything. \$\endgroup\$ – sherrellbc Aug 20 '15 at 9:33
  • \$\begingroup\$ So don't you use ferrite bead and capacitor for filtering? I think that is the problem. The other thing is C8 should 100nF. \$\endgroup\$ – Oka Aug 20 '15 at 9:36
  • \$\begingroup\$ @Oka, I would consider these as issues as well, but the FT chip never drivers D+ or D- at all on powerup. The only output I am getting from the chip is the 3.3V. \$\endgroup\$ – sherrellbc Aug 20 '15 at 9:40
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    \$\begingroup\$ I did what you did, the same design, but I got what you got :) . after checking the datasheet, I found that the footprint was wrong i.e I created QFN footprint on SSOP footprint so the the pin order was wrong. check this, it might useful. \$\endgroup\$ – abdullah May 23 '17 at 21:09

Try to make an external pullup for D+ (1.5 kOhm, to the 3V3OUT pin). Maybe the problem is in internal pullup.


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