0
\$\begingroup\$

I designed a board containing a USB to UART bridge in order to program a ATmega microcontroller. I copied the schematic of this breakout board from Sparkfun

https://www.sparkfun.com/products/9716

This is my schematic:

enter image description here

I install FTDI drivers from this link:

http://www.ftdichip.com/Drivers/VCP.htm

in "windows - setup executable". It doesn't work. My computer doesn't recognize it. I have windows 8.1 and I think it could be related. I disabled device driver signatures.

I don't know what to do now. I don't think it's related with my schematic, but I can't solve this problem.

Any idea?

Thank you.

\$\endgroup\$
  • \$\begingroup\$ I'm assuming you got the chip from a reputable dealer? \$\endgroup\$ – Ignacio Vazquez-Abrams Feb 23 '15 at 17:54
  • \$\begingroup\$ Mouser I believe. I didn't assemble the board, but I gave to the manufacturer a bill of materials with Mouser part numbers as reference. \$\endgroup\$ – zapeitor Feb 23 '15 at 18:01
  • \$\begingroup\$ Does it see any new device connected (even not recognized one)? If negative I would assume hardware failure (check voltages, connections etc) \$\endgroup\$ – Eugene Sh. Feb 23 '15 at 18:01
  • 1
    \$\begingroup\$ What exactly does your computer do when it "doesnt recognise it"? \$\endgroup\$ – Grant Feb 23 '15 at 18:01
  • 2
    \$\begingroup\$ With the reset pin floating, I would be surprised if anything happened. \$\endgroup\$ – Matt Young Feb 23 '15 at 18:02
1
\$\begingroup\$

If by "my computer doesnt recognize it" you mean you can't run the exe to install the drivers, you probably have a corrupt download. Download the file again and see if it works.

If you mean the installer worked just fine, but the drivers aren't working properly, then you either hooked it up wrong, have a defective FTDI chip, or have a counterfit chip.

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Hi Grant. I can install the drivers. It says installation was finished correctly. When I plug it in my computer shows a message "USB device not recognized" \$\endgroup\$ – zapeitor Feb 23 '15 at 18:10
1
\$\begingroup\$

The problem is solved. As Eugene Sh suggested, it was a problem with USB lines. I didn't assemble the board so I supossed it was properly soldered, but it wasn't. I fixed one resistor (R4 in my schematic) and now it works fine.

|improve this answer|||||
\$\endgroup\$
0
\$\begingroup\$

Were the D+/D- differential pair laid out on the PCB appropriately? Have you attempted to look at the USB enumeration with a protocol analyzer? I believe for a device to be recognized, all that needs to happen is the 1.5K pull-up is present, so I would lean towards incorrect signaling environment as the culprit.

Also, your schematics don't show an oscillator, but there are pins for an oscillator. While I'm unfamiliar with this exact part, most of the USB device ICs I have used have required a 12/24/48MHz crystal.

|improve this answer|||||
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.