Cannot connect 3pi to computer

I am the president of the robotics club at my school, and we have come across a problem which I think maybe due to a driver.
We have one laptop running(all of our computers are windows 7) , and on any of the other laptops, our attempts to install the appropriate software to program and debug our 3pi’s has failed.

Ive seen similar posts to this, but they did not seem to help.

No matter what we do, we cannot seem to get the robot to be read by the computer. Ive looked at the one working laptop, and tried to mimic things as closely as possible.

When I go to device manager I see: “Pololu USB Devices” and under that is “Pololu USB AVR Programmer”. This was also on the working laptop. However, there is also a tab labeled “Other devices” which shows under it “Pololu USB AVR Programmer Programming Port” and “Pololu USB AVR Programmer TTL Serial Port” – Both of these have a little yellow caution sign (triangle with exclamation point).

Ive spend a good 5+ hours troubleshooting this, and my best guess is a driver problem.

When I looked up “Driver File Details” for the “Pololu USB AVR Programmer” on the working laptop, 3 files are shown: winusb.sys, WdfCoInstaller01007.dll, and WinUSBCoInstaller.dll
I did the same thing on the laptops that are not working and I see only the “winUSB.sys”

Through the installation of the software, there were error messages that told me to install the *.inf files by hand, (right click, install) which I did.

Thank you all, Please help me out! It is much appreciated, and please ask me if there is anymore information that I could supply! I also took many pictures of the process, if that would help anyone. :smiley:


Hello, Nader.

I’m sorry you are having trouble with the Pololu USB AVR Programmer.

Let’s focus on one computer where the programmer isn’t working and try to get it working on that computer.

Could tell me the name of the setup file you downloaded and where you found it? Instead of paraphrasing error messages, could you please post the complete, exact error message you got during the installation process? That error message should contain a file name and an error code.

From what you described, it sounds like the installation of the programmer’s two virtual COM ports did not succeed. Could you double click on “Pololu USB AVR Programmer Programming Port” in your Device Manager and tell us the exact text you see in the “Device status” box?

On my Windows 7 computer with working drivers I see winusb.sys, WdfCoInstaller01007.dll, and WinUSBCoInstaller.dll listed as driver files for the “Pololu USB AVR Programmer” entry.


Hey, Thank you for your reply!
Error messages I got are "There was an error installing the driver file C:\Program Files\ Pololu\USB\ AVR Programmer\pgm03a.inf
YOu may have to manually install this file by right clicking it and selecting “Install”.
Error Code 2.

I got the same message for the path C:\Program FIles\ Pololu\USB\ AVR Programmer\ pololu_usb_to_serial.inf

On my windows 7 machine WITH the working drivers, I too have winusb.sys, WdfCoInstaller01007.dll, and WinUSBCoInstaller.dll listed as driver files for the “Pololu USB AVR Programmer” entry; however, on the windows 7 machine WITHOUT working drivers, I only see winusb.sys

Let me know if theres more information I should include. Thank you again!

– Nader

Error code 2 is “The system cannot find the file specified.”. I would not expect the system to be able to find a file with the bizarre names you quoted. I would expect the names to be more like: “C:\Program Files\Pololu\USB AVR Programmer\pololu_usb_to_serial.inf”. Did you type the file names exactly as they appear in the error message or did you insert some extra slashes and spaces?

Could you double click on “Pololu USB AVR Programmer Programming Port” in your Device Manager and tell us the exact text you see in the “Device status” box?

I have something for you to try which often resolves issues like this: First of all, try unplugging the programmer from USB and then plugging it back in. Then, in the Device Manager, if you still have Pololu entries inside “Other Devices”, right click on the “Pololu USB AVR Programmer Programming Port” entry, select “Update Driver Software…”, select “Browse my computer for driver software…”, and then enter the name of the directory that contains pololu_usb_to_serial.inf (should be “C:\Program Files\Pololu\USB AVR Programmer” if you have a 32-bit machine and installed in the default location). If you continue through and finish the sequence of dialogs, Windows should attempt to install drivers for the virtual COM port. Let me know what exact errors messages you see at this stage, if any.


Hey David,

My apologies, I did insert extra slashes and spaces.
It should be:
C:\Program Files\Pololu\USB\AVR Programmer\pgm03a.inf
C:\Program Files\Pololu\USB\AVR Programmer\pololu_usb_to_serial.inf

I double clicked on “Pololu USB AVR Programmer Programming Port” in Device Manager and in “Device Status” the exact message was

I also attempted to update the driver software but I got this message:

Hello, Nader.

Here is a working link to your image: … hoot1.jpg/

For future reference, this image shows an error message from Windows for installing the drivers for the Programming Port, and the core part of it was “The system cannot find the file specified.”

Feel free to upload your screenshots here as attachments to your forum post instead of posting them on 3rd party websites.

Too bad Windows isn’t telling us which file it can’t find. The file pololu_usb_to_serial.inf only refers to 3 other files, and they should all be provided by Microsoft as part of your OS. Could you try searching your C:\Windows directory for the files “usbser.sys”, “usb.inf”, and “mdmcpq.inf”? Please let me know how many files you find with those names and tell me the full paths of all of the ones you found. (Windows has a search feature you can use.)