Need help with Pololu USB AVR Programmer #1300


I am trying to combine the Grbl Shield and Arduino Uno together to make a desktop cnc learning project, and have discovered that there are some technical prerequisites that are just assumed and perhaps I should have asked a lot more questions.

I discovered that the Arduino bootloader needs to be flashed ( pardon me if I don’t get the terminology correct at this point ) with the grbl hex file and I would need a USB AVR Programmer to accomplish this, so in looking around I discovered that Pololu had a lot of helpful information especially for me which I am grateful for, thanks very much :slight_smile:

I purchased the Pololu USB AVR Programmer #1300 and downloaded all the documentation and driver files and software and installed it all, and read through the PDF file about the programmer and on page 12 there is a suggestion to “Upgrade your programmer’s firmware to version 1.06 or later. See Section 9 for instructions”, in section 9 of the PDF file on page 52 there is info on how to determine the current firmware revision, I followed those instructions and found the revision to be “1010” I read further and found that I needed to download the terminal program “Br@y terminal” which I did. I downloaded the 1.06 firmware revision from Pololu.

On page 51 there is a paragraph

“To determine the programmer’s revision code in Windows: If you only see one entry for the programmer
in your Device Manager, then you have a special modified firmware version.” -------> I did in fact find this to be true and wasnt sure if I should continue forward or not at that point, I had looked further and discovered the rev as being “1010” so I thought I would follow the intructions for using the “Br@y terminal” program to try and update the firmware.

To make a long story shorter , I am now in this area--------> "Upgrading Firmware
To upgrade your programmer’s firmware, follow these steps:

  1. Once the programmer is in bootloader mode, it will appear to your computer as a new device called
    “Pololu pgm03a Bootloader”.
    Windows 7, Vista and Linux: The driver for the bootloader will automatically be installed.
    Windows XP: When the “Found New Hardware Wizard” is displayed, follow steps 4–6 in Section
    3.a to get the driver working. >>>>>>>> (Done)

  2. Once the bootloader’s drivers are properly installed, the green LED should be blinking in a double heartbeat
    pattern, and there should be an entry for the bootloader in the “Ports (COM & LPT)” list of your
    computer’s Device Manager in Windows. >>>>>>>> (Done)

  3. Use a terminal program (such as Br@y Terminal []) to connect to the
    bootloader’s virtual serial port. In Windows, you can determine the port name of the bootloader (e.g. COM5)
    by looking in the Device Manager. In Linux, you can determine the port name (e.g. /dev/ttyACM0) by
    running dmesg. You can use any baud rate. >>>>>>>> (Done)

  4. Type the following lower-case letters into your terminal program to send them to the bootloader:
    fwbootload. After each letter is sent, the bootloader should echo back the upper-case version of that letter.
    After you have finished typing this sequence, you should see “FWBOOTLOAD” as the output from the
    bootloader in your terminal program, and the programmer’s yellow LED should be on. >>>>>>>> (Done)

Below is where I am stuck the terminal program will not accept the lower case “s” and now I am dead in the water and do not know if I should have even gone this far.

  1. Now send lower-case “s”. The bootloader will spend a few seconds erasing the current firmware and
    settings, and then it will echo back an upper-case S. Do not disconnect the programmer from the computer
    after this point until the upgrade is complete.

  1. Now send the contents of the downloaded firmware upgrade file to the bootloader. The firmware upgrade
    file is a plain-text (ASCII) file, so you can open it in a text editor (such as notepad), copy the whole thing,
    and then paste it into your terminal program. Br@y terminal has a “Send File” button you can use.
  2. While the file is being sent, the bootloader will send back period characters (“….”). This process will
    take about 5 seconds. When the firmware upgrade is complete, the bootloader should send back a pipe
    character (“|”) and turn the red LED on.
  3. You can now unplug your programmer, plug it back into the computer, and use the new firmware.

If you run into problems during a firmware upgrade, please contact us [] for assistance.

My question is at this point can I undo what I have done and try to use the programmer with the “special modified firmware version” to flash the code onto my Arduino Uno?

I am getting so far in over my head here maybe I can find someone that could update my programmer and flash my Arduino with GRBL code so I could get to building and fabricating my desktop 3 axis gantry.


Colin Morris

Hello Colin.

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

This requirement sounds very strange. The Arduino UNO should already have a bootloader on it. Could you post a link to the sentence in the documentation of the grbl shield that makes you think you need to do this? Maybe you don’t need to use our programmer at all.

The instructions on page 12 that you referred to, telling you to upgrade the programmer’s firmware to version 1.06, are in the “Programming AVRs Using AVR Studio 5” section so they only apply if you want to use AVR Studio 5. Currently we are shipping programmers with firmware version 1.01, which works fine with AVR Studio 4 and AVRDUDE.

By the way, I recommend reading the online version of the user’s guide because it looks better and will sometimes be a little more up-to-date than the PDF:

What do you mean when you say Br@y Terminal won’t accept the “s”? What happened and what did you expect to happen? Did you type “s” the same way you typed “fwbootload”? You need to enter it into the white textbox at the bottom and then click the “-> Send” button.

If you have not succeeded in sending the “s” to your programmer yet, then the programmer’s firmware should still be there. I recommending disconnecting the programmer from everything to unpower it, then plugging it back into USB. The programmer’s firmware should then run normally.