Assignment 2 Setup


The goal for this task is to get more comfortable with your Photon, and to get it set up and working reliably with your computer for local programming and debugging.


You’ll get credit for following these instructions and being prepared in class. You’ll lose credit for not being ready to be hands-on in class.

Note: Some people weren’t ready last time. I’m going to be lenient for that one, but this time I will deduct points for failing to have everything set up! So: start now, and if you are having problems, post to Slack right away.

Connecting your Photon

If you got your Photon working with your computer in class (that is, if you were able to type particle identify and get an answer), great! Otherwise, get it working.

If you are using Windows, it turns out you need to install a driver. Here are instructions.

Install Particle Dev

Particle Dev is a program for writing code on your computer, so you don’t have to save all of your programs in the cloud. This step is optional; you can also use your favorite text editor. If you’d like to install Particle Dev, you can get a version for your operating system here1.

Local programming

Getting local compiling working is tricky and beyond the scope of this class (you can read all about it here if you want to try); but you can compile remotely and flash2 locally using the particle utility.

First, you need some code on your computer. Using Particle Dev or your favorite text editor, make a new directory called blinky and put a file called blinky.ino into it with the following content:

void setup()
    pinMode(D7, OUTPUT);
void loop()
    digitalWrite(D7, HIGH);
    digitalWrite(D7, LOW);

Now switch to your command prompt, and run particle compile photon <path to your blinky folder> --saveTo blinky.bin3. This command will compile your code remotely on Particle’s servers and print something like

attempting to compile firmware
pushing file: /private/tmp/f/blinky/blinky.ino
grabbing binary from:
Compile succeeded.
Saved firmware to: /private/tmp/f/blinky.bin

Now you’re going to flash that code to your Photon over USB. Plug your Photon into your computer and set it to DFU4 mode:

  1. Hold down BOTH buttons
  2. Release only the RESET button, while holding down the SETUP button.
  3. Wait for the LED to start flashing yellow (it will flash magenta first)
  4. Release the SETUP button

When it’s flashing yellow, it’s ready to accept code over USB. Now you’ll type particle flash --usb blinky.bin. You’ll see a bunch of stuff printed out, which hopefully includes File downloaded successfully. You might also see a bunch of meaningless errors (see Troubleshooting below).

At this point, your Photon should reboot, try to connect to the Internet, and start flashing the D7 LED once per second.

Debugging over USB

It’s useful to be able to see some information about what’s going on with your program. Let’s print out every time the LED turns on or off. First, change your blinky.ino file to the following:

void setup()
    pinMode(D7, OUTPUT);
void loop()
    digitalWrite(D7, HIGH);
    Serial.println("Turned LED on!");
    digitalWrite(D7, LOW);
    Serial.println("Turned LED off!");

Now follow the procedure we did above, starting with the button sequence to get it into DFU mode with the flashing yellow LED (here I’m assuming I’m in the same directory as the blinky folder):

particle compile photon blinky --saveTo blinky.bin
particle flash --usb blinky.bin

Assuming that worked, now let’s look at the output. The easiest way is to:

  1. Open up Particle Dev
  2. Click on the USB icon at the bottom left of the screen
  3. Find the port that your Photon is connected to (on Mac it will look like /dev/cu.usbmodem1234)
  4. Click “Connect”

On Linux (and on Mac if you didn’t install Particle Dev) you can type screen /dev/tty....

You should now see Turned LED on! and Turned LED off! being printed repeatedly.


dfu-util errors

If you get the errors

File downloaded successfully
dfu-util: Error during download get_status

Error writing firmware...dfu-util: Invalid DFU suffix signature
dfu-util: A valid DFU suffix will be required in a future dfu-util

dfu-util: Error during download get_status

don’t necessarily worry. The “File downloaded successfully” part is the good bit, and the other errors are bugs in the code uploader.

Flashing magenta

If you end up with a problem where your Photon doesn’t seem to want to take the code, and every time you flash it reboots and just blinks magenta (purple), try this:

  1. Put the Photon into DFU mode (flashing yellow)
  2. Run particle update
  3. Try again


  1. If you’re running Linux, you can get instructions here

  2. Meaning to put the code you wrote on your Photon. 

  3. Handy tip: on Mac, you can drag the folder from the Finder into your Terminal window and it will put in the path for you! 

  4. “Device Firmware Update”—find an animated gif of the procedure here