The first and most basic program you can upload to your Arduino is the classic Blink sketch. This takes something on the board and makes it, well, blink! On and off. It's a great way to make sure everything is working and you're uploading your sketch to the right board and right configuration.
When all else fails, you can always come back to Blink!
Pre-Flight Check: Get Arduino IDE & Hardware Set Up
This lesson assumes you have Arduino IDE set up. This is a generalized checklist, some elements may not apply to your hardware. If you haven't yet, check the previous steps in the guide to make sure you:
- Install the very latest Arduino IDE for Desktop (not all boards are supported by the Web IDE so we don't recommend it).
- Install any board support packages (BSP) required for your hardware. Some boards are built in defaults on the IDE, but lots are not! You may need to install plug-in support which is called the BSP.
- Get a Data/Sync USB cable for connecting your hardware. A significant amount of problems folks have stem from not having a USB cable with data pins. Yes, these cursed cables roam the land, making your life hard. If you find a USB cable that doesn't work for data/sync, throw it away immediately! There is no need to keep it around, cables are very inexpensive these days.
- Install any drivers required - If you have a board with a FTDI or CP210x chip, you may need to get separate drivers. If your board has native USB, it probably doesn't need anything. After installing, reboot to make sure the driver sinks in.
- Connect the board to your computer. If your board has a power LED, make sure its lit. Is there a power switch? Make sure its turned On!
Start up Arduino IDE and Select Board/Port
OK now you are prepared! Open the Arduino IDE on your computer. Now you have to tell the IDE what board you are using, and how you want to connect to it.
In the IDE find the Tools menu. You will use this to select the board. If you switch boards, you must switch the selection! So always double-check before you upload code in a new session.
Then in the new window, copy and paste this text:
int led = LED_BUILTIN;
void setup() {
// Some boards work best if we also make a serial connection
Serial.begin(115200);
// set LED to be an output pin
pinMode(led, OUTPUT);
}
void loop() {
// Say hi!
Serial.println("Hello!");
digitalWrite(led, HIGH); // turn the LED on (HIGH is the voltage level)
delay(500); // wait for a half second
digitalWrite(led, LOW); // turn the LED off by making the voltage LOW
delay(500); // wait for a half second
}
One note you'll see is that we reference the LED with the constant LED_BUILTIN rather than a number. That's because, historically, the built in LED was on pin 13 for Arduinos. But in the decades since, boards don't always have a pin 13, or maybe it could not be used for an LED. So the LED could have moved to another pin. It's best to use LED_BUILTIN so you don't get the pin number confused!
Verify (Compile) Sketch
OK now you can click the Verify button to convert the sketch into binary data to be uploaded to the board.
Note that Verifying a sketch is the same as Compiling a sketch - so we will use the words interchangeably
During verification/compilation, the computer will do a bunch of work to collect all the libraries and code and the results will appear in the bottom window of the IDE.
If something went wrong with compilation, you will get red warning/error text in the bottom window letting you know what the error was. It will also highlight the line with an error.
For example, here I had the wrong board selected - and the selected board does not have a built in LED!
Here's another common error, in my haste I forgot to add a ; at the end of a line. The compiler warns me that it's looking for one - note that the error is actually a few lines up!
On success you will see something like this white text output and the message Done compiling. in the message area.
Upload Sketch
Once the code is verified/compiling cleanly you can upload it to your board. Click the Upload button.
The IDE will try to compile the sketch again for good measure, then it will try to connect to the board and upload a the file.
This is actually one of the hardest parts for beginners because it's where a lot of things can go wrong.
However, lets start with what it looks like on success! Here's what your board upload process looks like when it goes right:
Often times you will get a warning like this, which is kind of vague:
No device found on COM66 (or whatever port is selected)An error occurred while uploading the sketch
This could be a few things.
First up, check again that you have the correct board selected! Many electronics boards have very similar names or look, and often times folks grab a board different from what they thought.
If you're positive the right board is selected, we recommend the next step is to put the board into manual bootloading mode.
Native USB and manual bootloading
Historically, microcontroller boards contained two chips: the main micro chip (say, ATmega328 or ESP8266 or ESP32) and a separate chip for USB interface that would be used for bootloading (a CH430, FT232, CP210x, etc). With these older designs, the microcontroller is put into a bootloading state for uploading code by the separate chip. It allows for easier uploading but is more expensive as two chips are needed, and also the microcontroller can't act like a keyboard or disk drive.
Modern chips often have 'native' USB - that means that there is no separate chip for USB interface. It's all in one! Great for cost savings, simplicity of design, reduced size and more control. However, it means the chip must be self-aware enough to be able to put itself into bootload/upload mode on its own. That's fine 99% of the time but is very likely you will at some point get the board into an odd state that makes it too confused to bootload.
Before continuing we really, really suggest turning on Verbose Upload messages, it will help in this process because you will be able to see what the IDE is trying to do. It's a checkbox in the Preferences menu.
Enter Manual Bootload Mode
OK now you know it's probably time to try manual bootloading. No problem! Here is how you do that for this board:
To enter the bootloader on this Feather, hold down the Boot button (highlighted in red above), then press the Reset button (highlighted in blue above). Continue holding the Boot button until the RPI-RP2 drive appears! Then release the Boot button. The board is now in the bootloader!
Once you are in manual bootload mode, go to the Tools menu, and make sure you have selected the bootloader serial port. It is almost certain that the serial port has changed now that the bootloader is enabled
Now you can try uploading again!
This time, you should have success!
After uploading this way, be sure to click the reset button - it sort of makes sure that the board got a good reset and will come back to life nicely.
It's also a good idea to try to re-upload the sketch again now that you've performed a manual bootload to get the chip into a good state. It should perform an auto-reset the second time, so you don't have to manually bootload again.
Finally, a Blink!
OK it was a journey but now we're here and you can enjoy your blinking LED. Next up, try to change the delay between blinks and re-upload. It's a good way to make sure your upload process is smooth and practiced.
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