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Step 6: Blink an LED

Your first flow: make an LED blink once a second, using three nodes.

Your board should be connected, with the runtime installed: steps 4 and 5.

Find your LED's pin

Many boards have an LED wired to a GPIO pin. To find it, click Pins… next to the Board menu. Pins that the board names, such as LED, are listed first. Supported hardware lists the boards ThingStudio has definitions for. For any other board, check its documentation.

The Pico W and Pico 2 W LEDs are wired through the WiFi chip, not a GPIO pin, so gpio out can't reach them. On those boards, or any board without an LED, wire an LED and a 330 Ω resistor from a free GPIO pin to GND. The LED's longer leg goes towards the GPIO pin.

Don't leave out the resistor. Without it, the LED draws too much current and can damage the board.

Build the flow

  1. Drag a timer onto the canvas. Set interval (ms) to 500.

  2. Drag a function onto the canvas. Replace its code with:

    msg['payload'] = msg['payload'] % 2
return msg

  3. Drag a gpio out onto the canvas. Set pin to your LED's GPIO number.

  4. Wire timer → function → gpio out.

This flow is tutorials/blink.flow.json, in the tutorials folder. Opened from there, it needs only pin set to your LED's GPIO number.

Deploy

Click Compile → Deploy. A successful deploy ends like this in the console:

[deploying "my flow" as 3f2a…]
[deploy OK -- flow is running on the device]

The flow name and ID will differ. Set the console's Show menu to Info or Debug to see each stage, including the board's free memory.

The LED now blinks: on for half a second, off for half a second.

The flow keeps running on the board after you unplug it from your computer and power it another way.

How it works

The timer sends a message every 500 ms. Its payload is a count: 1, 2, 3, and so on.

gpio out turns the pin on for any payload that isn't zero. Wired straight to the timer, the LED would switch on and stay on.

The function node turns the count into 1, 0, 1, 0 with % 2. That gives on, off, on, off.

Next

Two tutorials take the flow further:

  • Two more blinks — the blink again, two more ways: the LED's state on the hardware, read and written back in code, or kept in the node with context.
  • A sensor display — the next job past blinking: read a sensor and show it on a screen.

Tell us how it went

Started from a blank board? Tell us how it went: where the guide or the tool let you down is the most useful part. To keep it private, email mike@minus1.com.

Each symptom below has its own fix:

  • Deploy is grayed out: you aren't connected, so click Connect. Deploy is also grayed out after a deploy until you change the flow, while the flow is stopped at the Python prompt (Stop flow & open prompt), and while the board restarts.
  • Compile fails: usually a mistake in the function node's code, such as a missing quote or wrong indentation. The console shows the Python error in red, with its line, and highlights the node. Fix the code and deploy again.
  • Deploy works, then the console shows [NODE_ERROR]: the code ran on the board and failed, for example on a misspelt name. The message names the error, and the node is highlighted.
  • Deploy fails: the console says why. See Board won't connect.
  • Deploy works but the LED stays dark: check the pin number against Pins…. Some boards' LEDs light when the pin is off; the LED still blinks, the other way round.

For anything else, see Debugging & troubleshooting.