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Built-in project · ESP32-DevKitC V4

MicroPython serial echo: input() on an ESP32, on an ESP32-DevKitC V4

MicroPython on an ESP32 with nothing wired: input() reads each line typed into the Serial Monitor and print() answers with it. The whole build, an ESP32-DevKitC V4, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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Teaching? Assign it to your class in one click.

Beginner About 5 minutes to build and run. Runs in your browser. Free, and no account needed.

The parts retail for about $10. On Mokxi they're free.

The circuit runs here once the page has loaded.

What you'll learn

  • Reading typed text with input()
  • Sending text to the Serial Monitor with print
  • Why a loop keeps the program alive
  • Serial as a two way channel
  • Difficulty: Beginner
  • Time: About 5 minutes
  • Board: ESP32-DevKitC V4
  • Parts: 1

How it works

Nothing is wired for this one. The board talks to you through the Serial Monitor. It prints a prompt, then waits.

The input() call blocks until you type a line and press Enter. The script then prints You typed: followed by your text, and goes back to waiting. It is the simplest two way conversation with a board.

Parts list

1 part, plus the jumper wires. They retail for about $10; on Mokxi they're free.

Kits that can build it

These 3 starter kits have every part in the circuit. Each kit's page lists what else it can build.

The code

The MicroPython code exactly as the editor opens it. Change a line there and press Run: the board runs it on the official MicroPython firmware, with nothing to compile.

main.py · ESP32-DevKitC V4
# Serial read and write: type a line into the Serial Monitor and press
# Enter. input() waits for it, and the board answers with what it got.
print("Type something and press Enter")
while True:
    text = input()
    print("You typed:", text)

Troubleshooting

The usual mistakes with this circuit, and the fix for each.

  • Nothing happens when you type This project
    Click in the Serial Monitor's input box, type the text and press Enter. The board only answers after a full line.
  • The board is not found, or upload fails with a connecting message. ESP32-DevKitC V4
    Use a USB cable that carries data, not charge only. Pick the ESP32 Dev Module board. If it still fails, hold BOOT while uploading starts, then release.
  • Some pins never read right, or the board will not boot with a wire attached. ESP32-DevKitC V4
    GPIO34 to 39 are input only and have no pull-ups. GPIO6 to 11 run the flash, so leave them alone. GPIO0, 2 and 12 are boot pins; avoid pulling them the wrong way at reset.

Change it and keep it

Open it in the editor, change the circuit or the code, and keep your version in a free account.

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