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CircuitPython runs Python programs directly on your GLYPH board. This guide covers flashing the firmware with Thonny or esptool, connecting with Thonny, and saving a program that runs whenever the board starts.
Flashing CircuitPython replaces the firmware currently on the board. Save any existing sketches or files you need before continuing. Download the firmware for your exact GLYPH model; a different board’s image can have the wrong flash layout or pin definitions.

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Download Thonny and your board firmware

  1. Install Thonny for your operating system.
Thonny installation screen
  1. Open the CircuitPython download page for your board: GLYPH C3, GLYPH C6, GLYPH H2, or GLYPH S3 (search for PCBCupid GLYPH S3).
CircuitPython website showing board downloads
  1. Download the latest stable .bin firmware for that board. Keep track of where the file was saved.
Downloading the CircuitPython .bin file for GLYPH C3
  1. Connect the GLYPH to your computer with a USB data cable.

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Flash CircuitPython with Thonny

  1. Hold BOOT, press and release RESET, then release BOOT. If the board has no RESET button, hold BOOT while plugging in the USB cable. The board should appear as a serial port.
  2. In Thonny, open Tools → Options → Interpreter and select the ESP32 interpreter to access Install or update firmware. Open the firmware installer.
  3. Select the serial port for your GLYPH, choose the .bin file you downloaded, and set the start address to 0x0. CircuitPython ESP32 images must be flashed at 0x0, even if a MicroPython preset suggests another address.
  4. Click Install and wait for the success message. Disconnect and reconnect the board, or press RESET with BOOT released.
If Thonny does not offer the correct chip or start address, use the OPEN INSTALLER button on the board’s CircuitPython download page to flash the same firmware, then return to Thonny for editing. Close Thonny’s serial connection before opening the browser installer.

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Install esptool in a terminal

If you prefer flashing from a terminal, install Python 3.10 or newer and run:
The second command confirms that esptool is available. On macOS or Linux, use python3 instead of python if that is how Python is installed. If your system blocks a global pip install, follow Espressif’s virtual environment instructions.

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Flash CircuitPython with esptool

  1. Download the .bin file for your exact GLYPH model from the link above. Close Thonny and any serial monitor so esptool can use the port.
  2. Put the board in bootloader mode: hold BOOT, press and release RESET, then release BOOT. If there is no RESET button, hold BOOT while plugging in USB.
  3. Open a terminal in the folder containing the downloaded .bin file. Replace COM5 with your board’s serial port (for example, /dev/ttyACM0 on Linux or /dev/cu.usbmodem... on macOS) and firmware.bin with the actual downloaded filename:
  1. Wait for esptool to finish writing and verifying the image. Press RESET with BOOT released, or unplug and reconnect the board. Then connect with Thonny to save code.py.
esptool terminal output while flashing CircuitPython Use python3 -m esptool if you installed esptool with python3. The 0x0 flash address is required for the downloaded CircuitPython ESP32 .bin image; see Espressif’s write-flash command reference.

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Connect Thonny and run code

  1. In Tools → Options → Interpreter, choose CircuitPython (generic) and select the GLYPH serial port. The Shell should show the CircuitPython >>> prompt. Press Ctrl+C if a running program occupies the Shell.
Selecting the CircuitPython interpreter and serial port in Thonny
  1. Paste the following example into a new Thonny editor tab. Change the GPIO number to your board’s onboard LED: C3: 1, C6: 14, H2: 0. For other models, check that board’s pinout.
  1. Choose File → Save as, select CircuitPython device, and save the file as code.py. CircuitPython runs code.py automatically at startup and after you save it. Use the Thonny Shell for print() output and errors.
CircuitPython test code running in Thonny
The C3, C6, and H2 use a serial connection and may not show a CIRCUITPY USB drive. Save files to CircuitPython device in Thonny. On a board that does show a CIRCUITPY drive, saving code.py there works too.

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Add libraries for the examples

The basic GPIO examples only use built-in CircuitPython modules. Sensor and display examples name any extra adafruit_*.py files they need. Download the CircuitPython library bundle that matches your firmware’s major version, then copy the named files and their dependencies into the board’s lib/ directory using Thonny’s device file browser. Keep the filenames and folder structure from the bundle.

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If the board is not detected

  • Try a different USB data cable or port and close any other serial monitor.
  • Re-enter bootloader mode with BOOT and RESET before flashing. After flashing, reset with BOOT released.
  • Check that the firmware download matches the exact GLYPH board and that the flash start address is 0x0.
  • Reopen the CircuitPython interpreter and select the new serial port if its port name changed after flashing.