API Documentation v0.0.1
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Flashing Firmware from CI Artifacts

Table of Contents

This guide explains how to download pre-built firmware from the OpenHornet CI pipeline and flash it to your microcontrollers using free, open-source command-line tools — no Arduino IDE required.

Overview

Every time code is merged into the main or develop branch (and on every pull request), the GitHub Actions Continuous Integration (CI) pipeline automatically compiles all OpenHornet sketches. The resulting firmware files are bundled into a downloadable artifact called firmware. This artifact is available for 7 days after each workflow run.

There are two kinds of compiled firmware files depending on which microcontroller the sketch targets:

File extension Board type Flashing tool
.hex + .eep Arduino MEGA 2560, SparkFun Pro Micro, Arduino Pro Mini avrdude
.bin WEMOS S2 Mini (ESP32-S2) esptool.py

Step 1 — Download the Firmware Artifact

  1. Open the OpenHornet-Software repository in your browser.
  2. Click the Actions tab at the top.
  3. In the left sidebar, click Continuous Integration.
  4. Click the most recent successful run (green checkmark) on the branch you want (typically main).
  5. Scroll to the bottom of the run page to find the Artifacts section.
  6. Click firmware to download the zip file.
  7. Extract the zip — you will find a flat folder of .hex, .eep, and .bin files, one set per sketch.

Each file is named after the sketch it belongs to (e.g., 1A2-MASTER_ARM_PANEL.hex). Use the table in Sketch-to-Board Reference to find the right file for your panel.

Step 2 — Install the Flashing Tools

avrdude (for AVR boards — MEGA 2560, Pro Micro, Pro Mini)

  • Windows: Download and install the Arduino IDE. avrdude is bundled inside it, or install it standalone via the WinAVR package. After installation, avrdude is typically found at C:\Program Files (x86)\Arduino\hardware\tools\avr\bin\avrdude.exe.
  • macOS: brew install avrdude
  • Linux: sudo apt install avrdude (Debian/Ubuntu) or your distro's equivalent.

Verify: avrdude -v should print version information.

esptool.py (for WEMOS S2 Mini — ESP32-S2)

Requires Python 3.7+.

pip install esptool

Verify: esptool.py version should print version information.

Step 3 — Find Your COM Port

You need to know which serial port your microcontroller is on before flashing.

Windows: Open Device Manager (press Win + X → Device Manager) and expand Ports (COM & LPT). Your board will appear as something like COM3 or COM7. Note down the port name.

macOS:

ls /dev/cu.*

Look for something like /dev/cu.usbmodem14201 or /dev/cu.usbserial-XXXX.

Linux:

ls /dev/ttyACM* /dev/ttyUSB*

Look for /dev/ttyACM0, /dev/ttyACM1, /dev/ttyUSB0, etc. If you have multiple USB devices, plug the board in and out while running the command to see which entry appears and disappears.

Step 4 — Flash the Firmware

Replace <PORT> with your actual port (e.g., COM3 on Windows or /dev/ttyACM0 on Linux/macOS) and <SKETCH> with the sketch name from the artifact folder.

Arduino MEGA 2560

Used by: bus master panels (1A1, 2A1A1, 4A1A1, 5A1A1), backlight controller (2A13), COMM panel (4A7A1), and standby instruments (2A7A1).

avrdude -p m2560 -c wiring -P <PORT> -b 115200 -D \
-U flash:w:<SKETCH>.hex:i \
-U eeprom:w:<SKETCH>.eep:i

Example (Windows):

avrdude -p m2560 -c wiring -P COM4 -b 115200 -D -U flash:w:1A1-UIP_ABSIS_BUS_MASTER.hex:i -U eeprom:w:1A1-UIP_ABSIS_BUS_MASTER.eep:i

Example (Linux/macOS):

avrdude -p m2560 -c wiring -P /dev/ttyACM0 -b 115200 -D -U flash:w:1A1-UIP_ABSIS_BUS_MASTER.hex:i -U eeprom:w:1A1-UIP_ABSIS_BUS_MASTER.eep:i

SparkFun Pro Micro (ATmega32U4, 16 MHz)

Used by: the majority of OpenHornet panels. See Sketch-to-Board Reference for the full list.

The Pro Micro uses the Caterina USB bootloader. Because the board presents itself as a USB device, flashing requires a brief reset window:

  1. Trigger the bootloader: Quickly double-tap the reset button on the Pro Micro. The board will enter the bootloader for about 8 seconds, during which a new COM port briefly appears. You must run the avrdude command while the bootloader port is active.
  2. Run the flash command immediately after double-tapping reset, targeting the bootloader port (which may be a different COM number than the normal operating port).
avrdude -p atmega32u4 -c avr109 -P <BOOTLOADER_PORT> -b 57600 -D \
-U flash:w:<SKETCH>.hex:i \
-U eeprom:w:<SKETCH>.eep:i

Example (Windows):

avrdude -p atmega32u4 -c avr109 -P COM5 -b 57600 -D -U flash:w:1A2-MASTER_ARM_PANEL.hex:i -U eeprom:w:1A2-MASTER_ARM_PANEL.eep:i

Example (Linux/macOS):

avrdude -p atmega32u4 -c avr109 -P /dev/ttyACM1 -b 57600 -D -U flash:w:1A2-MASTER_ARM_PANEL.hex:i -U eeprom:w:1A2-MASTER_ARM_PANEL.eep:i

‍Tip: On Linux you may need to add your user to the dialout group to access the serial port without sudo: sudo usermod -aG dialout $USER (log out and back in after).

Arduino Pro Mini (ATmega328P, 8 MHz)

Used by: 4A9A1A1-THROTTLE_INNER_GRIP.

The Pro Mini does not have a USB port of its own — you need a USB-to-serial adapter (e.g., FTDI FT232 or CP2102) connected to its TX/RX/GND/DTR pins.

avrdude -p atmega328p -c arduino -P <PORT> -b 57600 \
-U flash:w:<SKETCH>.hex:i \
-U eeprom:w:<SKETCH>.eep:i

Example (Windows):

avrdude -p atmega328p -c arduino -P COM6 -b 57600 -U flash:w:4A9A1A1-THROTTLE_INNER_GRIP.hex:i -U eeprom:w:4A9A1A1-THROTTLE_INNER_GRIP.eep:i

Example (Linux/macOS):

avrdude -p atmega328p -c arduino -P /dev/ttyUSB0 -b 57600 -U flash:w:4A9A1A1-THROTTLE_INNER_GRIP.hex:i -U eeprom:w:4A9A1A1-THROTTLE_INNER_GRIP.eep:i

WEMOS S2 Mini (ESP32-S2)

Used by: 4A9A1-THROTTLE_CONTROLLER.

The artifact contains a single merged binary (.bin) that includes the bootloader, partition table, and application in one file.

Put the board into download mode first:

  1. Hold the BOOT (IO0) button.
  2. While holding BOOT, press and release RESET.
  3. Release BOOT. The board is now in download mode.
esptool.py --chip esp32s2 --port <PORT> --baud 921600 \
write_flash 0x0 <SKETCH>.bin

Example (Windows):

esptool.py --chip esp32s2 --port COM7 --baud 921600 write_flash 0x0 4A9A1-THROTTLE_CONTROLLER.bin

Example (Linux/macOS):

esptool.py --chip esp32s2 --port /dev/ttyUSB0 --baud 921600 write_flash 0x0 4A9A1-THROTTLE_CONTROLLER.bin

After flashing completes, press RESET once to start running the new firmware.

Sketch-to-Board Reference

Use this table to find which firmware file belongs on which panel and which flash command to use.

Sketch (firmware filename prefix) Panel Name Board Flash Command
1A1-UIP_ABSIS_BUS_MASTER UIP Bus Master Arduino MEGA 2560 MEGA 2560
1A2-MASTER_ARM_PANEL Master Arm Panel SparkFun Pro Micro Pro Micro
1A3-L_DDI_AND_EWI L DDI / EWI SparkFun Pro Micro Pro Micro
1A6-SPIN_RCVY_PANEL Spin Recovery Panel SparkFun Pro Micro Pro Micro
1A7-HUD_PANEL HUD Panel SparkFun Pro Micro Pro Micro
1A9-R_DDI_AND_EWI R DDI / EWI SparkFun Pro Micro Pro Micro
2A13-BACKLIGHT_CONTROLLER Backlight Controller Arduino MEGA 2560 MEGA 2560
2A1A1-LIP_ABSIS_BUS_MASTER LIP Bus Master Arduino MEGA 2560 MEGA 2560
2A2A1-LEFT_LIP_MODULE Left LIP Module (IFEI) SparkFun Pro Micro Pro Micro
2A3A1-AMPCD AMPCD SparkFun Pro Micro Pro Micro
2A4A1-RWR_CONTROL_PANEL RWR Control Panel SparkFun Pro Micro Pro Micro
2A7A1-STANDBY_INSTR_MODULE Standby Instruments Arduino MEGA 2560 MEGA 2560
3A2A1-SEAT_CONTROLS Seat Controls SparkFun Pro Micro Pro Micro
3A3A1-STICK_CONTROLLER Stick Controller SparkFun Pro Micro Pro Micro
4A1A1-LC_ABSIS_BUS_MASTER LC Bus Master Arduino MEGA 2560 MEGA 2560
4A2A1-LDG_GEAR_PANEL Landing Gear Panel SparkFun Pro Micro Pro Micro
4A3A1-SELECT_JETT_PANEL Select Jettison Panel SparkFun Pro Micro Pro Micro
4A3A3-FIRE_TEST_PANEL Fire Test Panel SparkFun Pro Micro Pro Micro
4A4A2-EXT_LIGHTS_PANEL Exterior Lights Panel SparkFun Pro Micro Pro Micro
4A5A1-FUEL_PANEL Fuel Panel SparkFun Pro Micro Pro Micro
4A5A2-APU_PANEL APU Panel SparkFun Pro Micro Pro Micro
4A6A1-FCS_PANEL FCS Panel SparkFun Pro Micro Pro Micro
4A7A1-COMM_PANEL COMM Panel Arduino MEGA 2560 MEGA 2560
4A7A2-OBOGS_PANEL OBOGS Panel SparkFun Pro Micro Pro Micro
4A9A1-THROTTLE_CONTROLLER Throttle Controller WEMOS S2 Mini S2 Mini
4A9A1A1-THROTTLE_INNER_GRIP Throttle Inner Grip Arduino Pro Mini Pro Mini
5A10-DEFOG_PANEL Defog Panel SparkFun Pro Micro Pro Micro
5A1A1-RC_ABSIS_BUS_MASTER RC Bus Master Arduino MEGA 2560 MEGA 2560
5A5A1-ECS_PANEL ECS Panel SparkFun Pro Micro Pro Micro
5A6A1-INTR_LT_PANEL Interior Lights Panel SparkFun Pro Micro Pro Micro
5A7A1-SNSR_PANEL Sensor Panel SparkFun Pro Micro Pro Micro
5A8A1-SIM_CNTL_PANEL Sim Control Panel SparkFun Pro Micro Pro Micro
5A9A1-KY58_PANEL KY-58 Panel SparkFun Pro Micro Pro Micro

Troubleshooting

avrdude: stk500v2_ReceiveMessage(): timeout The MEGA 2560 is not responding. Make sure the correct COM port is selected and the board is powered. Try pressing the reset button once and immediately running the command.

avrdude: butterfly_recv(): programmer is not responding The Pro Micro bootloader window has closed. Double-tap reset again and re-run the avrdude command faster.

avrdude: ser_open(): can't open device Wrong COM port, or your user lacks permission (Linux). Check Device Manager / ls /dev/tty* again. On Linux, run sudo usermod -aG dialout $USER and re-login.

esptool: A fatal error occurred: Failed to connect to ESP32-S2 The board is not in download mode. Repeat the BOOT + RESET button sequence and try again. On some setups you may need to lower the baud rate: replace 921600 with 460800 or 115200.

Artifact has expired / not found CI artifacts are kept for 7 days. If the artifact is gone, trigger a new CI run by pushing a commit or asking a maintainer. Alternatively, build the firmware locally — see the Software Manual.

Wrong firmware / board bricked Flash the correct .hex/.bin file for that panel using the table above. If a board appears completely unresponsive, it may need a bootloader re-burn — see the OpenHornet Discord for help.