Robotic-Arm

Firmware for a 6-axis, mostly-3D-printed desktop robot arm. Runs on an Arduino Mega 2560 + RAMPS 1.4 with six TB6560 stepper drivers, plus a hobby servo for the gripper.

The codebase is a fork of Marlin by way of the BCN3D Moveo firmware, reworked for this arm's mechanics.

Status: working firmware, but parts of this README are still TODO — flagged inline. PRs welcome.

Hardware this firmware is written for

• MCU: Arduino Mega 2560
• Driver shield: RAMPS 1.4
• Steppers: 6× TB6560 external drivers, driving 1× Nema 14, 2× Nema 17, 1× Nema 17 + 5:1 planetary, 2× Nema 23 (3 Nm)
• Gripper: 13 kg·cm hobby servo
• PSU: 24 V / 320 W, with a 24→12 V buck for fans / logic-side rails

The full mechanical BOM, STLs and assembly guide live with the project page on Printables — see the project description.

Repository layout

All firmware sources currently sit at the repo root. Notable files:

File	What it is
Marlin.ino / Marlin_BCN3D_Moveo.ino	Sketch entry point. TODO: confirm which one is canonical and remove the other — Arduino IDE will not happily compile a folder containing two .ino files with different names.
Configuration.h	The file you'll edit most: board selection, axis steps/mm, max feedrates, endstop polarity, baud rate.
Configuration_adv.h	Advanced tunables (acceleration shaping, watchdog, thermal protection — most of which is irrelevant for an arm with no hotend).
pins.h	Pin map for every Marlin-supported board. The active map is selected by the MOTHERBOARD define in Configuration.h.
planner.cpp / stepper.cpp / motion_control.cpp	Motion core, inherited from Marlin. The 6-axis plumbing for this arm lives here — see source.
ultralcd*.{h,cpp}, dogm_*.h, cardreader.{h,cpp}	Optional LCD + SD-card UI, inherited from Marlin. Disable in Configuration.h if you aren't using an LCD.
language_*.h	Locale strings for the LCD, inherited from upstream Marlin. Only language_en.h is needed for this build.
qr_solve.{h,cpp}, vector_3.{h,cpp}	Linear-algebra helpers — likely used for inverse-kinematics / coordinate transforms. See source.

TODO: the STL files, BOM, and CAD source are not currently in this repo. Decide whether to add a hardware/ folder or to point at the Printables page.

Building and flashing

With the Arduino IDE

1. Install the Arduino IDE (1.8.19 or newer, or 2.x).
2. Clone this repo. Rename the cloned folder so its name matches the .ino file you're keeping — the IDE requires sketch folder name == sketch file name. So either:
   • keep Marlin.ino and rename the folder to Marlin/, or
   • keep Marlin_BCN3D_Moveo.ino and rename the folder to Marlin_BCN3D_Moveo/.
3. Open the .ino in the IDE. All .h/.cpp files in the folder will load as tabs.
4. Board: Arduino Mega or Mega 2560. Processor: ATmega2560.
5. Pick the right serial port, hit Upload.

No external libraries are needed — Servo, LiquidCrystalRus, SdFat, and the U8glib display drivers are all vendored in the repo.

With PlatformIO (recommended for reproducible builds)

TODO: there is no platformio.ini in the repo today. Adding one targeting board = megaatmega2560 and framework = arduino would let people build from the command line without touching the IDE. Contributions welcome.

Configuration — what you'll need to edit

Before the first flash, open Configuration.h and confirm:

• MOTHERBOARD — must be set to the RAMPS 1.4 variant. TODO: confirm exact value (e.g. BOARD_RAMPS_14_EFB).
• BAUDRATE — pick a value your host tool supports (Marlin default is 250000; many BCN3D Moveo forks use 115200). TODO: confirm.
• DEFAULT_AXIS_STEPS_PER_UNIT — must be calibrated for this arm's gear ratios per joint. TODO: publish the calibrated values.
• INVERT_*_DIR — flip per joint after the first power-on direction check.
• Endstop enables and *_HOME_DIR — depend on whether you've wired physical endstops to RAMPS.
• Thermistor / heater settings — disable; this arm has no hotend or heated bed.

Configuration_adv.h rarely needs touching for a first run.

Pin assignments

The active pin map is selected by MOTHERBOARD in Configuration.h and resolved in pins.h. RAMPS 1.4 only provides 5 stepper sockets natively (X, Y, Z, E0, E1); the 6th axis is wired to spare pins.

TODO: lift the per-axis STEP / DIR / EN / endstop pins for this build into a table here, plus whichever RAMPS header the 6th driver is hooked to and the gripper-servo pin. Until then, see pins.h (the section guarded by your MOTHERBOARD define) and the wiring section of the assembly guide.

Driving the arm

TODO: confirm the control method.

• If it's host-side G-code over USB, document baud and the joint-to-axis-letter mapping (e.g. J1→X, J2→Y, …, J6→E1), and give an example: G1 X10 F500.
• If it's the LCD + SD card path, document which display the firmware is built for (the manifest contains both a Hitachi HD44780 implementation and a DOGM/u8glib one) and how to load a .gcode file.
• If there's a host-side GUI, link it.

Troubleshooting

• "Compile error: redefinition of loop" or the IDE refusing to open the sketch — caused by having two .ino files in the folder. Delete one (see Building above).
• All axes home in the wrong direction — flip the relevant INVERT_*_DIR in Configuration.h. Don't move them by hand under power.
• One joint never moves — check the TB6560 enable logic (active-low on RAMPS) and the per-driver microstepping DIP switches before suspecting firmware.
• MCU resets under load — almost always a power problem (24 V rail sagging, or USB sharing logic ground with the motor return). The watchdog (watchdog.cpp) will reboot cleanly; the symptom is real.

Credits

• Marlin — the firmware core (planner, stepper, serial, LCD/SD).
• BCN3D Moveo — the original arm-shaped Marlin fork this build is derived from.

License

The firmware in this repo is derived from Marlin and is therefore distributed under GPL-2.0-or-later. The upstream LICENSE file should be committed alongside this README — TODO.

Mechanical / CAD assets (STLs, BOM, drawings) on the project page are released under TODO: confirm CC-BY / CC-BY-NC / CC-BY-SA.