Hello everyone,

I am facing a deeply perplexing issue with my stepper motor setup on a BIGTREETECH Octopus Pro board, and I desperately need technical insights. I have exhausted standard online guides and firmware troubleshooting.

1. Hardware Specifications

• Motherboard: BIGTREETECH Octopus Pro V1.1 (MCU: STM32H723ZE variant)
• Stepper Driver: TMC2209
• Stepper Motor: 17HE15-1504S (NEMA 17, 1.5A)
• Firmware: Marlin
• Power Supply: 24V DC MeanWell PSU

2. Core Symptoms & Behavior

• Under 24V Power Input: The motor exhibits a very strong holding torque (the shaft locks up rigidly and cannot be rotated by hand). However, when I send a movement command (e.g., G1 X20 F60) via Pronterface, the motor does absolutely nothing. There is no rotation, no vibration, and no audible frequency hum whatsoever. It remains completely locked.
• Under USB 5V Power Only (24V disconnected): If I cut the 24V power supply and only power the logic via USB-C, sending the exact same movement command results in a distinct, directional pulse/force felt on the motor shaft. While it lacks the high-voltage torque to fully rotate, the STEP/DIR signal sequence is clearly reaching the motor coils. The moment 24V is reapplied, it returns to a completely silent, stationary lock.

3. Troubleshooting Already Conducted

• Endstop Interferences (M119): Initially, all min endstops were stuck on TRIGGERED due to logic configuration. I inverted them in Configuration.h (X_MIN_ENDSTOP_HIT_STATE LOW), and running M119 now correctly returns open for all axes.
• Command Sequence: To bypass any firmware safety limits during testing, I used: PlaintextG92 X0 M211 S0 G91 G1 X20 F60
• Driver Modes & Physical Jumpers: 1. UART Mode: Set #define X_DRIVER_TYPE TMC2209 in Marlin. Placed a single jumper on the designated CS-CS pin according to the BTT manual. M122 continuously outputs Error: All LOW. 2. Standalone Mode: Changed firmware to TMC2209_STANDALONE. Removed UART jumpers and placed jumpers on MS1/MS2 for hardware 16-microstepping interpolation, and shorted the SLP-RST pins.
  • Result: The behavior is completely identical in both configurations (locked solid on 24V with zero movement/vibration, but directional pulses felt under USB 5V).
• VREF Tuning: Adjusted the potentiometer from 0V up to 1.0V (and briefly up to 1.7V to check protection cutoffs). The holding torque intensity scales properly with VREF adjustments, but no movement is triggered.
• Wiring Verification: Verified coil pairs using a multimeter. Phase A is mapped to pins 1-2, and Phase B is mapped to pins 3-4. The fact that directional pulses are felt during the USB-only test confirms the wiring order delivers the phase sequence.
• Thermal Sensors (M105): Since I am testing the motor standalone without hotend/bed thermistors connected, M105 reports T:-15.00. However, Marlin accepts commands and executes stepping routines normally without throwing a hard heater kill halt.

4. The Main Question

Why does the stepper driver successfully pass the STEP/DIR pulses to the motor coils when running on low USB 5V voltage, but completely ignore/filter out the high-frequency step pulses and remain in a dead holding lock the moment 24V VM (Motor Power) is supplied?

Could this point to a physical hardware defect on the Octopus board (such as a failed level shifter or isolating optocoupler), a cooked driver internal gate logic, or a critical timing mismatch in Marlin regarding the high-speed STM32H723 clock cycles?

Any testing methods, firmware overrides, or hardware diagnoses would be highly appreciated. Thank you.