Hello everyone,

I’m currently working on a project that involves controlling a small robot with 3 stepper motors using TMC2208 drivers in standalone mode. However, I’m encountering some issues that I suspect are related to my schematic design. I’ve reviewed the connections multiple times, but I can’t seem to pinpoint the problem. I’m hoping someone here with experience with the TMC2208 can offer some guidance. Schematic and code are attached.

Schematic Details
• Microcontroller: Raspberry Pi Pico
• Stepper Drivers: TMC2208 (3 drivers for 3 axes)
• Power Supply: 12V for motors

Observed Issues
• The stepper motors are not moving at all. Tested with all 3 drivers. No current flowing (steppers can be turned easily by hand).
• Other parts of the PCB (buttons, solenoid) work as expected

What I’ve Tried
• Double-checked the wiring and connections against the TMC2208 datasheet (as good as I can)
• Verified the microcontroller code: The same code on a different RPi Pico (same GPIO usage) attached to a TMC2208 breakout board drives the motors as intended

If anyone can review the schematic and point out any potential issues, it would be extremely helpful. I’m also open to any other suggestions or troubleshooting steps I should undertake.

Thank you in advance for your help!

from machine import Pin, Timer
import utime
dir_pin = Pin(7, Pin.OUT)
step = Pin(8, Pin.OUT)
enable = Pin(9, Pin.OUT)

enable.value(0)
dir_pin.value(1)

def stepOne():
  step.high()
  utime.sleep(0.001)
  step.low()

while True:
  for i in range(3000): ## At 1/8 steps (MS1 0, MS2 0)
    stepOne()
    utime.sleep(0.0001)
  dir_pin.toggle()

PCB Schematic, Page 1 of 2:

Page 2:

 

Looking at the group of details, I see no motor connections. Unless they are called something else. Have you verified that the enable command id being supplied? Lack of enable will certainly stop the show.
OK, it seems that they are in that small segment leading to CN3.
AND, once again, this style of drawing makes understanding a system function require a lot more effort, and certainly it makes it easy to miss details. It would not be accepted in any group that I lead.

 

Motors are attached to CN1-3.
Yes, ENN is connected to the Raspberry Pi Pico and controlled using its GPIOs.

 

Two things stand out looking at your schematic, with respect to the TMC2208's.
First, your current sense resistors on pins BRA and BRB are far too big at 11 Ohms. They would probably be fine for a motor coil current of about 30mA max.
The second and even more problematic is that you don't appear to have any charge pump capacitors for pins CP0 and CP1 (22nF recommended), which will almost certainly prevent the output bridge working!

 

Just out of interest, how did you get on? It's always nice to hear the outcome of a post!

 

My apologies, took me some time to get it sorted.
I've adjusted the schematics, and plan on ordering and testing again. Hopefully, I'm able to report back with good news in a few days. Thanks for the help!