StepUp! - A no-code tool for instant stepper motor testing

What is it?

StepUp! is a low-cost, battery powered handheld device for quick testing and development work with any sized stepper motor - all you need is:

A stepper motor
A motor cable

Why did you make it?

Working a lot with stepper motors, I often find myself wanting to test a single motor at a time to understand if its performing as it should - often with questions like:

Is there an issue with my driving circuit or the motor itself?
Is the cabling damaged or do the coils contain open or short circuits?
Does it have a hold current or is it jammed?

I found that, to really answer these questions required power supplies, microcontrollers, stepper motor driving circuitry, a PC to compile and upload firmware and a programmatic approach to moving a motor. What I needed was a simpler way to control motors that felt intuitive - something battery powered and ideally joystick controlled.

I came to the realisation that this problem was two-fold:

I don’t have an easy & repeatable way of driving stepper motors
I don’t always have all of my lab equipment set up to make the kind of measurements I care about.

I set out to tackle problem number 1 - creating an easy way to repeatably test a stepper motor

What makes it special?

There are plenty of boards and solutions out there that can drive a stepper motor. However, what I have yet to see is a solution that is completely self-contained, requiring no external power supply and driving a stepper motor using input controls from an operator.

My aim is for this to be an item in your toolbox, one that can be called upon whenever you need to test a motor - without all the setup cost.

It is inherently low power - giving just enough juice to get a motor going but with enough power to test out some motor features.

How much does it cost to build?

Short answer

Around €50 (or $60) per unit

Longer answer...

A core goal from the outset was to make this as cheap as I possibly could. Totting up my most recent order for 5 PCB's with 3 assembled PCBA's and including the additional through-hole components I hand solder to the PCBA's (to reduce cost) works out to around $50 per PCB as per my last order in March 2025.

Tech specs

Firmware: Pico-SDK v2.2.0 running FreeRTOS v11.2.0
CPU: Dual-core Arm Cortex-M0+ processor, flexible clock running up to 133 MHz
RAM: 264kB on-chip SRAM
Flash: 2MB on-board QSPI flash
Battery: 18650 Li-Ion, single cell (protected or non)
Charge current: 300mA
Motor control: ~10.2V at 500mA (default) -> 5.1 Watts
Battery life: ~5.5 hours in testing using a 3400mAh 18650 Li-Ion battery

Pre-requisites

Assembling a StepUp! device

All documentation and pre-requisites for creating your own StepUp! PCB and enclosure can be found in the Hardware README file.

IDEs

This project was developed using Microsoft Visual Studio Code and all instructions which follow mention use of its code extensions for working with the StepUp! project. Workspace files are included herein - see rp2040.code-workspace.

Quick-start - cloning the repo and uploading code

Clone (recursively) the repo: git clone --recursive https://github.com/SJFOM/StepUp-Pico.git.
Enter the repo: StepUp-Pico.
Optionally, edit CMakeLists.txt and /App-StepUp/CMakeLists.txt to configure the project.
Optionally, manually configure the build process: cmake -S . -B build/.
Optionally, manually build the app: cmake --build build.
Connect your device so it’s ready for file transfer.
Copy the StepUp.uf2 file from the build/App-StepUp folder to the drive which represents the attached Pico device hardware.

VS Code extensions

Required

Raspberry Pi's own VSCode extension simplifies the installation process for any OS. It includes other necessary VS Code extensions such as CMake and Cortex-Debug for both CMake file compilation and debugging using OpenOCD via a SWD capable debugger probe respectively.

Optional

While the Raspberry Pi Pico extension is the only one required to compile code for this project, an ancilliary list of recommended extensions can be found in the included extensions.json file and will be prompted for install by the VS Code IDE.

Project Structure

/StepUp-Pico
|
|___/App-StepUp             // StepUp! Application source code (C++)
|   |___CMakeLists.txt      // Application-level CMake config file
|
|___/Config
|   |___FreeRTOSConfig.h    // FreeRTOS project config file
|
|___/FreeRTOS-Kernel        // FreeRTOS kernel files, included as a submodule
|
|___/images                 // Image files used in the README.md guides
|
|___/Hardware               // Thin layers for global control - used as parent class
|   |___3D print files      // STL files to be 3D printed for StepUp housing
|   |___PCBA files          // Zip file containing Gerbers, Drill files & BoM 
|
|___/Interfaces             // Thin layers for global control - used as parent class
|
|___/Libraries              // Non-HW specific code, commonly used function calls
|
|___CMakeLists.txt          // Top-level project CMake config file
|___pico_sdk_import.cmake   // Raspberry Pi Pico SDK CMake import script
|
|___rp2040.code-workspace   // Visual Studio Code workspace
|
|___README.md
|___LICENSE.md

Using the device

Steps 1 -> 3 below should be followed in the order provided to give best chances of uploading code first time!

If helpful, all PCB schematics for this project can be found in the Releases section of my KiCad repository.

1. Inserting a battery

Only 18650 Li-Ion cells are supported by this device. The 18650 cell can either include battery protection circuitry or not - there is a battery protection circuit on-board the StepUp! device which is configured specifically for the device and will prevent device power-on if reverse polarity is detected. See the Hardware README file for reference on assembly process.

NOTE: When first inserting the battery, you must also plug in a USB C cable to power up the device. This is a known quirk of the battery protection circuit which prohibits using the battery until external power is first applied.

2. Uploading code to the device

Once a battery has been inserted, plug the device into your PC using a USB C data cable.

Due to a small hardware quirk, you need to ensure that the POWER button (on the side) is held down for the duration of the programming process. Follow these steps to upload code:

Press and hold the POWER button on the side of the PCB (or Enclosure box) and the PROGRAM button on the bottom of the PCB (or Enclosure box)
Press once the RESET button to reboot the device into program mode.
You can now release the PROGRAM button but keep the POWER button held down

The device should evaluate as a USB drive mounted to your PC. From here, you can copy the StepUp.uf2 file to the mounted device either:

By grabbing the latest copy of Release firmware available in the GitHub repo
OR - locating it in the build/App-StepUp directory once you have compiled this repository

Only now, once the device has been successfully programmed can you release the POWER button.

3. Powering ON

Once firmware has been loaded successfully - press and hold the POWER button on the side of the device until the LED flashes GREEN several times and an audible tone of increasing frequencies plays (like a step-up sequence).

4. Controlling the Motor

Connection

Connect the stepper motor using the connector labelled with A1, A2, B1, B2 to match the coils of the given motor, lifting the 4 black tabs of the connector to allow insertion of the wires and then closing each of the 4 black tabs down with an audible "click" once the wires are in place. The wires should ideally have at least 5mm of exposed wire to ensure a good connection.

Joystick control

The Joystick is used to control the motor direction and speed. If you increase or decrease the speed of the motor and then return the joystick to the center, the next time you move the motor the device will attempt to ramp up to the previous speed the motor was running at. To reset this behaviour to the original starting speed, press the joystick button.

Motor current

By default, the StepUp! device drives the supplied stepper motor with ~500mA of current. While this can be increased by modifying the firmware (see DEFAULT_IRUN_VALUE in tmc_control.hpp) it is not recommended given the limited power available from the provided 18650 battery.

5. Status Codes

USB Connection

The StepUp! device emits a stream of serial messages over USB which can be read while the device is operating - especially if any error message needs to be further diagnosed. The following is an example output stream when the device boots - see drop-down item below.

StepUp! USB boot-up serial logs

[INFO] App: StepUp 1.0.0 (9134303:2)
[INFO] Setting up peripherals...
[INFO] Watchdog setup...
[INFO] Watchdog setup... OK
[INFO] Buzzer setup...
[INFO] Buzzer setup... OK
[INFO] LED setup...
[INFO] LED setup... OK
[INFO] TMC2300 setup...
[INFO] TMC - UART pins enable
[INFO] TMC2300 silicon version: 0x40
[INFO] Configure TMC2300 default values...
[INFO] TMC2300 GSTAT register diagnostics:
[INFO]  - Reset?: 1
[INFO]  - Driver shutdown due to error?: 0
[INFO]  - Low supply voltage?: 0
[DATA] Run current: 515 mA
[INFO] Configure TMC2300 default values - OK!
[INFO] TMC2300 setup... OK
[INFO] Boost converter setup...
[INFO] Boost converter setup... OK
[INFO] Voltage monitoring setup...
[DATA] Battery voltage: 4.15V
[INFO] Battery voltage monitoring setup... OK
[DATA] Motor voltage: 10.25V
[INFO] Boost/Motor voltage monitoring setup... OK
[INFO] Voltage monitoring setup...OK
[INFO] Joystick setup...
[DATA] X - Raw value: 2048 - voltage: 1.65V
[DATA] Y - Raw value: 2048 - voltage: 1.65V
[INFO] Joystick setup... OK
[INFO] Setting up peripherals... OK!
[INFO] FreeRTOS timer started successfully!
[INFO] TMC is ready for use

`STANDBY` - When not controlling a stepper motor

Status	Color: Pattern	Buzzer Pattern	Meaning
Power ON	Green: Fade, low to high	Sequence, low to high	Device is booting - boot complete once tone completes
Power ON	Green: Fade, low to high -> Slow blinking Red for 5 seconds -> Solid Red LED	Sweep, low to high -> Continuous beep tone for 5 seconds	Device is booting - fails during boot
Ready	Green: Solid	None	Device is ready, LED colour indicates battery HIGH
Ready	Orange: Solid	None	Device is ready, LED colour indicates battery MEDIUM
Ready	Red: Solid	None	Device is ready, LED colour indicates battery LOW
Power OFF	Red: Fast Blinking	Long continuous	Battery critically LOW - Device auto-powers OFF
Power OFF	Red: Fast Blinking	Sequence, high to low	User has triggered a power OFF sequence

`ACTIVE` - When controlling a stepper motor

Status	Color: Pattern	Buzzer Pattern	Meaning
Joystick button press	Blue: Fast blinking	Two quick beeps	Reset motor speed to initial starting value
Motor moving	Red: Rapid Blinking	Three long beeps	Error detected - issue could be any of the following: Short circuit in motor coils, Open circuit, TMC Overheating, battery voltage out of bounds, motor voltage out of bounds
Motor moving	White: Solid for ~1 second	None	Momentary motor stall event, unable to provide full power due to excessive motor speed. Note: A stall event may occur and the motor will happily continue spinning, it is purely indicative of the loading on the motor driver circuitry

6. Powering OFF

Press and hold the POWER button on the side of the device for 5 seconds until the LED flashes RED several times and an audible tone of decreasing frequencies plays (like a step-down sequence).

NOTE: The device has an auto power-down feature and will automatically power OFF after 10 minutes of inactivity.

Charging

When the USB cable is inserted, a small orange LED near the USB port will illuminate indicating the battery is being charged. The battery is fully charged once the LED extinguishes.

NOTE: The StepUp! PCB charges at a modest 300mA. While not the fastest charging speed out there, it is safe and keeps the temperature of the onboard charging IC down.

Debugging

NOTE: The device must first be powered ON for debugging to be enabled.

While any debug probe offering SWD debugging will work, this project makes use of the very handy Raspberry Pi Debug Probe and the launch.json file in this repository is configured as such for use with this probe.

A debugging session can be started either through the Raspberry Pi Pico extension or by using the Run and Debug extension in the VS Code sidebar. In either case, use the Pico Debug (Cortex-Debug) prompt when asked how you want to initalise the session.

Debugging on MacOS

To get openocd to play ball, you must install the following libraries as described in the openocd/README.macOS file:

brew install libtool automake libusb libusb-compat hidapi libftdi

Debugging in Linux

Enable `arm-none-eabi-gdb`

To debug in Linux, you need to ensure you have arm-none-eabi-gdb installed. If you can build firmware for the Pico, odds are this is already installed on your PC but not symlinked correctly. To link this, run the following with elevated priveleges (sudo)

ln -s /usr/bin/gdb-multiarch /usr/bin/arm-none-eabi-gdb

You should now see that running arm-none-eabi-gdb works as expected.

Note on use Linux for debugging

To help Linux to recognise the debug probe, you may need to update your udev rules by following the very useful steps outlined here. This will configure your udev rules to recognise the Pico plugged in as a CMSIS-DAP interface.

The relevant steps in the linked guide are as follows:

Create a file 10-my-usb.rules in /etc/udev/rules.d containing

SUBSYSTEM=="usb", ATTRS{idVendor}=="2e8a", ATTRS{idProduct}=="000c", MODE="666", GROUP="plugdev"

Now, restart the udev service using

sudo udevadm control --reload
sudo udevadm trigger

Credits

This work makes heavy usage of Tony Smith's (a.k.a smittytone) wonderful RP2040-FreeRTOS Template which forms the basic structure for most of this project. Kudos to his work on creating a simple platform to get started with FreeRTOS on the Pi Pico hardware.

Name		Name	Last commit message	Last commit date
.github/workflows		.github/workflows
.vscode		.vscode
App-StepUp		App-StepUp
Config		Config
FreeRTOS-Kernel @ 0adc196		FreeRTOS-Kernel @ 0adc196
Hardware		Hardware
Interfaces		Interfaces
Libraries		Libraries
development_utilities/CRC		development_utilities/CRC
images		images
teleplot layouts		teleplot layouts
.bazelignore		.bazelignore
.bazelrc		.bazelrc
.bazelversion		.bazelversion
.clang-format		.clang-format
.gitignore		.gitignore
.gitmodules		.gitmodules
CMakeLists.txt		CMakeLists.txt
FreeRTOS_Kernel_import.cmake		FreeRTOS_Kernel_import.cmake
LICENSE		LICENSE
LICENSE.md		LICENSE.md
MODULE.bazel		MODULE.bazel
MODULE.bazel.lock		MODULE.bazel.lock
README.md		README.md
pico_sdk_import.cmake		pico_sdk_import.cmake
rp2040.code-workspace		rp2040.code-workspace

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