🧠⚡ STM32 “Pot-to-Stepper” Project (HAL)

A tiny embedded creature that reads a potentiometer, decides its mood (inactive/work/error), and spins a stepper motor accordingly.
Built mostly with STM32 HAL, designed to be simple, readable, and easy to extend.

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🧩 What this code does (in human words)

• ✅ Reads a potentiometer via ADC1
• ✅ Converts ADC value (0…4095) → percentage (0…100) with safe math
• ✅ Uses the percentage to choose a system mode
  • ≤ 20% → inactive_mode
  • 20–80% → work_mode
  • ≥ 80% → error_mode
• ✅ In work_mode, selects motor direction based on thresholds
  • 30–40% → clockwise
  • 60–70% → anticlockwise
  • else → motor inactive
• ✅ Drives a stepper motor (half-step / 8-step sequence) on GPIOF pins PF0..PF3
• ✅ Uses TIM3 interrupt as a simple “cycle tick” (increments a counter)
• ✅ Sends a tiny UART “hello” (currently transmits byte 3) over USART3

If this were a pet:

• Potentiometer = its “food meter”
• LEDs = its “mood ring”
• Stepper motor = its “legs” 🐾

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⏱️ Timing model (how the “scheduler” works)

TIM3 as a periodic tick:

• HAL_TIM_PeriodElapsedCallback() checks if it was TIM3
• then calls increment_cycle_count(&global_system)
• which increments: global_system.u8_system_cycle_time++

In main.c, the loop likely checks this counter and runs the algorithm once per “cycle”, then resets it to 0.

So it’s basically a tiny cooperative scheduler:

• ISR: tick++
• main loop: if tick reached → do work → tick = 0

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🔁 The main workflow (high level)

Mermaid Flowchart

flowchart TD
  A[Boot] --> B[initialization()\nHAL + clocks + GPIO + ADC + TIM3 + UART3]
  B --> C[system_init(&global_system)]
  C --> D{Main Loop}
  D -->|cycle tick reached| E[read_sensor_value()\nADC read]
  E --> F[process_sensor_readings()\nADC -> %]
  F --> G[system_mode_selection()\n% -> system_mode]
  G --> H[system_mode_operation()\nLED + work logic]
  H --> I[system_execution()\nstepper move or idle]
  I --> J[send_info_on_bus()\nUART3 byte]
  J --> K[change_in_mode()\nreset LED on mode change]
  K --> L[reset cycle counter]
  L --> D
  D -->|no tick| D

Loading

ASCII fallback (if Mermaid isn’t supported)

[ init HAL ] -> [ system_init() ] -> main loop:
      |
      +--> if cycle tick:
              ADC read -> % calc -> mode select -> mode op
                          -> motor exec -> UART tx -> mode change check
                          -> reset tick

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🌀 Stepper motor sequence (half-step, 8 states)

stepper_motor_sequence(step) uses these patterns:

Step	Coil pattern
0	1000
1	1100
2	0100
3	0110
4	0010
5	0011
6	0001
7	1001

And then energize_pins() writes the states to GPIO.

Direction functions:

• clockwise_movement() steps 7 → 0
• anitclockwise_movement() steps 0 → 7

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🎛️ Mode logic (the “personality” of the system)

1) System mode selection (from pot percentage)

In system_mode_selection():

• ≥ 80% → error_mode
• ≤ 20% → inactive_mode
• otherwise → work_mode

2) Work mode motor direction selection

In work_mode_operation():

• 30–40% → clockwise (clock_wise_rotation)
• 60–70% → anticlockwise (anticlock_wise_rotatin)
• else → motor inactive

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🧪 UART “bus” output

send_info_on_bus() currently transmits a single byte:

• tx_uart = 3

There’s also a commented snippet to transmit the potentiometer percentage. If you want telemetry, you can expand this to send a small structured frame like:

[0xAA][percent][mode][direction][CRC]

(Keeping it simple but “debugger-friendly”.)

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🛠️ Build & Flash (typical STM32CubeIDE flow)

1. Open the project in STM32CubeIDE
2. Build
3. Flash via ST-Link
4. Watch LEDs + motor behavior as you rotate the potentiometer

If you’re using a Nucleo board, make sure the GPIOF pins are actually available (some boards don’t break out all PF pins).

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🧯 Troubleshooting

• Motor doesn’t move

  • Check stepper driver wiring + power (separate motor supply often needed)
  • Confirm PF0..PF3 are configured as outputs in CubeMX
  • Confirm coil order matches your driver inputs (swap IN pins if direction/steps look wrong)

• ADC always reads 0 or max

  • Check ADC channel pin mapping in CubeMX (MX_ADC1_Init())
  • Verify pot wiring: 3.3V – wiper – GND

• Timer tick not happening

  • Ensure HAL_TIM_Base_Start_IT(&htim3); is called (it is in initialization())
  • Confirm TIM3 interrupt enabled in NVIC

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🧾 License

If you don’t have a license yet: choose one (MIT is friendly). Otherwise it’s the classic: “works on my desk” 😄

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👤 Author

VIN — January 2026 (Embedded + HAL + a stepper motor that refuses to be boring.)