DC Motor Controller — STM32F103

Closed-loop DC motor controller for the STM32F103RCTx (Cortex-M3, 72 MHz), with a companion web-based GUI for real-time tuning and monitoring.

The firmware implements a cascade PID control scheme — an optional outer position loop feeds a velocity setpoint into an inner velocity loop — and communicates with the GUI over UART. Built with STM32 HAL and Python/FastAPI.

DC_Motor_Controller/
├── FW/   ← STM32 firmware (C, STM32CubeIDE)
├── SW/   ← Web GUI (Python backend + HTML/JS frontend)
└── docs/ ← Hardware photos, specs

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Architecture

  Encoder (PA0 / PA1)
        │
        ▼
  TIM2  [Quadrature counter — TI12 ×4]
        │  delta counts / 10 ms
        ▼
  Motor2_Speed_Update()
  └── 8-sample moving average → RPM
        │
        ├─────────────────────────────────────────────┐
        │  [Velocity Mode]                            │  [Position Mode]
        │                                             │
        │  setpoint_rpm ──► PID Velocity ◄── rpm     │  setpoint_counts ──► PID Position
        │                        │                   │                           │
        │                        │ duty (−100…+100)  │       vel_sp (RPM)  ◄─────┘
        │                        │                   │           │
        │                        └───────────────────┼───► PID Velocity
        │                                            │           │
        └────────────────────────────────────────────┘           │
                                                           duty (−100…+100)
                                                                  │
                                                                  ▼
                                                    Motor2_SetOutput(signed_duty)
                                                                  │
                                              ┌───────────────────┴──────────────────┐
                                              │                                      │
                                       TIM3_CH3 (forward)                    TIM3_CH4 (reverse)
                                              │                                      │
                                              └──────────────┬───────────────────────┘
                                                             │
                                                         H-Bridge
                                                             │
                                                         DC Motor

Control tick: SysTick ISR (1 ms) counts to 10 → sets g_control_tick flag → main loop runs one full control cycle.

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Key Specifications

Parameter	Value
MCU	STM32F103RCTx — Cortex-M3 @ 72 MHz
Control loop period	10 ms (100 Hz)
Encoder	Quadrature TI12 mode — 2023 PPR → 8092 CPR
Speed filter	8-sample circular moving average
PWM	Dual-channel — TIM3_CH3 (forward) / TIM3_CH4 (reverse)
PID output range	−100 % … +100 % duty cycle
Velocity PID	Kp = 1.8, Ki = 0.05, Kd = 0.01, N = 0.2
Position PID	Kp = 2.0, Ki = 0.005, Kd = 0.08, N = 0.2

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Modules

driver_rym_v1_pid — Generic PID Controller

Discrete PID with integrator anti-windup (clamp to output limits) and a first-order derivative low-pass filter controlled by coefficient N. Gains and sample period are set at initialisation; internal state can be reset independently of gains via PID_Reset().

PID_Init(&pid_vel, Kp, Ki, Kd, N, dt, out_min, out_max);
float duty = PID_Update(&pid_vel, setpoint_rpm, measured_rpm);

driver_rym_v1_speed — Speed Measurement

Reads the TIM2 hardware quadrature encoder counter at each 10 ms tick, computes RPM from the signed 16-bit delta (wrap-safe), and applies an 8-sample circular moving average with O(1) running sum. Exposes both Motor2_Speed_GetRPM() and Motor2_Speed_GetRadS().

driver_rym_v1_motor — Motor Driver

Controls an H-bridge via two complementary PWM channels. Supports FORWARD, REVERSE, BRAKE, and STOP modes. High-level entry point:

Motor2_SetOutput(int32_t signed_duty);  /* −100 = full reverse, +100 = full forward */

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Pinout

Signal	Pin	Peripheral
Encoder A	PA0	TIM2_CH1
Encoder B	PA1	TIM2_CH2
PWM Forward	PB8	TIM3_CH3
PWM Reverse	PB9	TIM3_CH4
Driver Enable 1	PB5	GPIO output
Driver Enable 2	PB4	GPIO output

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Build

1. Open STM32CubeIDE
2. File → Import → Existing Projects into Workspace → select repo root → Finish
3. Select Debug or Release build configuration → Ctrl+B
4. Flash via ST-Link: Run → Debug, or use STM32CubeProgrammer with Release/DRIVER_RYM_V1.hex