Closed-Loop DC Motor Speed Controller Using TI TMS320F2812

Why This Project?

The TMS320F2812 is an older member of TI's C2000 family, but it was specifically designed around real-time control applications rather than general-purpose embedded processing.

Instead of using the F2812 to blink an LED or read a potentiometer, this project uses several of its peripherals together in a realistic motor-control application.

The basic idea is straightforward:

Measure motor speed → calculate speed error → execute PI control → update PWM duty cycle → measure current → repeat.

The motor is driven by a MOSFET connected to one of the F2812's PWM outputs. An incremental encoder provides feedback about the motor's rotational speed. A current-sense amplifier converts the motor current into a voltage that can be sampled by the F2812's 12-bit ADC.

A periodic control interrupt executes the speed-control algorithm. The measured speed is compared with the requested speed, and a PI controller adjusts the PWM duty cycle.

The F2812 is particularly suitable for this type of experiment because the device combines a C28x CPU with dedicated motor-control peripherals, ADC resources, Event Managers, QEP interfaces, timers, and communication interfaces.

The project also exposes the control variables through SCI/UART. This makes it possible to watch the requested speed, measured speed, PWM duty cycle, and motor current from a PC while the motor is running.

That makes the project useful for people interested in:

• Motor control
• Digital control loops
• C2000 DSPs
• PWM generation
• Encoder feedback
• ADC sampling
• PI controllers
• Power electronics
• Embedded control
• Legacy TI C2000 development
• Reusing older DSP hardware in laboratory equipment

Operating Principle

The control system follows this sequence:

+----------------------+
              |  Speed Reference     |
              |  0 - 3000 RPM        |
              +----------+-----------+
                         |
                         v
                  +-------------+
                  | Speed Error |
                  +------+------+
                         |
                         v
                  +-------------+
                  | PI Control  |
                  +------+------+
                         |
                         v
                  +-------------+
                  | PWM Output  |
                  +------+------+
                         |
                         v
              +----------------------+
              | MOSFET Gate Driver   |
              +----------+-----------+
                         |
                         v
                   +-----------+
                   | DC Motor  |
                   +-----+-----+
                         |
                         v
                  +-------------+
                  |   Encoder   |
                  +------+------+
                         |
                         v
                  +-------------+
                  |    QEP      |
                  +------+------+
                         |
                         +----------------+
                                          |
                                          v
                                    Measured RPM
+----------------------+
              |  Speed Reference     |
              |  0 - 3000 RPM        |
              +----------+-----------+
                         |
                         v
                  +-------------+
                  | Speed Error |
                  +------+------+
                         |
                         v
                  +-------------+
                  | PI Control  |
                  +------+------+
                         |
                         v
                  +-------------+
                  | PWM Output  |
                  +------+------+
                         |
                         v
              +----------------------+
              | MOSFET Gate Driver   |
              +----------+-----------+
                         |
                         v
                   +-----------+
                   | DC Motor  |
                   +-----+-----+
                         |
                         v
                  +-------------+
                  |   Encoder   |
                  +------+------+
                         |
                         v
                  +-------------+
                  |    QEP      |
                  +------+------+
                         |
                         +----------------+
                                          |
                                          v
                                    Measured RPM

A second feedback path measures motor current:

Motor Current
     |
     v
+------------+
| Shunt Res. |
+-----+------+
      |
      v
+-------------+
| Current Amp |
+------+------+
       |
       v
+--------------+
| F2812 ADC    |
| ADC Channel  |
+--------------+
Motor Current
     |
     v
+------------+
| Shunt Res. |
+-----+------+
      |
      v
+-------------+
| Current Amp |
+------+------+
       |
       v
+--------------+
| F2812 ADC    |
| ADC Channel  |
+--------------+

This lets the project demonstrate both control feedback and analog measurement.

Suggested Hardware Test Procedure

Step 1 — Verify the controller

Program a simple GPIO test and verify JTAG communication with the F2812.

Step 2 — Verify PWM

Connect the selected PWM output to an oscilloscope.

Start with:

PWM frequency = 20 kHz
Duty cycle    = 10 %
PWM frequency = 20 kHz
Duty cycle    = 10 %

Verify the waveform before connecting the motor power stage.

Step 3 — Verify ADC

Apply a known voltage to the selected ADC input and compare the measured ADC counts with the calculated voltage.

Step 4 — Verify encoder

Rotate the motor shaft manually and check that the encoder count changes correctly.

Step 5 — Run open-loop

Before enabling closed-loop control, run the motor at a fixed low PWM duty cycle.

For example:

10 %
20 %
30 %
40 %
10 %
20 %
30 %
40 %

Check motor current and encoder feedback at each step.

Step 6 — Enable closed-loop control

Start with a relatively low speed reference:

500 RPM
500 RPM

Then increase gradually:

1000 RPM
1500 RPM
2000 RPM
1000 RPM
1500 RPM
2000 RPM

Tune Kp and Ki while monitoring:

• Speed response
• Overshoot
• Settling time
• Motor current
• PWM duty cycle
• Encoder feedback