MT6701 ENCODER

MESC BRAIN BOARD

A PCB and software development project for a balancing robot.

The goal is to use a hobby Electronic Speed Controller (one open source example, and this circuit for a brain board, a teensy 4.0, and an ESP-32, in combination with MESC firmware.

GENERAL APPROACH

A separation of concerns is divided across these architectures:

• Teensy: Runs the high-level brain → gait generator, balance estimator, RC inputs
• MESC: The firmware on the ESC for control → torque or velocity loops per joint
• ESP32: Easy to log and analyze later → pumps UDP to the computer
• Desktop computer → perfectly adequate way of viewing high speed data with UDP

TEENSY 4.0

• 600+ MHz ARM Cortex-M7 — plenty of headroom for filtering, control loops, gait logic, telemetry
• Tons of I/O for IMU, encoders, RC input, WiFi (via ESP add-on), etc.
• Precise timing with elapsedMicros or interrupts for deterministic control
• Great for real-time control, sensor fusion, and behavior modeling

MESC MOTOR CONTROLLER

• Deploys on simple DIY or commercially available ESC boards
• Executes low-level Field-Oriented Control (FOC) motor control
• Built-in support for encoders, FOC, and torque estimation
• Accurate low-level motor control using current sensing
• Reads angular position from the MT6701 encoder via SPI or PWM
• UART/CAN interface (RX + TX) Real-time communication with the Teensy
• PWM / FOC commutation w/ efficient, smooth motor operation

OTHER BRAIN BOARD FEATURES

• RC receiver connector (for PWM/PPM/SBUS input)
• ESP32 UART serial programmer
• Power input connector
• Voltage divider (to monitor battery voltage)
• Push-button E-stop connector
• Power button (for system on/off)
• IMU connector (e.g., MPU-6050)
• Buzzer (for system alerts or E-stop signal)
• MESC I/O
• Reserved 2 GPIO pins on Teensy for emergency shutoff to MESC
• CAN connector (for MESC motor control)

CAN BUS

• Full-duplex communication between Teensy and motor controllers
• Carries:
  • Commands: set_torque, set_velocity, enable_motor, zero_encoder, etc.
  • Telemetry: encoder position, estimated torque, velocity, fault codes
• Real-time performance with minimal latency
• Can support multiple motor controllers on the same bus

MANY THANKS

This project would never happen without:

• MESC firmware.
• Netzpfuscher's incredible TTerm and CAN work.
• MP2 an open source motor controller from badgineer.

NOTES

Ever wanted to change all the names of kicad files at once?

use this:

python3 replace_kicad_names.py VESC_brain_board MESC_brain_board

[LINK]

STILL NEEDS WORK

• Not great design w/ DC-DC conversion from high voltage VBat
• Replace out the IMU for a ICM-42688-P
• Order / revise pushbuttons for programming the ESP32
• Ensure 3.3V CAN transciever

VERSIONS

• See github tag pcb-v1 for V1.0
• Retreive with this command: "git checkout pcb-v1"