Node MCU

Microcontroller Overview

• Microcontroller: PIC16LF1829-I/SS
  • Features:
    • Power Supply: Operates at 3.3V (regulated by the TPS79333 voltage regulator).
    • I/O Ports:
      • RA0 to RA5: Configured for digital I/O and debugging (ICSPDAT/ICSPCLK pins).
      • RC0 to RC7: Connected to RGB LED control and other outputs.
      • RB7 and RB6: Interface with the button and I2C communication lines (SDA, SCL).
    • Special Functions:
      • Supports In-Circuit Serial Programming (ICSP).
      • I2C communication interface.
      • General-purpose Input/Output pins for LED driving and button interface.
  • Applications:
    • LED color control.
    • Sensor data acquisition (accelerometer).
    • User input processing.

Power Management

• Battery and USB Power:
  • The system can be powered either by a battery or USB.
  • The battery voltage (+VBAT) is managed by a BAT54CLT1G Schottky diode to avoid reverse current flow.
  • USB 5V input passes through LED1, providing a visual power-on indicator.
• Voltage Regulator: TPS79333
  • Converts input voltage (+VIN) to a stable 3.3V for the microcontroller and peripherals.
  • Uses decoupling capacitors (C1 and C2) for noise reduction.

RGB LED Control

• LED2: MHS110FRGBCT RGB LED
  • Driving Circuit:
    • Controlled via three transistors (Q1, Q2, Q3 - 2N7002).
    • Resistors (R1, R2, R3 - 300Ω) limit the current for each color channel (Red, Green, Blue).
    • Color brightness and mixing controlled by PWM signals from RC4, RC5, and RC6.

Accelerometer Interface

• Accelerometer: KXTJ3-1057
  • Communication: I2C interface (SDA, SCL) connected to the microcontroller.
  • Power Supply: Operates at 3.3V.
  • Interrupt Pin (INT): Provides event notifications to the microcontroller.
  • Decoupling Capacitors: C4 and C8 ensure stable operation and noise filtering.

User Input

• Button (SW1):
  • A push-button connected to RB7 with a pull-up resistor (R12 - 10kΩ).
  • Provides user interaction, e.g., for triggering events or modes.

Debugging Interface

• ICSP Header (H2):
  • Provides In-Circuit Serial Programming for firmware updates and debugging.
  • Pins include VPP (Programming Voltage), ICSPDAT, ICSPCLK, and GND.

Connector Headers

• I2C and Button Header (H3):

  • Exposes I2C lines and button signal for external devices or debugging.

• LED Header (H4):

  • Provides access to RGB LED control signals and power lines (+VIN, GND).

Additional Parameters

• Resistor Values:
  • Pull-up Resistors: R10, R11, R12 (10kΩ).
  • Current-Limiting Resistors: R1, R2, R3 (300Ω).
• Capacitor Values:
  • Decoupling Capacitors: C1, C2, C3, C4, C8 (1µF, 10µF, and 100nF).
• Diode: BAT54CLT1G for reverse current protection.
• Indicators:
  • LED1 (Green): Indicates USB power status.