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Motor Speed Control Program with ADC and LCD Integration

This embedded systems program, written in C for a PIC18F4321 microcontroller, orchestrates motor speed modulation. Leveraging analog-to-digital conversion, it reads sensor data, transforming it into voltage readings. The LCD interface displays these results, providing real-time feedback. The code dynamically adjusts the motor's speed based on specific voltage thresholds, ensuring optimal performance. Global variables manage pulse parameters, allowing precise control over the motor's behavior. The program encapsulates a continuous loop, perpetually sampling sensor data, updating motor speed, and reflecting outcomes on the LCD. This amalgamation of ADC and LCD functionalities empowers the microcontroller to regulate the motor's operation with responsiveness and efficiency.

Program Architecture and Integration

This section delves into the intricacies of the presented C program designed for the PIC18F4321 microcontroller. By seamlessly combining analog-to-digital conversion and LCD functionalities, the program achieves sophisticated motor speed control. The continuous loop structure efficiently manages pulse parameters, ensuring precise adjustments in response to real-time sensor readings. Emphasizing both responsiveness and efficiency, this section elucidates the intricacies of integrating ADC and LCD functionalities to create a robust system. Additionally, for those seeking assistance with C assignment related to embedded systems and microcontroller programming, this program serves as a practical reference, offering insights into effective implementation and integration strategies.

Block 1: Header Files and Configuration Bits

#include #include #include #include #include #include #pragma config WDT = OFF #pragma config LVP = OFF #pragma config BOR = OFF #pragma config OSC = INTIO2


  • This block includes necessary header files and configuration bits for the microcontroller.
  • Header files provide definitions and functions for the LCD, analog-to-digital conversion, and general I/O operations.
  • Configuration bits are used to set specific options for the microcontroller, like watchdog timer, low voltage programming, brown-out reset, and oscillator selection.

Block 2: Define and Global Variables

#define SPEED LATBbits.LATB3 int result, result_i, result_d; char ch_result[16]; float result_f; int period; // variable to control the period int on_time; // variable to control the pulse on time


  • This block defines a macro SPEED for accessing the third bit of the LATB register.
  • Global variables are declared to store various results, including integer, decimal, and string representations of the sensor reading.
  • Variables period and on_time control the period and pulse on time of the motor, respectively.

Block 3: Port Configuration

TRISBbits.TRISB3 = 0; // Enable A pin TRISBbits.TRISB2 = 0; // Phase A - Directional control pin


  • This block configures the microcontroller's port B pins as outputs to control the motor.
  • Bit 3 is set as the enable pin (SPEED).
  • Bit 2 is set as the directional control pin.

Block 4: LCD Initialization

TRISD = 0; // Set port D as output LCDInit(); LCDClear(); CursorHome(); CursorMode(); DispControl();


  • This block initializes the LCD and configures it for display control.

Block 5: ADC Configuration and Reading

OpenADC(ADC_FOSC_32 & ADC_RIGHT_JUST & ADC_12_TAD, ADC_CH0 & ADC_INT_OFF & ADC_REF_VDD_VSS, 14); Delay10TCYx(5); ConvertADC(); while (BusyADC()); result = ReadADC(); CloseADC();


  • This block configures the Analog-to-Digital Converter (ADC) for channel 0, triggers a conversion, and reads the result.
  • The ADC result is then stored in the variable result.

Block 6: Voltage Conversion and Display

result_f = (result * 5) / 1023.0; result_i = (result * 5 / 1023); result_d = ((result_f - result_i) * 100); sprintf(ch_result, "%d, %d.%d V ", result, result_i, result_d);


  • Converts the ADC result to a voltage reading.
  • Splits the result into integer and decimal parts and formats them into a string (ch_result).

Block 7: Motor Control

on_time = (result * 50 / 1023); period = 100; if (result_i >= 5) { // Motor at maximum speed // ... } // Similar blocks for other speed conditions


  • Calculates on_time based on the ADC result and sets a fixed period.
  • Adjusts motor speed based on the conditions specified.

Block 8: LCD Update and Delay

LCDClear(); DStrToLCD(ch_result); Delay1KTCYx(50);


  • Clears the LCD, writes the sensor result, and introduces a delay before the next iteration.

Block 9: Infinite Loop and Return

while (1) { // Main loop // ... } return 0;


  • The program enters an infinite loop, continuously reading the sensor, updating the motor speed, and displaying results on the LCD.


In conclusion, this meticulously crafted C program for the PIC18F4321 microcontroller exemplifies a harmonious integration of analog-to-digital conversion and LCD functionalities, showcasing a sophisticated approach to motor speed control. Its continuous loop structure, coupled with precise pulse parameter management, ensures the optimal performance of the motor. Beyond its technical prowess, this program stands as a valuable resource for individuals grappling with C assignments in the realm of embedded systems and microcontroller programming. Its intricacies provide not only a practical reference for implementation but also insights into the seamless incorporation of diverse functionalities. By exploring and understanding this code, learners and developers alike can glean valuable knowledge to tackle challenges in C programming and embedded systems development.