PIC10 RS232 Parity Checker using PIC10F202 with Proteus Simulation

How the Project Works (Overview)

This project receives RS232 serial data bit-by-bit on GP0 of the PIC10F202. The firmware manually samples each bit using timing delays instead of a hardware UART.
Eight data bits are captured, followed by a parity bit. The code counts the number of logic-high bits and determines whether the parity condition is valid.
A configuration input on GP2 allows switching between even parity and odd parity checking.
If a parity error is detected, GP1 is asserted to turn on an LED, providing immediate visual feedback.

Block Diagram / Workflow Explanation

1. Wait for Start Bit
   The firmware continuously monitors GP0 until a low start bit is detected.

2. Bit Sampling
   Using calibrated delay loops, the PIC samples each of the 8 data bits at fixed intervals.

3. Bit Counting
   Each logic-high data bit increments a counter to track the number of ‘1’ bits.

4. Parity Evaluation
   The received parity bit and the GP2 parity-mode input are added to the bit count.

5. Error Indication
   If parity validation fails, GP1 drives an LED to indicate an error.

6. Stop Bit & Restart
   After detecting the stop bit, the system resets and waits for the next byte.

Key Features

• Software-based RS232 reception using GPIO

• Supports even and odd parity selection

• Visual parity error indication using an LED

• Minimal hardware with a PIC10 microcontroller

• Fully testable using Proteus VSM simulation

• Demonstrates timing-critical serial data sampling

Components Used

• PIC10F202 Microcontroller

• RS232 terminal (Proteus VTERM)

• LED (error indicator)

• 330Ω resistor

• Power supply and ground connections

Applications

• Learning RS232 communication fundamentals

• Educational embedded systems demonstrations

• Debugging serial data parity behavior

• Testing parity settings from terminal software

• Training projects for low-pin-count microcontrollers

Explanation of the Code (High-Level)

The firmware begins by configuring GPIO directions, with GP0 as input and GP1 as output.
The program waits for a valid RS232 start bit, then samples incoming bits using precise delay loops.
Each received bit is shifted into a byte register while counting the number of logic-high bits.
After reading the parity bit, the code adjusts the bit count based on the selected parity mode (GP2).
If the final count indicates a parity mismatch, the LED output is activated.
The firmware then waits for the stop bit and repeats the process indefinitely.

Source Code

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;PIC10 Parity Checker

        LIST    p=10F202 ; 
	#include "P10F202.INC" ; Include header file

        CBLOCK 0x08   ; Temporary storage
        dc1
        bitcount
        databyte
        onecount
        ENDC


	; Vector for normal start up.
        org     0
        goto    start


; Main program starts here:
start   clrw			; Clear W.	
        movwf   GPIO            ; Ensure PORT is zero before we enable it.
        movlw	0xFD		; All inputs except GP1
        tris	GPIO

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Complete Source Code

Proteus Simulation

In Proteus VSM, the PIC10F202 is connected directly to a virtual RS232 terminal.
The terminal sends serial characters at a fixed baud rate, while the parity setting can be enabled or disabled.
When incorrect parity is transmitted, the LED turns on immediately, clearly showing how parity errors are detected in real time.
This setup makes it easy to experiment with different characters and parity configurations.

Conclusion

The PIC10 RS232 Parity Checker is a clean, educational example of implementing serial communication logic on a very small microcontroller.
It highlights how timing, bit manipulation, and parity checking work at a low level without relying on hardware peripherals.
Through Proteus simulation, learners can safely explore RS232 behavior and parity errors in a controlled environment.
This project delivers strong learning value for anyone interested in embedded systems, DIY electronics, and practical firmware design.

Complete File

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PIC10 RS232 Parity Checker using PIC10F202 with Proteus Simulation