RFremote_decoder

A lightweight library for decoding EV1527, HS1527 RF remote 433/315 MHz signals using GPIO_EXTI and timer counter. Originally written for STM32F103, but easily portable to other microcontrollers.

📡 Overview

• Supports 433 MHz RF transmitters based on the EV1527 protocol.
• Decodes 24-bit Remote ID + 2-bit Command.
• Interrupt-based, non-blocking design.
• Written for STM32F103 (HAL/LL), but easy to port to other MCUs.

🔧 Porting

To port this library to a different microcontroller, you need to adapt:

• GPIO input: to connect the RF receiver's data pin.
• EXTI (External Interrupt): to capture signal edges.
• Timer: to measure pulse durations.

⚠️ Caution

Timing accuracy is critical! Make sure your timer resolution is sufficient to distinguish between logic '0' and '1' pulse lengths in the EV1527 protocol.

• Timer frequency: at least 1 MHz (1 µs resolution).
• My SystemCoreClock is max 72 MHz because processing in the interrupt routine should finish before the next interrupt arrives.

🚀 Usage

🔧 Interrupt Handler

void EXTI3_IRQHandler(void)
{
  /* USER CODE BEGIN EXTI3_IRQn 0 */

  if (LL_EXTI_IsActiveFlag_0_31(LL_EXTI_LINE_3) != RESET)
  {
    LL_EXTI_ClearFlag_0_31(LL_EXTI_LINE_3);
    
    uint32_t cnt = timer_counter_getValue();
    timer_counter_reset();
    bool edgeType = LL_GPIO_IsInputPinSet(GPIOA, LL_GPIO_PIN_3);
    RFremote_callBack(cnt, edgeType);
  }

}

🔧 Main

#include "RFremote.h"

RFremotePacket_t packet;

if (RFremote_getPacket(&packet))
{
    printf("Remote ID: %d, CMD: %d\n", packet.remoteID, packet.remoteCMD);
}

🧠 EV1527

• Signal stream starts with a preamble, followed by 24 bits of data: the 2 least significant bits are command bits, and the rest is a unique remote ID.

• resistor conncected to oscillator pin of EV1527 afect on pulse length.
• worst case is 3.01ms for whole packet
• whole packet size is: (31+1) + 24(3+1) = 128 pulses
• 3.01ms / 128 = 10us --->> so this is why 1MHz ~ 1us timer is sutable

💡 Advice:

Use a logic analyzer for better insight.