[EN] RTC PCF8583

From a Python article on how to use pcf8583 as an RTC (Real-time clock) board, we have rewritten the code for Arduino’s C++ programming with esp8266, esp32 and stm32.

Example Code

An example program for using PCF8583 by designing a method similar to the previous article is

1. bool found() for checking the status of whether there is a PCF8583 board installed on the system bus or not.
2. _write( ) for writing data.
3. now() for reading time from PCF8583 to store in rtc variable.
4. adjust( ) for setting up PCF8583.
5. show( ) for displaying values from rtc variables to serial communication port.

The code:

#include <Wire.h>

#define RTC_CTRL 0x00
#define RTC_SEC_100 0x01
#define RTC_SEC 0x02
#define ALM_CTRL 0x08
#define RTC_YEAR_MEM_ADDR 0x20
#define RTC_BEGIN_YEAR 2020

uint8_t dec2bcd(uint8_t n) { 
// แปลงเลขฐาน 10 เป็นรหัส BCD
  return (((uint8_t)(n / 10) * 16) + (n % 10));
}

uint8_t bcd2dec(uint8_t n) {
// แปลงรหัส BCD เป็นตัวเลขฐาน 10
  return (((uint8_t)(n / 16) * 10) + (n % 16)); 
}

char dayOfWeek[][4] = {"sun", "mon", "tue", "wed", "thu", "fri", "sat"};

class PCF8583 {
  private:
    uint8_t addr;
    uint8_t rtc[8];
    uint16_t beginYear;
  public:
    PCF8583(uint8_t _addr = 81) {
      addr = _addr;
      beginYear = RTC_BEGIN_YEAR;
    }
    void _write(uint8_t ctrl, uint8_t value) {
      Wire.beginTransmission( addr );
      Wire.write( ctrl );
      Wire.write( value );
      Wire.endTransmission();

    }
    void begin() {
      _write(RTC_CTRL, 0x00);
      _write(ALM_CTRL, 0x00);
      // บันทึกค่าปีเริ่มต้นในหน่วยความจำ
      _write(RTC_YEAR_MEM_ADDR, (uint8_t)(beginYear & 0x00FF));
      _write(RTC_YEAR_MEM_ADDR + 1, (uint8_t)(beginYear >> 8));
    }

    bool found() {
      Wire.beginTransmission( addr );
      if (Wire.endTransmission() == 0) {
        return true;
      }
      return false;
    }

    void now() {
      uint8_t buff[5];
      int idx = 0;

      Wire.beginTransmission( addr );
      Wire.write( RTC_YEAR_MEM_ADDR );
      Wire.endTransmission();
      // อ่านค่าปีที่เก็บไว้
      Wire.requestFrom(addr, 2);
      idx = 0;
      while (Wire.available()) {
        buff[idx] = Wire.read();
        idx++;
      }
      beginYear = buff[1] << 8;
      beginYear += buff[0];
      // อ่านข้อมูลจาก PCF8583
      Wire.beginTransmission( addr );
      Wire.write( RTC_SEC );
      Wire.endTransmission();
      Wire.requestFrom(addr, 5);
      idx = 0;
      while (Wire.available()) {  // slave may send less than requested
        buff[idx] = Wire.read();    // receive a byte as character
        idx++;
      }
      // แปลงข้อมูลมาเก็บไว้ในตัวแปร rtc
      rtc[0] = bcd2dec(buff[0]); // second
      rtc[1] = bcd2dec(buff[1]); // minute
      rtc[2] = bcd2dec(buff[2]); // hour
      rtc[3] = bcd2dec(buff[3] & 0x3f); // day
      rtc[4] = bcd2dec(buff[4] & 0x1f); // month
      rtc[5] = (buff[3] >> 6); // year
      rtc[6] = buff[4] >> 5; // day of week
    }

    void show() {
      Serial.print(dayOfWeek[rtc[6]]);
      Serial.print(". ");
      Serial.print(rtc[3]);
      Serial.print("/");
      Serial.print(rtc[4]);
      Serial.print("/");
      Serial.print(rtc[5]+beginYear);
      Serial.print(" ");
      Serial.print(rtc[2]);
      Serial.print(":");
      Serial.print(rtc[1]);
      Serial.print(":");
      Serial.print(rtc[0]);
      Serial.println(" ");
    }

    void adjust(uint8_t day, uint8_t month, uint16_t year,
    uint8_t dow, 
    uint8_t hour, uint8_t minute, uint8_t second) {
      uint8_t y = (year-RTC_BEGIN_YEAR)<<6;
      uint8_t d = dow<<5;
      Wire.beginTransmission( addr );
      Wire.write( RTC_SEC );
      Wire.write( dec2bcd(second) );
      Wire.write( dec2bcd(minute) );
      Wire.write( dec2bcd(hour) );
      Wire.write( dec2bcd(day)+y );
      Wire.write( dec2bcd(month)+d );
      Wire.endTransmission();
    }
};

PCF8583 rtc;

void setup() {
  Serial.begin(115200);
  Serial.println("\n------------------\n");
  Wire.begin();
  if (rtc.found()) {
    rtc.begin();
    Serial.println("Found PCF8583");
    rtc.adjust(4,7,2021,0,21,20,0); // ตั้งเวลาใหม่ (อย่าลืมเปลี่ยนนะครับ)
  } else {
    Serial.println("Not found PCF8583");
    while(true);
  }
}

void loop() {
  rtc.now();
  rtc.show();
  delay(1000);
}

Conclusion

From this article, you will find that if you understand programming principles, you will be able to transcode between different languages. So you should concerned about how to understand the working principle of the device by studying the documentation for that device. Finally, have fun with programming.

If you want to talk with us, feel free to leave comments below!!

Reference

1. ET-MINI PCF8583

(C) 2020-2021, By Jarut Busarathid and Danai Jedsadathitikul
Updated 2021-10-18