against-device-time-offline-mode-any-device

lets go 💡...

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✅ Tujuan:

Membuat program untuk Raspberry Pi Pico (dengan RTC DS3231) agar:

• Pico bisa baca jam dari RTC.
• Pico bisa respon via serial (USB) saat Flutter (atau perangkat apa pun) minta waktu.
• Cocok untuk aplikasi offline mode anti manipulasi waktu.

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📦 Alat yang Dibutuhkan:

Alat	Keterangan
Raspberry Pi Pico	Bisa pakai Pico biasa (tanpa WiFi)
Modul RTC DS3231	Real Time Clock dengan baterai
Kabel Micro USB	Untuk koneksi ke HP/PC
Jumper kabel	Untuk menghubungkan Pico ↔ RTC

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🧠 Wiring RTC DS3231 ke Pico

DS3231     ↔️     Pico
------------------------
VCC        →     3.3V (pin 36)
GND        →     GND (pin 38)
SDA        →     GP0 (pin 1)
SCL        →     GP1 (pin 2)

Bisa juga pakai pin SDA/SCL lain, tapi ini yang umum.

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🔧 MicroPython Program (untuk Pico)

1. Siapkan firmware MicroPython ke Pico dulu (pakai Thonny).
2. Lalu upload script berikut sebagai main.py.

from machine import Pin, I2C
import time
import sys

# DS3231 class
class DS3231:
    def __init__(self, i2c):
        self.i2c = i2c
        self.address = 0x68

    def _bcd2dec(self, bcd):
        return (bcd // 16) * 10 + (bcd % 16)

    def get_time(self):
        data = self.i2c.readfrom_mem(self.address, 0x00, 7)
        second = self._bcd2dec(data[0])
        minute = self._bcd2dec(data[1])
        hour = self._bcd2dec(data[2])
        day = self._bcd2dec(data[4])
        month = self._bcd2dec(data[5] & 0x1F)
        year = self._bcd2dec(data[6]) + 2000
        return f"{year:04d}-{month:02d}-{day:02d}T{hour:02d}:{minute:02d}:{second:02d}Z"

# Setup I2C
i2c = I2C(0, scl=Pin(1), sda=Pin(0), freq=400_000)
rtc = DS3231(i2c)

# Main loop: listen via USB serial
while True:
    try:
        if sys.stdin in select.select([sys.stdin], [], [], 0)[0]:
            command = sys.stdin.readline().strip()
            if command == "yo_minta_jam":
                print(rtc.get_time())
    except:
        pass
    time.sleep(0.1)

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🔌 Uji Coba dari Komputer

Jika kamu sambung ke komputer, bisa pakai Serial Monitor (seperti Thonny, PuTTY, atau Arduino IDE):

1. Kirim teks: yo_minta_jam
2. Pico akan balas: 2025-07-08T13:14:30Z

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📲 Integrasi dengan Flutter (next step)

Flutter akan:

• Connect via usb_serial (Android)
• Kirim yo_minta_jam
• Terima timestamp YYYY-MM-DDTHH:MM:SSZ

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// maual set time for first time
def set_time(year, month, day, hour, minute, second):
    def dec2bcd(val):
        return (val // 10) << 4 | (val % 10)
    
    rtc_data = bytearray([
        dec2bcd(second),
        dec2bcd(minute),
        dec2bcd(hour),
        0,  # Day of week (0 = ignore)
        dec2bcd(day),
        dec2bcd(month),
        dec2bcd(year - 2000)
    ])
    i2c.writeto_mem(rtc.address, 0x00, rtc_data)

// # Misal sekarang 8 Juli 2025, jam 13:45:30
// set_time(2025, 7, 8, 13, 45, 30)
// check with rtc.get_time()

// kalau otomatis
// import time
// now = time.localtime()
// set_time(now[0], now[1], now[2], now[3], now[4], now[5])

💡 Bonus: Advanced Anti-Manipulation Tips

• Use checksums or digital signatures per data entry.
• Store boot time/power loss logs for auditing.
• Lock the RTC clock if needed (can only be set once during initial setup).

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