#!/usr/bin/env python3
import time
from smbus2 import SMBus

ADDR = 0x48  # change if your i2cdetect shows a different one
REG_CONV = 0x00
REG_CFG  = 0x01

# PGA gain bits: +/-4.096V gives 0.125mV/LSB (nice for small signals)
PGA_4_096 = 0x0200

# 128 SPS is stable; can bump to 250/475 later
DR_128SPS = 0x0080

# Single-shot mode
MODE_SINGLE = 0x0100

# Comparator disabled
COMP_DISABLE = 0x0003

# MUX values (ADS1115)
MUX_SE = {
    0: 0x4000,  # AIN0 vs GND
    1: 0x5000,
    2: 0x6000,
    3: 0x7000,
}
# Differential pairs we care about when 4 unknown wires go to A0-A3
MUX_DIFF = {
    "D01": 0x0000,  # A0-A1
    "D03": 0x1000,  # A0-A3
    "D13": 0x2000,  # A1-A3
    "D23": 0x3000,  # A2-A3
    "D02": 0x4000,  # A0-A2
    "D12": 0x5000,  # A1-A2
}

# LSB for PGA +/-4.096V is 125uV
LSB_V = 0.000125

def write_u16(bus, reg, value):
    # ADS expects big-endian
    bus.write_i2c_block_data(ADDR, reg, [(value >> 8) & 0xFF, value & 0xFF])

def read_u16(bus, reg):
    data = bus.read_i2c_block_data(ADDR, reg, 2)
    return (data[0] << 8) | data[1]

def read_signed_conv(bus):
    raw = read_u16(bus, REG_CONV)
    # Convert to signed 16-bit
    if raw & 0x8000:
        raw -= 1 << 16
    return raw

def read_channel(bus, mux_bits):
    cfg = mux_bits | PGA_4_096 | MODE_SINGLE | DR_128SPS | COMP_DISABLE
    # Start conversion by setting OS bit
    cfg |= 0x8000
    write_u16(bus, REG_CFG, cfg)

    # Wait for conversion: at 128SPS max ~7.8ms; give it 10ms
    time.sleep(0.010)
    raw = read_signed_conv(bus)
    return raw * LSB_V

def fmt_mv(v):
    return f"{v*1000:7.1f}mV"

def main():
    print("ADS1115 scan - Ctrl+C to stop")
    print("Tip: floating inputs drift. For clean 'unplug goes near 0 fast', add 470k-1M pulldown from each A0-A3 to GND.")
    with SMBus(1) as bus:
        while True:
            se = {ch: read_channel(bus, MUX_SE[ch]) for ch in range(4)}
            d  = {name: read_channel(bus, mux) for name, mux in MUX_DIFF.items()}

            line = (
                f"SE0:{fmt_mv(se[0])} SE1:{fmt_mv(se[1])} SE2:{fmt_mv(se[2])} SE3:{fmt_mv(se[3])} | "
                f"D01:{fmt_mv(d['D01'])} D02:{fmt_mv(d['D02'])} D03:{fmt_mv(d['D03'])} "
                f"D12:{fmt_mv(d['D12'])} D13:{fmt_mv(d['D13'])} D23:{fmt_mv(d['D23'])}"
            )
            print(line)
            time.sleep(0.05)  # 20Hz-ish

if __name__ == "__main__":
    main()