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import time
import smbus
from collections import deque
import matplotlib.pyplot as plt

BUS=1
ADDR=0x48
REG_CONV=0x00
REG_CONFIG=0x01

bus = smbus.SMBus(BUS)

# Continuous, AIN0, PGA ±4.096V, 860 SPS (chip side)
config = 0x8000 | 0x4000 | 0x0200 | 0x0000 | 0x00E0 | 0x0003
bus.write_i2c_block_data(ADDR, REG_CONFIG, [(config>>8)&0xFF, config&0xFF])

FS_VOLTS = 4.096

def read_volts():
    data = bus.read_i2c_block_data(ADDR, REG_CONV, 2)
    raw = (data[0]<<8) | data[1]
    if raw & 0x8000:
        raw -= 1<<16
    return raw * FS_VOLTS / 32768.0

WINDOW_SECONDS = 0.5
ts = deque()
vs = deque()

plt.ion()
fig, ax = plt.subplots()
line, = ax.plot([], [])
ax.set_title("ADS1115 AIN0 live (real-time window)")
ax.set_xlabel("Time (s)")
ax.set_ylabel("Volts")
ax.set_ylim(-0.5, 3.5)

last_draw = time.perf_counter()
draw_interval = 1/30

t_start = time.perf_counter()

while True:
    v = read_volts()
    t = time.perf_counter() - t_start

ts.append(t)
    vs.append(v)

# keep only last WINDOW_SECONDS
    while ts and (ts[-1] - ts[0]) > WINDOW_SECONDS:
        ts.popleft()
        vs.popleft()

now = time.perf_counter()
    if now - last_draw >= draw_interval:
        # x-axis is "time relative to last point"
        t0 = ts[-1]
        xs = [ti - t0 for ti in ts]   # ends at 0
        line.set_data(xs, list(vs))
        ax.set_xlim(-WINDOW_SECONDS, 0)
        fig.canvas.draw_idle()
        plt.pause(0.001)
        last_draw = now

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