cat > ads_plot_polling.py <<'PY'
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 mode, 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_fast():
    # Often faster than read_i2c_block_data
    raw = bus.read_word_data(ADDR, REG_CONV)
    raw = ((raw & 0xFF) << 8) | (raw >> 8)  # swap endian
    if raw & 0x8000:
        raw -= 1 << 16
    return raw * FS_VOLTS / 32768.0

WINDOW_SECONDS = 0.5          # rolling window shown
SAMPLE_SLEEP = 0.0            # set to 0.01 if you want ~100Hz like your raw script
DRAW_FPS = 30

ts = deque()
vs = deque()

plt.ion()
fig, ax = plt.subplots()
line, = ax.plot([], [])
ax.set_title("ADS1115 AIN0 live (polling, real-time window)")
ax.set_xlabel("Time (s)")
ax.set_ylabel("Volts")
ax.set_ylim(-0.5, 3.5)
ax.set_xlim(-WINDOW_SECONDS, 0)

t0 = time.perf_counter()
last_draw = t0
draw_interval = 1.0 / DRAW_FPS

# rate meter
last_rate_t = t0
rate_count = 0

while True:
    v = read_volts_fast()
    t = time.perf_counter() - t0
    ts.append(t)
    vs.append(v)
    rate_count += 1

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

    now = time.perf_counter()

    # print real sample rate once/sec
    if now - last_rate_t >= 1.0:
        sps = rate_count / (now - last_rate_t)
        print(f"Actual read rate: {sps:.1f} samples/sec")
        last_rate_t = now
        rate_count = 0

    # redraw at DRAW_FPS
    if now - last_draw >= draw_interval and len(ts) >= 2:
        t_end = ts[-1]
        xs = [ti - t_end 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

    if SAMPLE_SLEEP > 0:
        time.sleep(SAMPLE_SLEEP)
PY
python3 ads_plot_polling.py