cat > ads_scope.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=4.096
def read_v():
    raw = bus.read_word_data(ADDR, REG_CONV)
    raw = ((raw & 0xFF) << 8) | (raw >> 8)
    if raw & 0x8000:
        raw -= 1<<16
    return raw * FS / 32768.0

# ---- Tuning knobs ----
WINDOW_SECONDS = 0.5      # how much time you want visible
ASSUMED_SPS = 860         # ADS max conversion rate
DRAW_FPS = 25             # how often we redraw (UI)
DECIM = 4                 # show 1 in N samples (reduces "cramped" look + speeds UI)

# Display buffer size: window * (sps/decim)
disp_sps = ASSUMED_SPS // DECIM
N = int(WINDOW_SECONDS * disp_sps)
ys = deque([0.0]*N, maxlen=N)

plt.ion()
fig, ax = plt.subplots()
xs = [i / disp_sps for i in range(N)]
line, = ax.plot(xs, list(ys))
ax.set_title(f"ADS1115 AIN0 scope ({WINDOW_SECONDS}s window, ~{disp_sps} pts/s shown)")
ax.set_xlabel("Time (s)")
ax.set_ylabel("Volts")
ax.set_xlim(0, WINDOW_SECONDS)
ax.set_ylim(-0.5, 3.5)

# Make redraw cheap
fig.canvas.draw()
bg = fig.canvas.copy_from_bbox(ax.bbox)

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

# Rate meters
last_rate_t = time.perf_counter()
read_count = 0
append_count = 0
decim_counter = 0

while True:
    v = read_v()
    read_count += 1
    decim_counter += 1

    # keep only 1 out of DECIM reads for display
    if decim_counter >= DECIM:
        ys.append(v)
        append_count += 1
        decim_counter = 0

    now = time.perf_counter()

    # Print rates once per second
    if now - last_rate_t >= 1.0:
        dt = now - last_rate_t
        print(f"reads/sec={read_count/dt:.0f}  plotted_points/sec={append_count/dt:.0f}")
        last_rate_t = now
        read_count = 0
        append_count = 0

    # Redraw at DRAW_FPS
    if now - last_draw >= draw_interval:
        line.set_ydata(list(ys))
        fig.canvas.restore_region(bg)
        ax.draw_artist(line)
        fig.canvas.blit(ax.bbox)
        fig.canvas.flush_events()
        last_draw = now
PY
python3 ads_scope.py