# Bar-graph level indicator

A Python version of the Structured Text example in [Analog Threshold Control](../../../programming/examples/analog-threshold-control.md). The thresholds are spaced evenly across the input span instead of at 2, 4, 6 and 7.9 V. This version carries none of the guarantees the PLC runtime provides.

```python
#!/usr/bin/env python3
"""Light 0-4 outputs in proportion to a 0-10 V input."""

import signal
import time

import synergy_logic

base = synergy_logic.Base()
base.rollCall(["SLM-AI-8-V", "SLM-DCO-15P"])

level_in = base[1][1]
outputs = base[2]

INPUT_MAX = 8191      # 13-bit analog input, native resolution
SEGMENTS = 4
MARGIN = 41           # a little headroom so full scale reliably lights all four

running = True

def shutdown(signum, frame):
    global running
    running = False

signal.signal(signal.SIGTERM, shutdown)
signal.signal(signal.SIGINT, shutdown)

try:
    while running:
        counts = level_in.value
        span = INPUT_MAX - MARGIN
        lit = min(int(counts / span * SEGMENTS), SEGMENTS)

        mask = (1 << lit) - 1     # 0 -> 0b0000, 3 -> 0b0111
        outputs.do_bitmapped(mask)

        print(f"{counts:5d} counts  {level_in.real:5.2f} V  {lit} lit")
        time.sleep(0.1)
finally:
    outputs.do_bitmapped(0)
```

`(1 << lit) - 1` builds the bit pattern directly, so three lit segments give `0b0111`. A single bus transaction sets all of them.