# Arnold — Terminator I/O Server

Fast-poll Modbus TCP server for AutomationDirect Terminator I/O systems.
Reads all digital inputs at 20 Hz, exposes a REST API for signal state,
and executes timed output sequences.

## Layout

```
server.py                   entrypoint — wires everything together
config.yaml                 edit this to describe your hardware
config_with_outputs.yaml    example with input + output modules
runs.log                    JSON-lines sequence run history (created at runtime)

arnold/
  config.py                 YAML loader, dataclasses, config validation
  terminator_io.py          Terminator I/O driver: Modbus TCP, signal cache, poll thread
  sequencer.py              Sequence execution engine
  api.py                    FastAPI REST application
```

## Quick start

```bash
pip3 install pymodbus fastapi uvicorn pyyaml --break-system-packages
python3 server.py                          # uses config.yaml, port 8000
python3 server.py --config config_with_outputs.yaml --log-level debug
```

Interactive API docs: `http://<pi-ip>:8000/docs`

## API

| Method | Path | Description |
|--------|------|-------------|
| GET | `/status` | Device comms health, poll rates, active sequence |
| GET | `/io` | All signal states (name → value/stale/updated_at) |
| GET | `/io/{signal}` | Single signal with device/slot/point/modbus_address |
| GET | `/sequences` | List sequences from config |
| GET | `/sequences/{name}` | Sequence detail with step list |
| POST | `/sequences/{name}/run` | Start a sequence → `{run_id}` (409 if one is running) |
| GET | `/runs/{run_id}` | Run result: pending/running/success/failed/error |
| GET | `/runs` | Recent run history (most recent first, `?limit=N`) |

## Config file

```yaml
devices:
  - id: ebc100_main
    host: 192.168.3.202
    port: 502           # default Modbus TCP port
    unit_id: 1          # EBC100 responds to any unit ID over TCP; use 1
    poll_interval_ms: 50
    modules:
      - slot: 1
        type: T1H-08TDS   # 8-pt 24VDC sinking input
        points: 8
      - slot: 3
        type: T1K-16TD2-1 # 16-pt sourcing output
        points: 16

logical_io:
  - name: sensor_a
    device: ebc100_main
    slot: 1
    point: 1
    direction: input
  - name: valve_1
    device: ebc100_main
    slot: 3
    point: 1
    direction: output

sequences:
  - name: actuate
    description: "Open valve, verify sensor, close valve"
    steps:
      - { t_ms:    0, action: set_output,  signal: valve_1,  state: true  }
      - { t_ms:  500, action: check_input, signal: sensor_a, expected: true }
      - { t_ms: 1000, action: set_output,  signal: valve_1,  state: false }
```

**Timing:** `t_ms` is absolute from sequence T=0 (not relative delays).
Steps are sorted by `t_ms` at load time; order in the file doesn't matter.
Multiple steps with the same `t_ms` execute in file order.

**Failure:** a failed `check_input` aborts the sequence immediately.
Remaining steps — including output resets — are skipped.
Add an explicit reset sequence (`all_outputs_off`) and call it after a failure.

## Supported module types

| Type | Direction | Points |
|------|-----------|--------|
| T1H-08TDS, T1K-08TDS | input | 8 |
| T1H-08ND3, T1K-08ND3 | input | 8 |
| T1H-16ND3, T1K-16ND3 | input | 16 |
| T1H-08NA, T1K-08NA | input | 8 |
| T1H-08TD1, T1K-08TD1 | output | 8 |
| T1H-08TD2, T1K-08TD2 | output | 8 |
| T1H-16TD1, T1K-16TD1 | output | 16 |
| T1H-16TD2, T1K-16TD2, T1K-16TD2-1 | output | 16 |
| T1H-08TA, T1K-08TA | output | 8 |
| T1H-08TRS, T1K-08TRS | output | 8 |

## T1H-EBC100 hardware quirks

### Unified coil address space

The EBC100 maps **all modules — inputs and outputs — into a single flat
address space** ordered by physical slot number.  There is no separate
"input base address" and "output base address".

Example: slot 1 = 8-pt input, slot 2 = 8-pt input, slot 3 = 16-pt output:

| Slot | Module | Points | Coil addresses |
|------|--------|--------|----------------|
| 1 | T1H-08TDS (input) | 8 | 0–7 |
| 2 | T1H-08TDS (input) | 8 | 8–15 |
| 3 | T1K-16TD2-1 (output) | 16 | **16–31** |

FC05/FC15 output writes must use these unified addresses.
The config loader computes `modbus_address` for every module and signal
automatically — you never write raw addresses in YAML.

### FC02 input reads start at address 0

FC02 (read discrete inputs) returns only input bits, starting at bit index 0,
regardless of where inputs sit in the unified space.  The poll thread reads
`total_input_points` bits from FC02 address 0.  Because `modbus_address` for
input signals equals their FC02 bit index (inputs occupy the lowest slots in
practice), no remapping is needed.

### No exception on out-of-range addresses

The EBC100 returns zeros for any FC02 read address beyond the installed
modules — it never raises Modbus exception code 2 (illegal data address).
Module presence **cannot** be auto-detected from protocol errors.
The `modules` list in the config is authoritative.

### FC05 write echo

`write_coil` (FC05) echoes back `True` for any address, even unmapped ones.
There is no error feedback for writes to non-existent output points.
Config validation at startup prevents invalid addresses from being used.

### Unit ID is ignored

The EBC100 accepts and echoes back any Modbus unit/slave ID over TCP.
Set `unit_id: 1` in the config (standard default).

### No unsolicited push

Modbus TCP is a strictly polled protocol; the EBC100 has no push capability.
The server polls at `poll_interval_ms` (default 50 ms = 20 Hz).
At 24 input points a single FC02 read takes ~1 ms on a local network.

### Web interface

The EBC100 hosts a minimal HTTP server on port 80 (firmware by Host Engineering).
It exposes IP/subnet/gateway config and serial port mode only — no I/O data.
Port 443, 503, and 8080 are closed.  UDP port 502 is not active.