# FieldSystemInterface — Interfaces

## Configuration

The service reads a JSON configuration file mounted at
`/etc/edd/field_system_interface/config.json`. The file is rendered from the Jinja2 template
in `roles/field_system_interface/templates/config.json.j2` at provision time.

| Parameter | Default | Description |
|---|---|---|
| `dbbc_port` | 5000 | TCP port of the DBBC control server |
| `mark5_port` | 2620 | TCP port of the Mark5b recorder |
| `katcp_port` | 7150 | KATCP server port of this service |
| `master_controller_host` | first host in `mastercontroller` group | EDD Master Controller address |
| `master_controller_port` | 7147 | EDD Master Controller KATCP port |
| `n_if` | 4 | Number of IF channels to monitor |
| `n_bbc` | 16 | Number of BBC channels to monitor |
| `command_timeout` | 10.0 s | Timeout for DBBC/Mark5 commands |
| `sensor_cache_ttl` | 1.0 s | Sensor value cache lifetime |
| `data_store.ip` | Redis host | Redis data store address |
| `data_store.port` | Redis port | Redis data store port |

## External Connections

| System | Protocol | Direction | Port |
|---|---|---|---|
| DBBC hardware | TCP (DBBC control protocol) | outbound | 5000 |
| Mark5b recorder | TCP (MK5 protocol) | outbound | 2620 |
| EDD Master Controller | KATCP | outbound | 7147 |
| EDD system | KATCP server | inbound | 7150 |
| Redis | TCP | outbound | redis\_port |

## POSIX Message Queue

The service writes recording start/stop messages to the VDIFPacker's POSIX message queue
(`mq_control`) when the Field System initiates a scan.

## KATCP Interface

The service exposes a KATCP server on port 7150 and publishes sensors derived from the DBBC
and Mark5b state. Exact sensor names depend on the number of IFs and BBCs configured.