# NI-6519 digital I/O

Flowchem supports the National Instruments NI-6519 industrial digital I/O device through NI-DAQmx. The NI-6519 is
exposed as two components:

* `relay`: the 16 digital outputs on `P2.0` to `P2.7`, then `P3.0` to `P3.7`.
* `digital-input`: the 16 digital inputs on `P0.0` to `P0.7`, then `P1.0` to `P1.7`.

The port directions are fixed by the NI-6519 hardware and do not need to be configured.

```{note}
The NI-6519 outputs are sinking outputs. Wire the output supply to `OUT.COM (VCC)` and ground to `GND` according to
the NI 651x manual.
```

## Configuration

```toml
[device.valve_io]
type = "NI6519"
module = "Dev1"
reset_outputs_on_initialize = true
```

If there is exactly one NI-6519 visible to NI-DAQmx, `module` may be omitted. Otherwise, set it to the NI MAX device
name.

## API

The relay component is available as `valve_io/relay`:

* `PUT /power-on?channel=1` activates output channel 1.
* `PUT /power-off?channel=1` deactivates output channel 1.
* `GET /is-on?channel=1` returns the cached output state.
* `PUT /multiple_channel?values=101` sets all 16 outputs from a compact state string.
* `GET /channels_set_point` returns all cached output states.

The digital input component is available as `valve_io/digital-input`:

* `GET /read?channel=1` reads one input.
* `GET /read_all` reads all 16 inputs.