# NI-9477 digital output module

Flowchem supports the National Instruments NI-9477 C Series module when it is installed in a CompactDAQ chassis such as
the cDAQ-9171. The NI-9477 is exposed as a 32-channel relay-style component named `relay`.

```{note}
The NI-9477 is a sinking digital output module. In Flowchem, `power-on` means that the output line is active/sinking
current. It does not mean the module sources voltage to the connected load.
```

## Installation

Install the NI-DAQmx driver from NI and confirm the chassis and module are visible in NI MAX. Then install Flowchem with
the NI extra:

```shell
python -m pip install "flowchem[ni]"
```

For local development from this repository:

```shell
python -m pip install -e ".[ni]"
```

## Configuration

If there is exactly one NI-9477 visible to NI-DAQmx, `module` may be omitted. Otherwise, set it to the NI MAX module
name, for example `cDAQ1Mod1` or `Dev1`.

```toml
[device.ni_outputs]
type = "NI9477"
module = "cDAQ1Mod1"
reset_outputs_on_initialize = true
```

By default, Flowchem writes all 32 outputs OFF during initialization so the cached output state is known. Set
`reset_outputs_on_initialize = false` if startup must not modify the hardware state.

## Relay API

The component is available as `device_name/relay`, for example `ni_outputs/relay`.

* `PUT /power-on?channel=1` activates one output.
* `PUT /power-off?channel=1` deactivates one output.
* `GET /is-on?channel=1` returns whether one output is active.
* `PUT /multiple_channel?values=101` sets outputs from a compact state string; missing channels are padded OFF.
* `GET /channel_set_point?channel=1` returns `1` or `0` for one output.
* `GET /channels_set_point` returns all 32 cached output states.

Flowchem channels are numbered `1` to `32`, mapped to NI physical lines `line0` to `line31`.

## Controlling a solenoid valve

The NI relay component can be used as a `support_platform` for a BioChem solenoid valve:

```toml
[device.ni_outputs]
type = "NI9477"
module = "cDAQ1Mod1"

[device.valve_1]
type = "BioChemSolenoidValve"
support_platform = "ni_outputs/relay"
channel = 1
normally_open = false
```

The `channel` value selects which NI-9477 output line drives the valve.