> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lagerdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# DAC

> Set and read back an analog output voltage

Drive an analog output voltage into your DUT from a DAC net.

## Handle

```rust theme={null}
use lager::LagerBox;

let lager = LagerBox::from_env()?;
let dac = lager.dac("dac1");
```

## Methods

| Method   | Description                          |
| -------- | ------------------------------------ |
| `name()` | The net name this handle addresses   |
| `set()`  | Set the output voltage in volts      |
| `read()` | Read back the current output voltage |

## Method Reference

### `name() -> &str`

The net name this handle was created with.

### `set(volts: f64) -> Result<()>`

Set the output voltage.

```rust theme={null}
dac.set(1.8)?;
```

**Parameters:**

| Parameter | Type  | Description                    |
| --------- | ----- | ------------------------------ |
| `volts`   | `f64` | Target output voltage in volts |

### `read() -> Result<f64>`

Read back the voltage the DAC is currently outputting.

```rust theme={null}
let v = dac.read()?;
```

**Returns:** `f64` — the output voltage in volts.

<Warning>
  Not every DAC supports readback. On an MCC USB-202 this call fails with
  `Error::Box` and the message `USB-202 does not support DAC output readback`.
  Where you need a verified output, measure it with an ADC net instead of trusting
  `read()` to exist.
</Warning>

## Examples

### Sweep a reference and check the DUT tracks it

```rust theme={null}
let dac = lager.dac("dac1");
let sense = lager.adc("adc1");

for target in [0.0_f64, 0.5, 1.0, 1.5, 2.0] {
    dac.set(target)?;
    std::thread::sleep(std::time::Duration::from_millis(50));
    let measured = sense.read()?;
    assert!((measured - target).abs() < 0.05,
            "set {target:.2} V, measured {measured:.4} V");
}
dac.set(0.0)?;
```

## Supported Hardware

| Instrument  | Channels   | Readback      |
| ----------- | ---------- | ------------- |
| LabJack T7  | DAC0, DAC1 | Supported     |
| MCC USB-202 | DAC0, DAC1 | Not supported |

## Notes

* Leave the output where the next test expects it. A DAC holds its last value after
  your test ends; setting it back to `0.0` in teardown is usually right.
* Output accuracy is the instrument's, not the API's. A LabJack T7 asked for 1.0 V
  reads back around 0.99995 V, which is the DAC's resolution rather than an error.