# fake

The `fake` board returns incrementing values for digital interrupt ticks and analogs.

Configure a `fake` board to test integrating a board into your machine without physical hardware:

- [JSON Template](https://docs.viam.com/reference/components/board/fake/#configure-an-fake-board-0)

```json

```

The following attributes are available for `fake` boards:

| Name                  | Type    | Required?    | Description                                                                                 |
|-----------------------|---------|---------------|---------------------------------------------------------------------------------------------|
| `fail_new`           | bool    | **Required**  | If the fake board should raise an error at machine start-up.                              |
| `analogs`            | object  | Optional      | Attributes of any pins that can be used as Analog-to-Digital Converter (ADC) inputs. See [configuration info](https://docs.viam.com/reference/components/board/fake/#analogs). |
| `digital_interrupts`  | object  | Optional      | Pin and name of any digital interrupts. See [configuration info](https://docs.viam.com/reference/components/board/fake/#digital_interrupts). |

## Attribute configuration

Configuring these attributes on your board allows you to integrate [analog-to-digital converters](https://docs.viam.com/reference/components/board/fake/#analogs) and [digital interrupts](https://docs.viam.com/reference/components/board/fake/#digital_interrupts) into your machine.

### `analogs`

An [analog-to-digital converter](https://www.electronics-tutorials.ws/combination/analogue-to-digital-converter.html) (ADC) takes a continuous voltage input (analog signal) and converts it to an discrete integer output (digital signal).

ADCs are useful when building a robot, as they enable your board to read the analog signal output by most types of [sensors](https://docs.viam.com/reference/components/sensor/) and other hardware components.

To integrate an ADC into your machine, you must first physically connect the pins on your ADC to your board.

Then, integrate `analogs` into the `attributes` of your board by following the **Config Builder** instructions or by adding the following to your board’s JSON configuration:

- [Config Builder](https://docs.viam.com/reference/components/board/fake/#configure-an-analog-reader-0)
- [JSON Template](https://docs.viam.com/reference/components/board/fake/#configure-an-analog-reader-1)
- [JSON Example](https://docs.viam.com/reference/components/board/fake/#configure-an-analog-reader-2)

On your board’s panel, click **Show more**, then select **Add analog**. Assign a name to your analog and then fill in the required properties outlined below.

```json

```

```json

```

The following properties are available for `analogs`:

| Name            | Type    | Required?    | Description                                                        |
|-----------------|---------|---------------|--------------------------------------------------------------------|
| `name`          | string  | **Required**  | Your name for the analog reader.                                   |
| `pin`           | string  | **Required**  | The pin number of the ADC’s connection pin, wired to the board. This should be labeled as the physical index of the pin on the ADC. |
| `chip_select`   | string  | **Required**  | The chip select index of the board’s connection pin, wired to the ADC. |
| `spi_bus`       | string  | **Required**  | The index of the SPI bus connecting the ADC and board.           |
| `average_over_ms` | int    | Optional      | Duration in milliseconds over which the rolling average of the analog input should be taken. |
| `samples_per_sec` | int    | Optional      | Sampling rate of the analog input in samples per second.           |

#### Test `analogs`

Once you have configured your analogs, open the board’s **TEST** panel on the **CONFIGURE** or [**CONTROL**](https://docs.viam.com/monitor/default-interface/#web-ui) tabs to monitor analogs. The numbers displayed next to each analog name represent the digital signal received from the analog inputs.

### `digital_interrupts`

[Interrupts](https://en.wikipedia.org/wiki/Interrupt) are a method of signaling precise state changes.
Configuring digital interrupts to monitor GPIO pins on your board is useful when your application needs to know precisely when there is a change in GPIO value between high and low.

- When an interrupt configured on your board processes a change in the state of the GPIO pin it is configured to monitor, it ticks to record the state change.
You can stream these ticks with the board API’s [`StreamTicks()`](https://docs.viam.com/reference/apis/components/board/#streamticks), or get the current value of the digital interrupt with [`Value()`](https://docs.viam.com/reference/apis/components/board/#getdigitalinterruptvalue).
- Calling [`GetGPIO()`](https://docs.viam.com/reference/apis/components/board/#getgpio) on a GPIO pin, which you can do without configuring interrupts, is useful when you want to know a pin’s value at specific points in your program, but is less precise and convenient than using an interrupt.

Integrate `digital_interrupts` into your machine in the `attributes` of your board by following the **Config Builder** instructions, or by adding the following to your board’s JSON configuration:

- [Config Builder](https://docs.viam.com/reference/components/board/fake/#configure-a-digital-interrupt-0)
- [JSON Template](https://docs.viam.com/reference/components/board/fake/#configure-a-digital-interrupt-1)
- [JSON Example](https://docs.viam.com/reference/components/board/fake/#configure-a-digital-interrupt-2)

On your board’s panel, click **Show more**, then select **Add digital interrupt**. Assign a name to your digital interrupt and then enter a pin number.

```json

```

```json

```

The following properties are available for `digital_interrupts`:

| Name                 | Type    | Required?    | Description                                                   |
|----------------------|---------|---------------|---------------------------------------------------------------|
| `name`               | string  | **Required**  | Your name for the digital interrupt.                          |
| `pin`                | string  | **Required**  | The pin number of the board’s GPIO pin that you wish to configure the digital interrupt for. |

#### Test `digital_interrupts`

Once you have configured your digital interrupts, open the board’s **TEST** panel on the **CONFIGURE** or [**CONTROL**](https://docs.viam.com/monitor/default-interface/#web-ui) tabs to monitor interrupt activity. The value displayed next to each interrupt name represents the total count of interrupts triggered by the corresponding digital interrupt.