# readPin

[Built-ins](README.md)

Canonical ID: `gpio.read`. Nederlands: `leesPin`.

A **pin** is a connection for a signal. **GPIO** means general-purpose input/output; **BCM** is the GPIO numbering scheme, not the order of pins on the connector. In the interpreter and browser these pins are **virtual**, with pretend states stored by Pliro. Only an explicit native Raspberry Pi target accesses physical pins. **Configure** means choose input or output before using a pin. See [GPIO and circuit words](../guides/gpio.md).

Reads a configured input level or the last successfully written logical value of a configured output. The result is Boolean. Reading does not configure a pin, wait for a transition, or return a voltage. Physical input requires a supported Pi target and access to the selected GPIO line.

## Signature

```text
readPin(pin)
```

## Arguments

| Parameter | Type | Requirement |
|---|---|---|
| `pin` | Number | Whole BCM GPIO number 0–27; not the physical connector position. |

## Return value

`Boolean`.

## Example

```pliro
# language: en
pinOutput(17)
writePin(17, true)
if readPin(17):
    say "Pliro"
writePin(17, false)
```

Prints `Pliro` and leaves the output low.

## Notes and common mistakes

Use the function name for your source language. Its [canonical ID](../concepts/canonical-identity.md) is a shared documentation label; you do not type that ID as a call. Giving your own variable or function the same name can hide the built-in. Supply the documented [arguments](../concepts/parameters-and-arguments.md) and value types. Pliro reports mismatches when checking can detect them, or when the call runs.

BCM numbers differ from physical header positions. Test in the virtual workbench before a physical Pi export. Follow the board manufacturer’s electrical guidance for resistors, pull-ups/pull-downs, and voltage levels. Missing physical capability or line access is reported as a diagnostic; an entitlement is not permission to access hardware.

## Related entries

[pinOutput](pinOutput.md) · [pinInput](pinInput.md) · [writePin](writePin.md) · [Programming guides](../guides/gpio.md) · [Host support](../guides/hosts.md) · [Calls and arguments](../syntax/calls.md)