IOCAN

# RBC Input

## Overview

An **RBC Input** decodes a **Reflected Binary Code** — better known as

[**Gray code**](https://en.wikipedia.org/wiki/Gray_code) — from a set of single-bit

inputs into an ordinary integer.

Gray code is an encoding where consecutive values differ by only **one** bit. It is

common on absolute rotary/position encoders and gear-position selectors because

only one line changes at a time, so the reading never glitches through a wrong

value while the switch moves between positions.

Each listed input supplies one bit of the Gray code; the input converts the whole

set to a plain binary number you can act on.

## Prerequisites

- The **source inputs** that supply the bits — usually

  [Digital Inputs](Digital-Input.md), one per encoder/switch line. Create them

  first.

- Each source is read as a bit: a non-zero value is `1`, zero is `0`.

- Know the **order** of the lines from most- to least-significant bit.

## Add it in the app

1. Add a new input and choose **RBC Input** as the type.

2. Give it a clear **alias** (e.g. `Gear Position`).

3. Add the **bit inputs** in order, most-significant bit first.

4. Check the decoded number against each physical switch position.

## Settings reference

| Setting | Meaning | Unit | Range / values | Notes |

|---|---|---|---|---|

| **Bit inputs** | Ordered list of single-bit inputs forming the Gray code | — | list of input ids (uint32) | Each input is one bit. The **list order** sets bit significance; the input converts the Gray code to a binary value. |

**Gray → binary:** the most-significant bit is taken as-is; each lower binary bit

is the running XOR of the higher binary bit with the next Gray bit. The result is

the ordinary integer (e.g. an 8-position encoder decodes to `0`–`7`). If the value

counts the wrong way for your wiring, reverse the order the inputs are listed in.

## Common settings

RBC Input also uses the shared setting — alias. See

[Common IO Settings](../Common-IO-Settings.md).

## Example — 3-line Gray-coded gear selector

A selector exposes three Gray-coded digital lines, `G2`, `G1`, `G0`.

1. Type **RBC Input**, alias `Gear Position`.

2. Add the **bit inputs** in order `G2` (MSB), `G1`, `G0` (LSB).

3. The input converts the Gray code to a binary value `0`–`7`, one per position,

   with only one line changing between adjacent gears.

## Troubleshooting

- **Decoded number counts the wrong way:** the bit order is reversed for your

  wiring — change the order the inputs are listed in.

- **One position is always wrong / stuck:** check that line's source input on its

  own; a stuck bit usually means a wiring or threshold problem at the source.

- **Values jump by more than one between positions:** the lines are not actually

  Gray-coded (or one is mis-ordered) — verify the encoder's coding.

- **Unexpected code values:** confirm every intended line is in the list and none

  is listed twice.

## Related

- [Digital Input](Digital-Input.md) — the per-line bit sources.

- [Mux Input](Mux-Input.md) — select one of several inputs by an index.

- [Analog Switch Input](Analog-Switch-Input.md) — decode a multi-position switch on

  a single analog pin.