HC4067

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Arduino library for CD74HC4067 1 x 16 channel multiplexer and compatibles.

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# HC4067

HC4067 is an Arduino library for a HC4067 1 x 16 channel multiplexer.

## Description

HC4067 is a library to control the CD74HC4067 16 channel
multiplexer / demultiplexer and compatible devices.

The HC4067 allows e.g one analog port read up to 16 different analog channels,
or one digital port to read the state of 16 buttons.

It is also possible to use the HC4067 to select an OUTPUT channel.
The signal pin can be connected to VCC (5V) or an IO pin set to OUTPUT.
Only the selected channel can show the HIGH level of the IO pin if set to HIGH.
Not selected pins will all be set to LOW.

The channel selection is done with four select lines **S0..S3**.

The device can be enabled/disabled by the enable line **E**.

### 0.3.0 breaking change

Version 0.3.0 has a bugfix for **setChannel()** which obsolete all previous versions.

### Compatibles

Not tested, considered compatible.
- CD74HC4067, 74HC4067, 74HCT4067

### Related

- https://github.com/RobTillaart/HC4051  (1x8 mux)
- https://github.com/RobTillaart/HC4052  (2x4 mux)
- https://github.com/RobTillaart/HC4053  (3x2 mux)
- https://github.com/RobTillaart/HC4067  (1x16 mux)
- https://github.com/RobTillaart/MAX14661 (2x16 mux, I2C)
- https://github.com/RobTillaart/I2C_HC4067  (1x16 mux - using I2C PCF8574)
- https://tronixstuff.com/2013/08/05/part-review-74hc4067-16-channel-analog-multiplexerdemultiplexer/

## Hardware connection

Typical connection is to connect the four **select pins** to four IO pins of your board.

The optional **enablePin E** must be connected to **GND** if not used.
This way the device will be continuous enabled.

Example multiplexing analog in.

```
        processor                      HC4067
     +-------------+              +-------------+
     |             |              |             |
     |          S0 |------------->| S0       Y0 |
     |          S1 |------------->| S1       Y1 |
     |          S2 |------------->| S2       Y2 |
     |          S3 |------------->| S3       Y3 |
     |             |              |          Y4 |
     |          E  |------------->| Enable   Y5 |
     |             |              |          Y6 |
     |             |              |          Y7 |
     |         A0  |<-------------| Z        Y8 |
     |             |              |          Y9 |
     |             |              |         Y10 |
     |             |              |         Y11 |
     |             |              |         Y12 |
     |             |              |         Y13 |
     |        GND  |--------------| GND     Y14 |
     |             |              | VCC     Y15 |
     |             |              |             |
     +-------------+              +-------------+
```

Note: one could add a LED (+resistor) to the Enable line to have visual feedback.

### Less Select lines

Note: the library does not meant for this mode, although it should work.
The GND-ed pins should be set to 255 (not tested).

It is possible to use less IO pins to connect to the S0..S3.
The ones not connected to an IO pin must be connected to GND (preferred).

|  S0   |  S1   |  S2   |  S3   |  pins  |  notes  |
|:-----:|:-----:|:-----:|:-----:|:------:|:-------:|
|  IO   |  IO   |  IO   |  IO   |  0-15  |  default usage
|  IO   |  IO   |  IO   |  GND  |   0-7  |
|  IO   |  IO   |  GND  |  GND  |   0-3  |
|  IO   |  GND  |  GND  |  GND  |   0-1  |

Of course it is possible to set a Select pin to VCC instead of GND.
This will result in another subset of the Y pins to select from.

## Interface

```cpp
#include "HC4067.h"
```

### Constructor

- **HC4067(uint8_t s0, uint8_t s1, uint8_t s2, uint8_t s3, uint8_t enablePin = 255)** constructor.
Set the 4 select pins and optional the enable pin.
If the enablePin == 255 it is considered not used.

### Channels

- **bool setChannel(uint8_t channel, bool disable = true)** set the current channel.
Valid values 0..15, this value is checked (since 0.2.1).
Returns false if channel out of range.  
If the channel is already selected it does not change it.
Note the four channels will not change at the very same moment, 
possibly resulting in an invalid selection for a (very short) time.  
The disable flag can be set to false so the device is not disabled during channel switching.
Default the device is disabled during channel switching to prevent (very short) ghost channels.
Note that a call to **setChannel()** will always enable the device again.
Note the device cannot be disabled if there is no enable pin configured.
- **uint8_t getChannel()** returns the current channel 0..15.
The selected channel is also returned when the multiplexer is disabled.

### Enable

These functions work only if enablePin is set in the constructor.

- **void enable()** enables the device to multiplex.
- **void disable()** disables the device, no channel is selected.
- **bool isEnabled()** returns the current status of the device.
Also returns true if the enablePin is not set in the constructor.

## Future

#### Must

- documentation

#### Should

- test performance **setChannel()** on ESP32 / fast board.
  - should optimized version be AVR only?

#### Could

- mask with valid channels? so subset of 16 can be used
  - if (channel > 15) return false;
  - allow(n), protect(n) to manage the set of allowed pins.

#### Won't (unless requested)

- move code to .cpp file
- uint8_t channelCount() { return 16; };
- cache enable status
- inline the enable/disable
- next() and prev() as channel selector
  - what to do with range borders? ==> stop or wrap? (depends on project)
  - what to do with disable flag? (depends on project)

## Support

If you appreciate my libraries, you can support the development and maintenance.
Improve the quality of the libraries by providing issues and Pull Requests, or
donate through PayPal or GitHub sponsors.

Thank you,

HC4067

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