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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**.


#### 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://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 |
     |             |              |             |
     +-------------+              +-------------+
```


#### 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"
```

#### Core

- **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.
- **void setChannel(uint8_t channel)** set the current channel.
Valid values 0..15, this value is not checked, only the lower 4 bits will be used.
- **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 HC4067 to multiplex.
- **void disable()** disables the HC4067, no channel is selected.
- **bool isEnabled()** returns the current status of the HC4067.
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

- next() and prev() as channel selector.
  - what to do with range borders? ==> stop?

#### Won't (unless requested)

- check channel in setChannel() ?
  - return true if in range, false otherwise.
- move code to .cpp file


## 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,