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# AD520X

Arduino library for SPI AD5204 and AD5206 digital potentiometers.

Works with the AD840x series too (see PR #15)


## Description

The library is experimental as not all functionality is tested (enough).

The **AD5204** (4 channels) and **AD5206** (6 channels) are SPI based digital potentiometers.
This library consists of a base class **AD520X** that does the work.

The interface is straightforward, one can set a value per channels between 0..255.

|  type    |  channels  |  1 kΩ | 10 kΩ | 50 kΩ | 100 kΩ |  works    |
|:---------|:----------:|:-----:|:-----:|:-----:|:------:|:----------|
|  AD5204  |    4       |       |   V   |   V   |   V    | confirmed |
|  AD5206  |    6       |       |   V   |   V   |   V    | confirmed |
|  AD8400  |    1       |   V   |   V   |   V   |   V    | confirmed |
|  AD8402  |    2       |   V   |   V   |   V   |   V    |
|  AD8403  |    4       |   V   |   V   |   V   |   V    | confirmed |  see PR #15

The library is not yet confirmed to work for **AD8402** (2 channels).
This device has  a very similar interface (datasheet comparison) so it should work. If you can confirm the AD8402 works, please let me know.


## Interface


### Constructors

- **AD520X(uint8_t select, uint8_t reset, uint8_t shutdown, uint8_t dataOut = 255, uint8_t clock = 255)** constructor  
Base class, not to be used directly.
If dataOut and clock are set to 255 (default) it uses hardware SPI. 
If dataOut and clock are set to another (valid) value) it uses software SPI.
reset and shutdown may be set to 255 too, which effectively disables them.  
- **AD5204(select, reset, shutdown, dataOut = 255, clock = 255)** has 4 channels.
- **AD5206(select, reset, shutdown, dataOut = 255, clock = 255)** has 6 channels.
- **AD8400(select, reset, shutdown, dataOut = 255, clock = 255)** has 1 channel.
- **AD8402(select, reset, shutdown, dataOut = 255, clock = 255)** has 2 channels.
- **AD8403(select, reset, shutdown, dataOut = 255, clock = 255)** has 4 channels.

Note: hardware SPI is 10+ times faster on an UNO than software SPI. 


### Base

Since 0.2.0 the functions have more default parameters. Potentiometer is default pot 0 
and value is default the **AD520X_MIDDLE_VALUE** of 128.

- **void begin(uint8_t value = 128)** value is the initial value of all potentiometer.
- **void reset(uint8_t value = 128)** resets the device and sets all potentiometers to value, default 128.

#### Value

- **bool setValue(uint8_t pm = 0, uint8_t value = 128)** set a potentiometer to a value. 
Default value is middle value.  
Returns true if successful, false if not.
- **bool setValue(uint8_t pmA, uint8_t pmB, uint8_t value)** set two potentiometers to same value.
Note, no default value!
Returns true if successful, false if not.
- **void setAll(uint8_t value = 128)** set all potentiometers to the same value e.g. 0 or max or mid value.
Can typically be used for **mute**.
- **uint8_t getValue(uint8_t pm = 0)** returns the last set value of a specific potentiometer.


#### percentage

- **bool setPercentage(uint8_t pm = 0, float percentage = 50)** similar to setValue, percentage from 0..100%  
Returns true when successful, false if not.
- **bool setPercentage(uint8_t pmA, uint8_t pmB, float percentage)** similar to setValue, percentage from 0..100%.
Note, no default value.
Returns true when successful, false if not.
- **float getPercentage(uint8_t pm = 0)** return the value of potentiometer pm as percentage.


The library has defined **#define AD520X_MIDDLE_VALUE  128**


### Hardware SPI

To be used only if one needs a specific speed for hardware SPI.  
Has no effect on software SPI.

- **void setSPIspeed(uint32_t speed)** set SPI transfer rate.
- **uint32_t getSPIspeed()** returns SPI transfer rate.


### ESP32 specific

This functionality is new in 0.1.2 and it is expected that the interface will change
in the future. 

- **void selectHSPI()** in case hardware SPI, the ESP32 has two options HSPI and VSPI.
- **void selectVSPI()** see above.
- **bool usesHSPI()** returns true if HSPI is used.
- **bool usesVSPI()** returns true if VSPI is used.

The **selectVSPI()** or the **selectHSPI()** needs to be called BEFORE the **begin()** function.


### Misc

- **uint8_t pmCount()** returns the number of internal potentiometers.
- **void powerOn()** switches the module on.
- **void powerOff()** switches the module off.
- **bool isPowerOn()** returns true if on (default) or false if off.


### Obsolete

- **void powerDown()** OBSOLETE since 0.3.0 => use powerOff() instead.


## Operations

See examples.


## Future


#### 0.3.1

- **setGroupValue(mask, value)** bit mask to set 0..8 channels in one call
  - loop over mask ?
- **setGroupPercentage(mask, value)** bit mask to set 0..8 channels in one call
  - wrapper
- move all code to .cpp file


#### Must


#### Should

- **void setInvert(uint8_t pm)** invert flag per potentiometer.
   - 0..255 -> 255..0
   - 1 uint8_t can hold 8 flags
   - will slow performance.
   - how does this work with **stereo** functions.
   - at what level should invert work.
- **bool getInvert(uint8_t pm)**


#### Could (only if requested.)

- **AD520X_MIDDLE_VALUE** 127 ?   (0.4.0?)
- **setSWSPIdelay()** to tune software SPI?
  - bit delay / not byte delay
  - unit microseconds
  

#### Wont

- **void setGamma(uint8_t pm, float gamma)**
  - logarithmic effect? easier with setPercentage()
  - see gamma library.
- **void follow(pm_B, pm_A, float percentage = 100)**
  - makes pm_B follow pm_A unless pm_B is addressed explicitly
  - e.g. to be used for **stereo** channels.
  - array cascade = 0xFF or pm_A.
  - It will follow pm_A for certain percentage default 100.