GY-63_MS5611/libraries/ADS1x15/README.md

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# ADS1X15

Arduino library for I2C ADC ADS1015, ADS1115,

## Description

This library should work for the devices mentioned below,
although not all sensors support all functionality.

| Device | Channels | Resolution | Max sps | Comparator | ProgGainAMP | Notes |
|:----:|:----:|:----:|:----:|:----:|:----:|:----|
| ADS1013 | 1 | 12 | 3300 | N  | N |        |
| ADS1014 | 1 | 12 | 3300 | Y  | Y |        |
| ADS1015 | 4 | 12 | 3300 | Y  | Y |        |
| ADS1113 | 1 | 16 | 860  | N  | N |        |
| ADS1114 | 1 | 16 | 860  | Y  | Y |        |
| ADS1115 | 4 | 16 | 860  | Y  | Y | Tested |

As the 1015 and the 1115 are both 4 channels these are the most
interesting from functionality point of view as these can also do
differential measurement.

#### Note

This readme file is work in progress.


## Interface

The address of the ADS1113/4/5 is determined by to which pin the ADDR
is connected to:

| ADDR pin connected to | Address | Note |
|:----:|:----:|:----:|
| GND | 0x48 | default |
| VDD | 0x49 | |
| SDA | 0x4A | |
| SCL | 0x4B | |

- **ADS1x15()** constructor, should not be used.
- **ADS1013(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.
- **ADS1014(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.
- **ADS1015(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.
- **ADS1113(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.
- **ADS1114(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.
- **ADS1115(address, TwoWire \*wire = &Wire)** Constructor with device address, 
and optional the Wire interface as parameter.

The function **setWireClock(uint32_t speed)** is used to set the clockspeed of the used 
I2C interface. 

The function **getWireClock()** is a prototype. It returns the value set by setWireClock().
This is not perse the actual value. When no value is set **getWireClock()** returns 0.
Need to implement a read / calculate from low level I2C code (e.g. TWBR on AVR).

After construction the **ADS.begin()** need to be called. This will return false 
if an invalid address is used.
The function **isConnected()** can be used to verify the reading of the ADS.
The function **reset()** is sets the parameters to their initial value as 
in the constructor.


#### Programmable Gain

- **setGain(gain)** set the gain value, indicating the maxVoltage that can be measured
Adjusting the gain allows one to make more precise measurements.
See table below.
- **getGain()** returns the gain value (index).

| PGA value | Max Voltage | note |
|:----:|:----:|:----:|
| 0  | ±6.144V | default |
| 1  | ±4.096V |         |
| 2  | ±2.048V |         |
| 4  | ±1.024V |         |
| 8  | ±0.512V |         |
| 16 | ±0.256V |         |

- **getMaxVoltage()** returns the max voltage with the current gain.
- **toVoltage(raw = 1)** converts a raw measurement to a voltage.
Can be used for normal and differential measurements.
The default value of 1 returns the conversion factor for any raw number.

The voltage factor can also be used to set HIGH and LOW threshold registers 
with a voltage in the comparator mode.
Check the examples.

```cpp
  float f = ADS.toVoltage();
  ADS.setComparatorThresholdLow( 3.0 / f );
  ADS.setComparatorThresholdLow( 4.3 / f );
```

#### Operational mode

The ADS sensor can operate in single shot or continuous mode. 
Depending on how often one needs a conversion one can tune the mode.
- **setMode(mode)** 0 = CONTINUOUS, 1 = SINGLE (default)
- **getMode()** returns current mode 0 or 1, or ADS1X15_INVALID_MODE = 0xFE.


#### Datarate

- **setDataRate(dataRate)** Datarate depends on type of device.
For all devices the index 0..7 can be used, see table below.
Values above 7 ==> will be set to the default 4.
- **getDataRate()** returns the current datarate (index).

The library has no means to convert this index to the actual numbers
as that would take 32 bytes. 

Datarate in samples per second, based on datasheet numbers.

| datarate | ADS101x | ADS 111x | Notes & remarks |
|:----:|----:|----:|:----:|
| 0 | 128  | 8   | slowest |
| 1 | 250  | 16  |  |
| 2 | 490  | 32  |  |
| 3 | 920  | 64  |  |
| 4 | 1600 | 128 | default |
| 5 | 2400 | 250 |  |
| 6 | 3300 | 475 |  |
| 7 | 3300 | 860 | fastest |


#### ReadADC Single mode

Reading the ADC is very straightforward, the **readADC()** function handles
all in one call. Under the hood it uses the asynchronuous calls.
- **int16_t readADC(pin)** normal ADC functionality, pin = 0..3. 
If the pinnumber is out of range, this function will return 0.

To read the ADC in an asynchronuous way (e.g. to minimize blocking) one has to use three calls:
- **requestADC(pin)**  Start the conversion. pin = 0..3. 
- **isBusy()**         Is the conversion not ready?
- **isReady()**        Is the conversion ready? (= wrapper around **isBusy()** )
- **getValue()**       Read the result of the conversion.


in terms of code
```cpp

  void setup()
  {
    // other setup things here
    ADS.requestADC(pin);
  }


  void loop()
  {
    if (ADS.isReady())
    {
      val = ADS.getValue();
      ADS.requestADC(pin);       // request new conversion
    }
    // do other things here
  }

```
See examples

## ReadADC Differential

For reading the ADC in a differential way there are 4 calls possible.
- **readADC_Differential_0_1()** returns the difference between 2 ADC pins.
- **readADC_Differential_0_3()** ADS1x15 only
- **readADC_Differential_1_3()** ADS1x15 only
- **readADC_Differential_2_3()** ADS1x15 only
- **readADC_Differential_0_2()** ADS1x15 only - in software (no async equivalent)
- **readADC_Differential_1_2()** ADS1x15 only - in software (no async equivalent)

The differential reading of the ADC can also be done with asynchronuous calls.
- **requestADC_Differential_0_1()** starts conversion for differential reading
- **requestADC_Differential_0_3()** ADS1x15 only
- **requestADC_Differential_1_3()** ADS1x15 only
- **requestADC_Differential_2_3()** ADS1x15 only

After one of these calls one need to call
- **isBusy()**  Is the conversion ready?
- **getValue()** Read the result of the conversion.


#### ReadADC continuous mode

To use the continuous mode one need three calls
- **setMode(0)** 0 = CONTINUOUS, 1 = SINGLE (default)
- **readADC()** or **requestADC()** to get the continuous mode started.
- **getValue()** to return the last value read by the device.
Calling this over and over again can give the same value multiple times.

By using **isBusy()** or **isReady()** one can wait until new data is available.
Or one can use the **ALERT/RDY** pin to trigger via hardware the readyness of the conversion.

See examples.


#### Threshold registers ==> mode RDY pin

If the thresholdHigh is set to 0x0100 and the thresholdLow to 0x0000
the **ALERT/RDY** pin is triggered when a conversion is ready.
- **setComparatorThresholdLow(0x0000)**
- **setComparatorThresholdHigh(0x0100)**

See examples.


## Comparator

Please read Page 15 of the datasheet as the behavior of the
comparator is not trivial.


#### Comparator Mode

When configured as a **TRADITIONAL** comparator, the **ALERT/RDY** pin asserts
(active low by default) when conversion data exceed the limit set in the
high threshold register. The comparator then deasserts when the input
signal falls below the low threshold register value.

If the comparator **LATCH** is set, the **ALERT/RDY** pin asserts and it will be
reset after reading the sensor (conversion register) again.
*An SMB alert command (00011001) on the I2C bus will also reset the alert state.*
*Not implemented in the library (yet)*

In **WINDOW** comparator mode, the **ALERT/RDY** pin asserts if conversion data exceeds
the high threshold register or falls below the low threshold register.
In this mode the alert is held if the **LATCH** is set. This is similar as above.


#### Polarity

Default state of the **ALERT/RDY** pin is **LOW**, can be to set **HIGH**.


#### Latch

Holds the **ALERT/RDY** to **HIGH** (or **LOW** depending on polarity) after triggered
even if actual value has been 'restored to normal' value.


#### QueConvert

Set the number of conversions before trigger activates.
The **setComparatorQueConvert(uint8_t mode)** is used to set the number of
conversions that exceed the threshold before the **ALERT/RDY** pin is set **HIGH**.
A value of 3 (or above) effectively disables the comparator. See table below.

| value | meaning | notes |
|:----:|:----|:----|
| 0 | trigger alert after 1 conversion  | |
| 1 | trigger alert after 2 conversions | |
| 2 | trigegr alert after 4 conversions | |
| 3 | Disable comparator | default |


#### Threshold registers comparator mode

Depending on the comparator mode **TRADITIONAL** or **WINDOW** the thresholds registers
mean something different see - Comparator Mode above or datasheet.
- **setComparatorThresholdLow(lo)** set the low threshold; take care the hi >= lo
- **setComparatorThresholdHigh(hi)** set the high threshold; take care the hi >= lo
- **getComparatorThresholdLow()** returns set value
- **getComparatorThresholdHigh()** returns set value


## Future ideas & improvements

- Improve documentation
- more examples?
- SMB alert command (00011001) on I2C bus?
- implement missing Differential reads in software.
- testing....


## Operation

See examples