mirror of
https://github.com/RobTillaart/Arduino.git
synced 2024-10-03 18:09:02 -04:00
126 lines
4.0 KiB
Markdown
126 lines
4.0 KiB
Markdown
|
||
|
||
[](https://github.com/marketplace/actions/arduino_ci)
|
||
[](https://github.com/RobTillaart/float16/actions/workflows/arduino-lint.yml)
|
||
[](https://github.com/RobTillaart/float16/actions/workflows/jsoncheck.yml)
|
||
[](https://github.com/RobTillaart/float16/blob/master/LICENSE)
|
||
[](https://github.com/RobTillaart/Complex/releases)
|
||
|
||
|
||
# float16
|
||
|
||
Arduino library to implement float16 data type.
|
||
|
||
|
||
## Description
|
||
|
||
This **experimental** library defines the float16 (2 byte) data type, including conversion
|
||
function to and from float32 type. It is definitely **work in progress**.
|
||
|
||
The library implements the **Printable** interface so one can directly print the
|
||
float16 values in any stream e.g. Serial.
|
||
|
||
The primary usage of the float16 data type is to efficiently store and transport
|
||
a floating point number. As it uses only 2 bytes where float and double have typical
|
||
4 and 8 bytes, gains can be made at the price of range and precision.
|
||
|
||
|
||
## Specifications
|
||
|
||
|
||
| attribute | value | notes |
|
||
|:----------|:-------------|:--------|
|
||
| size | 2 bytes | layout s eeeee mmmmmmmmmm
|
||
| sign | 1 bit |
|
||
| exponent | 5 bit |
|
||
| mantissa | 11 bit | ~ 3 digits
|
||
| minimum | 5.96046 E−8 | smallest positive number.
|
||
| | 1.0009765625 | 1 + 2^−10 = smallest nr larger than 1.
|
||
| maximum | 65504 |
|
||
| | |
|
||
|
||
|
||
## Interface
|
||
|
||
to elaborate
|
||
|
||
#### Constructors
|
||
|
||
- **float16(void)** defaults to zero.
|
||
- **float16(double f)** constructor.
|
||
- **float16(const float16 &f)** copy constructor.
|
||
|
||
|
||
#### Conversion
|
||
|
||
- **double toDouble(void)** convert to double (or float).
|
||
- **uint16_t getBinary()** get the 2 byte binary representation.
|
||
- **void setBinary(uint16_t u)** set the 2 bytes binary representation.
|
||
- **size_t printTo(Print& p) const** Printable interface.
|
||
- **void setDecimals(uint8_t d)** idem, used for printTo.
|
||
- **uint8_t getDecimals()** idem.
|
||
|
||
Note the setDecimals takes one byte per object which is not efficient for arrays of float16.
|
||
See array example for efficient storage using set/getBinary() functions.
|
||
|
||
|
||
#### Compare
|
||
|
||
Standard compare functions. Since 0.1.5 these are quite optimized,
|
||
so it is fast to compare e.g. 2 measurements.
|
||
|
||
- **bool operator == (const float16& f)**
|
||
- **bool operator != (const float16& f)**
|
||
- **bool operator > (const float16& f)**
|
||
- **bool operator >= (const float16& f)**
|
||
- **bool operator < (const float16& f)**
|
||
- **bool operator <= (const float16& f)**
|
||
|
||
|
||
#### Math (basic)
|
||
|
||
Math is done by converting to double, do the math and convert back.
|
||
These operators are added for convenience only.
|
||
Not planned to optimize these.
|
||
|
||
- **float16 operator + (const float16& f)**
|
||
- **float16 operator - (const float16& f)**
|
||
- **float16 operator \* (const float16& f)**
|
||
- **float16 operator / (const float16& f)**
|
||
- **float16& operator += (const float16& f)**
|
||
- **float16& operator -= (const float16& f)**
|
||
- **float16& operator \*= (const float16& f)**
|
||
- **float16& operator /= (const float16& f)**
|
||
|
||
negation operator.
|
||
- **float16 operator - ()** fast negation.
|
||
|
||
- **int sign()** returns 1 == positive, 0 == zero, -1 == negative.
|
||
- **bool isZero()** returns true if zero. slightly faster than **sign()**.
|
||
- **bool isInf()** returns true if value is (-)infinite.
|
||
|
||
|
||
## Notes
|
||
|
||
|
||
## Future
|
||
|
||
|
||
#### 0.1.6
|
||
|
||
- update documentation.
|
||
- unit tests of the above.
|
||
- isNan().
|
||
|
||
|
||
#### later
|
||
|
||
- update documentation.
|
||
- error handling.
|
||
- divide by zero errors.
|
||
- look for optimizations.
|
||
- rewrite **f16tof32()** with bit magic.
|
||
- add storage example - with SD card, FRAM or EEPROM
|
||
- add communication example - serial or Ethernet?
|
||
|