- Generated on Tue Nov 24 2020 19:47:04 by
1.8.17
Generic data structure for expressing physical values. More...
Generic data structure for expressing physical values.
Physical data is expressed in a 3-dimensional tuple of values. In addition to the data fields, this struct contains further the (physical) unit and the scale factor of the data. The unit is expressed as constant. The scale factor is expressed as power of 10 (10^factor).
The combination of signed 16-bit numbers with and the scale factor gives us a very high dynamic range (from -32*10^-131 to 32*10^130). In a wider sense we are saving the values as fixed floating points...
The scale factor is identical for all 3 values.
In a traditional (scientific) computational system the obvious choice for the used data type would be to use floats. We are however on heavily resource constrained (even 8-bit) embedded systems, so we use int16_t here. As most sensor are in some way ADC based, they normally do not use a higher accuracy than 12-14bit, so using 16-bit integers to represent this data is good enough in most cases.
#include <phydat.h>
Data Fields | |
| int16_t | val [PHYDAT_DIM] |
| the 3 generic dimensions of data | |
| uint8_t | unit |
| the (physical) unit of the data | |
| int8_t | scale |
| the scale factor, 10^*scale* | |
1.8.17