Difference between revisions of "SHIP:Data Types:Temperature"

From Serious Documentation
Jump to: navigation, search
Line 3: Line 3:
  
 
<onlyinclude>
 
<onlyinclude>
−
The {{DataType|Temperature}} datatype is returned by the {{Port|gpio|pcbTemp}} portvar (the exact format is configured by setting {{Port|gpio|tempPrecision}}).
+
The {{DataType|Temperature}} datatype is returned by the {{Portvar|gpio|pcbTemp}} portvar with a variable format configured by setting {{Portvar|gpio|tempPrecision}}.
 
{{DataTypeTableStart|}}
 
{{DataTypeTableStart|}}
 
|-
 
|-
−
|{{DataType|Temperature}}||16 bit fixed-point-integer in which the upper portion is in whole degrees and the lower portion is in 256ths of a degree. Set {{SysVar|shipCelsius}} to {{Reserved|true}} for Celsius, or {{Reserved|false}} for Fahrenheit.
+
|{{DataType|Temperature}}||16 bit fixed-point-integer interpreted as an 8-bit value in whole degrees followed by a {{Portvar|gpio|tempPrecision}}-bit value in 1/256ths of a degree. Set {{SysVar|shipCelsius}} to {{Reserved|true}} for Celsius, or {{Reserved|false}} for Fahrenheit.
 
|}</onlyinclude>
 
|}</onlyinclude>
  
−
Generically, the value read from {{Port|gpio|pcbTemp}} is an 8-bit value in whole degrees followed by a <code>tempPrecision</code>-bit value in 1/256ths of a degree. The following are examples on how to properly interpret a {{DataType|Temperature}} value:
+
The following are examples on how to properly interpret a {{DataType|Temperature}} value:
  
−
By default {{Port|gpio|tempPrecision}} is <code>0</code>:
+
If {{Portvar|gpio|tempPrecision}} is <code>0</code> (default):
 
  <code>SIMTempWhole = GPIO.pcbTemp;  // the value is good as-is
 
  <code>SIMTempWhole = GPIO.pcbTemp;  // the value is good as-is
 
  SIMTempFrac  = 0;            // unnecessary</code>
 
  SIMTempFrac  = 0;            // unnecessary</code>
  
−
For handling any other value of {{Port|gpio|tempPrecision}}:
+
Otherwise (if your GUI does not change {{Portvar|gpio|tempPrecision}}, replace with constant values):
−
  <code>SIMTempWhole = (GPIO.pcbTemp >> GPIO.tempPrecision);                  // once the fractional bits are gone, the value is correct
+
  <code>SIMTempWhole = (GPIO.pcbTemp >> GPIO.tempPrecision);                  // get rid of the fractional bits
 
  SIMTempFrac  = (GPIO.pcbTemp & (0x00FF >> (8 - GPIO.tempPrecision))); // get rid of the degree bits
 
  SIMTempFrac  = (GPIO.pcbTemp & (0x00FF >> (8 - GPIO.tempPrecision))); // get rid of the degree bits
 
  SIMTempFrac  = (SIMTempFrac << (8 - GPIO.tempPrecision));            // re-adjust the fractional bits
 
  SIMTempFrac  = (SIMTempFrac << (8 - GPIO.tempPrecision));            // re-adjust the fractional bits

Revision as of 16:21, 1 February 2013


The Temperature datatype is returned by the pcbTemp portvar with a variable format configured by setting tempPrecision.

Data Type Description
Temperature 16 bit fixed-point-integer interpreted as an 8-bit value in whole degrees followed by a tempPrecision-bit value in 1/256ths of a degree. Set shipCelsius to true for Celsius, or false for Fahrenheit.

The following are examples on how to properly interpret a Temperature value:

If tempPrecision is 0 (default): 

SIMTempWhole = GPIO.pcbTemp;  // the value is good as-is
SIMTempFrac  = 0;             // unnecessary

Otherwise (if your GUI does not change tempPrecision, replace with constant values): 

SIMTempWhole = (GPIO.pcbTemp >> GPIO.tempPrecision);                  // get rid of the fractional bits
SIMTempFrac  = (GPIO.pcbTemp & (0x00FF >> (8 - GPIO.tempPrecision))); // get rid of the degree bits
SIMTempFrac  = (SIMTempFrac << (8 - GPIO.tempPrecision));             // re-adjust the fractional bits
SIMTempFrac  = (SIMTempFrac*100)/256;                                 // fix up the value to be a proper fraction (currently it is from 0/256 to 255/256 of a degree)

Note: SIMTempWhole and SIMTempFrac only need to be of type Byte to fit the highest possible values

Retrieved from "https://techref.myserious.com/index.php?title=SHIP:Data_Types:Temperature&oldid=2670"