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

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(Created page with "*'''Node Home''' *'''All Data Types''' {{DataTypeTableStart|}} |- |<onlyinclude>{{DataType|Temperature}}||16 bit fixed point integer in whic...")
 
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|<onlyinclude>{{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.</onlyinclude>
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|<onlyinclude>{{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.</onlyinclude>
 
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The {{DataType|Temperature}} datatype is returned by the {{Port|gpio|pcbTemp}} portvar (the exact format is configured by setting {{Port|gpio|tempPrecision}}). Generically, the value read from {{Port|gpio|pcbTemp}} is the whole degrees followed by <code>tempPrecision</code> bits of fractional value. The following are examples on how to properly interpret a {{DataType|Temperature}} value:
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The {{DataType|Temperature}} datatype is returned by the {{Port|gpio|pcbTemp}} portvar (the exact format is configured by setting {{Port|gpio|tempPrecision}}). 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:
  
 
By default {{Port|gpio|tempPrecision}} is <code>0</code>:
 
By default {{Port|gpio|tempPrecision}} is <code>0</code>:
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  SIMTempFrac  = (SIMTempFrac << (8 - GPIO.tempPrecision));            // re-adjust the fractional 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)</code>
 
  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)</code>
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'''''Note:''' ''<code>SIMTempWhole</code>'' and ''<code>SIMTempFrac</code>'' only need to be of type ''{{DataType|Byte}}'' to fit the highest possible values''

Revision as of 15:59, 1 February 2013

Data Type Description
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 shipCelsius to true for Celsius, or false for Fahrenheit.

The Temperature datatype is returned by the pcbTemp portvar (the exact format is configured by setting tempPrecision). Generically, the value read from pcbTemp is an 8-bit value in whole degrees followed by a tempPrecision-bit value in 1/256ths of a degree. The following are examples on how to properly interpret a Temperature value:

By default tempPrecision is 0: 

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

For handling any other value of tempPrecision: 

SIMTempWhole = (GPIO.pcbTemp >> GPIO.tempPrecision);                  // once the fractional bits are gone, the value is correct
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

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