Re: bit shifting operators

[Florian Feldbauer <florian@ep1.ruhr-uni-bochum.de>]

Hey,

you could use a CALC record to get the individual fields of the 16-bit value.
I'm using a similar ADC where bit 15 is an ALERT-flag, bits 14-12 code the channel,
and bits 11-0 hold the conversion result.
For accessing these three values I'm using:

record( longin, "AD7998:$(ID):CONVERSION:RESULT__" ) {
  field( DTYP, "stream" )
  field( INP,  "@ad7998.proto rConv($(ID)) I2C" )
  field( FLNK, "AD7998:$(ID):CONVERSION:RESULT:SPLIT__" )
}

record( calc, "AD7998:$(ID):CONVERSION:RESULT:SPLIT__" ) {
  field( INPA, "AD7998:$(ID):CONVERSION:RESULT__ NPP NMS" )
  field( CALC, "b := (( A & 32768 ) >> 15 ); c := (( A & 28672 ) >> 12 ); ( A & 4095 )" )
  field( FLNK, "AD7998:$(ID):CONVERSION:FANOUT__" )
}

Field B of the CALC records contains the alert flag, field C the channel number
and VAL the actual conversion result.

Hope that helps.
Cheers,
Florian

On 06/28/2016 11:30 AM, info22@online.de wrote:

Hello,

I am trying to read the voltag from an 8-channel adc via I2C.

 

My result is a 16 bit value (for example 0010 0000 0010 0000). The bits15-12 "0010" respresent the channel (Ch1=0, CH2=1, CH3=2 ....). 

 

I can get the channel value with a SHFT-field:

record( longin, "ADC:RESULT" ) {
  field( DTYP, "stream" )
  field( INP,  "@adc.proto readReg($(ID)) I2C" )
}

record( mbbiDirect, "ADC:RESULT:CHANNEL" ) {
  field( DTYP, "Raw Soft Channel" )
  field( INP,  "ADC:RESULT.VAL")
  field(SHFT, "12")

}

 

Now I want to get the first bits 0-12 and convert the value to voltage-value. To convert this value I use the "ASLO"-field.

But I don't know which is the best way to get the value of the first 12 bits.

 

Thanks,

Raul

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| Dr. Florian Feldbauer                |
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