StreamDevice: ai Records

Normal Operation

Depending on the format type, different record fields are used for output and input. The variable x stands for the written or read value.

DOUBLE format (e.g. %f):

Output: x=(VAL-AOFF)/ASLO
Input: VAL=(x*ASLO+AOFF)*(1.0-SMOO)+VAL*SMOO
In both cases, if ASLO==0.0, it is treated as 1.0. Default values are ASLO=1.0, AOFF=0.0, SMOO=0.0.
If input is successful, UDF is cleared.

LONG format (e.g. %i):

Output: x=RVAL
Input: RVAL=x
Note that the record calculates VAL=(((RVAL+ROFF)*ASLO+AOFF)*ESLO+EOFF)*(1.0-SMOO)+VAL*SMOO if LINR=="LINEAR". ESLO and EOFF might be set in the record definition. StreamDevice does not set it. For example, EOFF=-10 and ESLO=0.000305180437934 (=20.0/0xFFFF) maps 0x0000 to -10.0, 0x7FFF to 0.0 and 0xFFFF to 10.0. Using unsigned formats with values ≥ 0x800000 gives different results on 64 bit machines.

ENUM format (e.g. %{):

Not allowed.

STRING format (e.g. %s):

Not allowed.

Initialization

During initialization, the @init handler is executed, if present. In contrast to normal operation, in DOUBLE input SMOO is ignored (treated as 0.0).

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Dirk Zimoch, 2005