Re: Passing a raw byte value from st.cmd to a StreamDevice proto file

[Andrew Johnson <anj@aps.anl.gov>]

Hi Michael,

On 07/29/2015 07:52 AM, Michael Ritzert wrote:
> I'm looking for a way to pass a raw byte parameter from st.cmd through the
> database to the format string in a StreamDevice proto file. I investigated both
> passing a binary value through dbLoadRecords, but the obvious options \x24 or
> \044 (e.g. dbLoadRecords("gf100.db","PORT=L0,ADDR=0,MAC=\x24")) do not work as
> I had hoped (the \ is swallowed, the rest is taken verbose). I also tried to
> have the string interpreted as a number in the proto file by putting it into a
> formatting statement as if \$1 was another record name. All this got me was
> error messages.
> 
> Does anybody have a suggestion?

Have you tried doubling-up on the back-slash character in your macro
string? The IOC does translate escaped characters into their raw form
when loading field value strings from a .db file, but that translation
only takes place at the last stage of interpretation. Your macro string
goes through more than one level of unescaping between the st.cmd file
and the record field itself, so I think you should try using 2 or more
back-slash characters instead of just one, e.g.
	dbLoadRecords("gf100.db","PORT=L0,ADDR=0,MAC=\\x24")
or
	dbLoadRecords("gf100.db","PORT=L0,ADDR=0,MAC=\\\x24")

EPICS understands these standard C escapes:
	\a \b \f \n \r \t \v \\ \? \' \"
	\ooo where o is an octal digit
	\xHH where H is a hex digit

HTH,

- Andrew

-- 
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