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<== Date ==> <== Thread ==>
Subject: Re: using stream -calcout
From: Ralph Lange <[email protected]>
To: EPICS Tech Talk <[email protected]>
Date: Fri, 16 Feb 2018 13:30:58 +0100
Hello Li Xing,

Your statements and your protocol file are not consistent.

For the output, your statement seems to say that you send 8 bytes, and your 'out' string in the protocol is indeed sending 8 bytes.
For the returned data, your statement seems to say that you expect 7 bytes, however, the 'in' part of your protocol is trying to receive 14 bytes (characters).

Following your statement (receive 7 bytes), please try using a single record (longin or ai record, depending on desired conversion into a double; no calc needed) and an 'in' part that reads "raw" bytes. Do something like

    out "\xFE\x04\x00\x00\x00\x01\x25\xC5";
    in "%*3r%02r%*2r"

(ignore 3 bytes, read 2 unsigned bytes as big endian, ignore 2 bytes)

If parts of the returned message are fixed, include them in your in format.
E.g., if the return always starts with "FE 04", your in format could be "\xFE\x04%*1r%02r%*2r". This increases robustness, because if the communication gets out of sync, the protocol will not blindly decode bytes at the wrong position.

Cheers,
~Ralph


On Fri, Feb 16, 2018 at 11:27 AM, l123173 <[email protected]> wrote:
Hi all,
     I have a simple question about stream. 
     The device was connected with LAN. If sending " fe 04 00 00 00 01 25 c5 " in Hex,  getting  " fe 04 02 04 08 ae 22 " in Hex. 
     Among the getting bytes（ " fe 04 02 04 08 ae 22 "）, 04 08 was I wanted. Convert  0408(HEX) to decimal was 1032 (4*16**2 +8=1032), and 1032 was the finall result I wanted.
     
    In my programe, I have successfully sent and got the bytes. But I could not get the 1032, I want to achieve it using scalcout, but failed.
    Could you please give me some suggestion.

my proto file:
-------------------------------------------------------
get_high {
   out "\xFE\x04\x00\x00\x00\x01\x25\xC5";
   in "%*c%*c%*c%*c%*c%*c%c%c%*c%*c%*c%*c%*c%*c"; 
#   in "%s";
}

get_low {
   in "%*c%*c%*c%*c%*c%*c%*c%*c%c%c%*c%*c%*c%*c";
}
References:
using stream -calcout l123173
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