Experimental Physics and
Industrial Control System

We have some device controlled via raw serial communication. Streamdevice reads a weird 1 byte null data (as far as we are understanding). 

We expect that 15 byte data are read back normally when 7 byte command is sent.

send cmd: 0x16 0x16 0x80 0x00 0x00 0x80 0x1A

read-back: 0x16 0x16 0x80 0x00 0x08 (two 4 byte float) checksum 0x1A

However, unexpected 1 byte  null(\x00) character is read. Sometimes, this null character is read together with our read-back data, which causes an input error as shown in iocshell console message.

Do you have any idea about this?

Thanks,

Hyung JIn Kim

=================================================================

iocshell console message:

2023/09/15 10:57:29.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:29.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:29.912 192.168.85.191:4001 read 1

00
2023/09/15 10:57:31.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:31.895 192.168.85.191:4001 read 1

00
2023/09/15 10:57:31.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:31.912 192.168.85.191:4001 read 1

00
2023/09/15 10:57:32.913154 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: Input "<00><16><16><80><00><08><00><80>"C<00><00><c0>@m<1a><00>"
2023/09/15 10:57:32.913470 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: mismatch after 0 bytes ""
2023/09/15 10:57:32.913730 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: got "<00><16><16><80><00><08><00><80>"C..." where "<16>" was expected
2023/09/15 10:57:33.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:33.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:33.912 192.168.85.191:4001 read 1

00
2023/09/15 10:57:35.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:35.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:35.912 192.168.85.191:4001 read 1

00
2023/09/15 10:57:37.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:37.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:37.911 192.168.85.191:4001 read 1

00
2023/09/15 10:57:39.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:39.895 192.168.85.191:4001 read 1

00
2023/09/15 10:57:39.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:40.904437 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: Input "<00><16><16><80><00><08><00><80>"C<00><00><c0>@m<1a>"
2023/09/15 10:57:40.904748 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: mismatch after 0 bytes ""
2023/09/15 10:57:40.905012 PHWRB41 SCL32-RF03:SSPA-B41:#getInfo: got "<00><16><16><80><00><08><00><80>"C..." where "<16>" was expected
2023/09/15 10:57:41.891 192.168.85.191:4001 write 7

16 16 80 00 00 80 1a
2023/09/15 10:57:41.903 192.168.85.191:4001 read 15

16 16 80 00 08 00 80 22 43 00 00 c0 40 6d 1a
2023/09/15 10:57:41.911 192.168.85.191:4001 read 1

00

...

===========================================================================

For reference, here is a part of our protocol:

Terminator  = "\x1A";
ExtraInput    = Ignore;
query_head    = "\x16\x16\x80";
query_tail    = "\x00%2<sum8>";

get_dev_info
{
    Separator = "";
    out  $query_head "\x00" $query_tail;
    in  $query_head "\x00\x08"
        "%#4R"
        "%2<sum8>";
}

Our database is as follows:

record(aai, "${SYS}${SUBSYS}${DEV}${SUBDEV}#getInfo") {
  field (DESC, "Get Freq and Firmware")
  field (SCAN, "2 second")
  field (DTYP, "stream")
  field (INP,  "@sspaRFPT.proto get_dev_info(${SYS}${SUBSYS}${DEV}${SUBDEV}) $(PORT)")
  field (NELM, "2")
  field (FTVL, "FLOAT")
}

===========================================================================

Our st.cmd looks like :

...

drvAsynIPPortConfigure("PHWRB41", "192.168.85.191:4001", 0,0,0)
asynSetOption("PQWR001", 0, "baud", "115200")
#asynSetOption("PQWR001", 0, "bits", "8")
#asynSetOption("PQWR001", 0, "stop", "1")
#asynSetOption("PQWR001", 0, "parity", "none")

...

asynSetTraceMask  ("PHWRB41", 0, 9)
asynSetTraceIOMask("PHWRB41", 0, 4)
dbLoadTemplate("${TOP}/db/sspaRFPT.substitutions", "")

...