Experimental Physics and
Industrial Control System

Florian Feldbauer <[email protected]> · Wed, 15 Mar 2017 10:53:05 +0100

Dear all,

sorry for reviving this old thread, but I received several questions if

and how I solved this problem during the last weeks.

Since it was never answered in Tech-Talk and the solution cannot be

found in the stream device documentation, I wanted to share it here:

To get the checksum as ASCII string one can use the "+" flag. So the

protocol for the example below would look like:

getActRotspd {
  # get actual frequency for pump
  # Example of command:
  # field (INP, "@Pfeiffer_TCP350.proto getActRotspd($(ADD)) $(PORT)")

  out "\${1}0030902=?%+<sum8>";
  in  "\${1}1030906%06u%+<sum8>";
}

Best regards,

Florian

On 11/21/2013 11:04 AM, Florian Feldbauer wrote:

Hey Dirk,

we want to control some turbo drag pumps from Pfeiffer Vacuum with EPICS.

The pumps have a RS485 interface, so we can use StreamDevice and asyn

for the

communication.
The protocol from Pfeiffer looks like this (using ASCII symbols):
3 digit address
2 digit action (read "00" or write "10")
3 digit parameter number
2 digit data length
x digits data (according to data length)
3 digit checksum
CR

The checksum is the sum of all ASCII symbols up to preceding checksum

modulo 256 (decimal)

converted into ASCII string.

As an example, reading the actual rotation speed for address 123 would

be:

"1230030902=?112\r"

Would it be possible to add a corresponding pseudo-converter to

StreamDevice with little effort,

or would it be easier to use records for the calculation?
In principal we need something like %<sum8> but formatted like %d

Best regards,
Florian

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System