RE: fast epid

["Mark Rivers" <rivers@cars.uchicago.edu>]

Hi Pete,

 

Here’s a message I sent to Philip Taylor at Observatory Sciences recently in response to a similar inquiry.  I’ve included the attachments from that message as well.

 

Mark

 

 

Hi Philip,

 

There is no more documentation on the fast feedback, that needs to be done.

 

I've attached an example .template file.  The 7 strings parsed are macro parameters to the fast_pid_control.db file.

 

INPUT:  The name of the asynPort which provides the readback

INPUT_DATA: The asyn "drvInfo" string which is used to identify the data parameter on the asynFloat64 interface.

INPUT_INTERVAL: The asyn "drvInfo" string which is used to identify the input interval parameter on the asynFloat64 interface.  This is a time in seconds beween data samples.  The input driver must provide this number.

ICHAN: The asyn "addr" field for the input driver, i.e. which ADC channel, etc.

 

OUTPUT:  The name of the asynPort for the output signal

OUTPUT_DATA: The asyn "drvInfo" string which is used to identify the data parameter on the asynFloat64 interface.

OCHAN: The asyn "addr" field for the output driver, i.e. which DAC channel, etc.

 

The DT field of the EPID record is used to control how often the feedback is done.  It is always an integer multiple of the input callback interval.  If the multiple is greater than 1 then averaging is done in the device support.

 

The SCAN field of the EPID record is just used to control how quickly a "snapshot" of the actual PID values are done.

 

I've attached screen shots of the pid_control.adl screen, the pid_parameters.adl screen and the pid_plot_readback screen.

 

These were all done with the first PID record in the template file.  This is an IP330 input channel 0 connected to DAC output channel 0.  I changed the setpoint (red) and you see the ADC input respond (blue).

 

I found a bug in the DAC128V driver while putting this together, and have committed a new version here:

 

https://subversion.xor.aps.anl.gov/synApps/dac128V/trunk/

 

Let me know if you have more questions or problems.

 

Cheers,

Mark

 

 

 

 

---

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of peter.leicester@diamond.ac.uk
Sent: Tuesday, November 23, 2010 11:33 AM
To: tech-talk@aps.anl.gov
Subject: fast epid

 

Can someone enlighten me as to how to initialise the latest version of the fast epid record?

 

I used to use the following but the INP field has changed in the latest version

 

record(epid, "BL18I-OP-DCM-01:FPMTR:FFBS3") {

  field(DTYP, "Fast Epid")

  field(INP, "@ip330 6 DAC1 0")

 

From the code I can see there are an additional 3 fields in the INP so it now requires all of the following

 

field(INP,”@<inputName> <inputChannel> <inputDataString> <inputIntervalString> <outputName> <outputChannel> <outputDataString>”)

 

So what are inputDataString, inputIntervalString, outputDataString?

 

I guess there is an example somewhere?

 

Thanks

 

Pete Leicester

Diamond Light Source

 

 

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Attachment: pid_fast.template
Description: pid_fast.template

Attachment: pid_control.png
Description: pid_control.png

Attachment: pid_parameters.png
Description: pid_parameters.png

Attachment: fast_feedback.png
Description: fast_feedback.png