Experimental Physics and
Industrial Control System

Peter Milne <[email protected]> · Wed, 14 Aug 2013 09:14:52 +0100

Hi Peter

If your use of gpio is the "switch a bit on, switch it off sometime

later" type,

then the linux kernel gpio support will probably do it for you:

eg from the shell control would be:
echo 1 > /sys/class/gpio/gpio100/value

We use that interface extensively with an ioc; we wrote a very thin

layer of device support that reads/writes single values from/to a

virtual file and fits it into an appropriate record. A small set of

abbreviations makes the db support palatable.

eg for BO record type, in the device support:

/** @file devBoAcqHost.cpp Device support entry for BO records
 *
 *  Created on: May 3, 2012
 *      Author: pgm
 *      BO:
 *      INP = path to knob, write 0 or 1.
 *      specials:
 *      %g KNOB : /sys/class/gpio/KNOB/value
 *      eg %g gpio100
 *      %l KNOB : /sys/class/leds/KNOB/brightness {1|0}
 *      eg %l cpsc:1:green:idle
 */

in the db file:

record(bo, "${UUT}:PSU:RESET:${cid}") {
        field(DTYP, "boAcqHost")
        field(OUT, "@%g gpio${gpio_reset}")
        field(DESC, "reset PSU ${cid}")
        field(ZNAM, "OK")
        field(ONAM, "ERR")
        field(PINI, "YES")
}

record(bi, "${UUT}:SYS:exttrg2") {
        field(DTYP, "biAcqHost")
        field(INP,  "@%g gpio22")
        field(DESC, "front panel input WAVTRIG")
        field(SCAN, "1 second")
}

I'd be very happy to send you a copy of the source if you're interested.

Cheers

Peter.

On 14/08/13 08:25, Florian Feldbauer wrote:

Hey Peter,

to access the GPIOs from EPICS you need to write a device support

module using the C-libraries.

Unfortunately there is no good documentation on this topic for

beginners that I know of...

I could provide you my device support for reading out DS18S20

Dallas-1-Wire Temperature sensors using the Pi as a starting point.

Best regards,
Florian

On 08/14/2013 02:09 AM, Peter Linardakis wrote:

Hello all...

We are exploring the idea of using Raspberry Pi for basic digital IO

tasks. Theidea is that we could avoid deploying other IOCs and

possibly wasting many other IOC ports. I have EPICS running on a

Raspberry Pi with a test record DB (soft records only) and it is

successfully communicating across the network. I know how to

directly access the GPIO pins while on the Pi (through C libraries

etc.),but I do not know the first thing about how to get to those

pins through EPICS.

Any advice or direction would be much appreciated.I am relatively new

to EPICS development but am experienced with with maintenance of

EPICS records and the like.

Regards
Peter

Dr PeterLinardakis

/Accelerator Research &Development Engineer/

*Nuclear Physics | Research School of Physics and Engineering*

*Australian National University*

e: [email protected]

p: (02) 6125 2862

--
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| Dr. Florian Feldbauer                |
|                                      |
| Helmholtz-Institut Mainz /           |
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| D-55128 Mainz                        |
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--
Peter Milne			[email protected]
D-TACQ Solutions Ltd		www.d-tacq.com

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System