RE: ISEG EHS device support on the Raspberry Pi Computer

[<peter.owens@stfc.ac.uk>]

I would have thought the "%8R" stream device converter would do the job. 

-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Florian Feldbauer
Sent: 11 September 2012 14:46
To: Mark Rivers; EPICS tech talk
Subject: Re: ISEG EHS device support on the Raspberry Pi Computer

Hi,

thanks for your replies. Writing an asyn driver seems a pretty good idea.

But for the EHS modules from ISEG, I don't think StreamDevice would be 
feasible.
Maybe I'm biased due to our old CAN interfaces.
Up to now we used asynDriver and StreamDevice to control these modules. 
But our CAN interfaces were in principal
RS232- or USB-to-CAN converters which read/write ASCII-Strings. Every 
single byte from the can frame was coded as 2 digit hex value
separated by blanks (somethink like "ab 24 1f 05").
The EHS modules use 32bit float values for currents, voltages and 
temperatures. So we needed to convert a IEEE754 32bit float
to something which stream could write like "%02x %02x %02x %02x", or the 
other way around.

Therefore I think a device support for this modules would be more feasible.
Sure, if we write our own asyn driver one could think about an interface 
which reads/writes bitstreams, so we don't need such a conversion.

Best regards,
Florian


On 09/10/2012 04:53 PM, Mark Rivers wrote:
> Hi Florian,
>
> I would encourage you to consider whether you should write device support at all.  I am copying Bruno on this as well, because I meant to respond to his earlier thread "aiRecord conversion" with a similar comment.
>
> Instead of writing device support you should really consider writing an asyn driver.  If you do that then device support is done for you, and you don't need to worry about all the details of how records interact with device support.  Writing an asyn driver is actually quite easy.  There are many advantages:
>
> - Support for synchronous and asynchronous devices requires a single-bit change in your driver's registration.
> - Support for I/O Intr scanned records is easy.
> - The device support is already debugged.
> - You get the asynTrace capabilities for standard debugging support.
> - You free the developer to use whatever records they want, rather than only the records you support in your device support.
> - If you use asynPortDriver as your base class most of the details asyn are hidden from you.  You don't need to worry about registering the port, registering the interfaces, how to do callbacks, etc.
>
> In your case you might also be able to use StreamDevice.  I don't know enough about the CAN interface to know if this is feasible or not.
>
> There are lots of examples of asyn drivers, including testAsynPortDriverApp in the asyn package, the Modbus driver, and many other drivers in the synApps package.
>
> Mark
>
>
> -----Original Message-----
> From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Florian Feldbauer
> Sent: Monday, September 10, 2012 6:24 AM
> To: EPICS tech talk
> Subject: ISEG EHS device support on the Raspberry Pi Computer
>
> Dear all,
>
> at Bochum university, we have developed a CAN bus interfacefor the
> Raspberry Pi computer [1]
> using the SJA1000 stand-alone CAN controller.
>
> We are using this interface to control the high voltage power supply modules
> EHS 8 620p-F and EHS 8 210p-F from ISEG [2] via the crate controller ECH238.
>
> I have programmed a device support for these high voltage modules based
> on our Raspberry Pi Can interface.
> You can find the sources for the device support as well as the schematic
> of our CAN interface on github:
> https://github.com/ffeldbauer/epics_RPi_can
>
> I will upgrade this repository with a device support for our Wiener VME
> crate, and some custom hardware.
> The VME crate has an CAN interface which can be used to read out
> voltages, currents, temperature and status of the crate.
>
> Up to now the driver support in EPICS is only synchronous. Is there any
> documentation on how to program an
> asynchronous driver support? For some other devices we would need an
> asynchronous support.
>
> Best regards,
> Florian
>
> [1] http://www.raspberrypi.org/
> [2] http://www.iseg-hv.com/en/products/product-details/product/21/
>


-- 
-------------------------------------
| Dr. rer. nat. Florian Feldbauer   |
|                                   |
| Institut für Experimentalphysik I |
| Ruhr-Universität Bochum           |
| Universitätsstr. 150              |
| D-44780 Bochum                    |
|                                   |
| Office: NB 2/173                  |
| Phone:  (+49)234 / 32-23538       |
| Fax:    (+49)234 / 32-14170       |
| Web:    http://www.ep1.rub.de     |
-------------------------------------

-- 
Scanned by iCritical.