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<== Date ==> <== Thread ==>

Subject: Re: "No conversion between src & dest" warning with pcaspy
From: "Wang Xiaoqiang (PSI)" <[email protected]>
To: Jameson Graef Rollins <[email protected]>, "Kasemir, Kay" <[email protected]>
Cc: Epics <[email protected]>
Date: Tue, 3 Mar 2015 19:47:58 +0000
Since this is a pcaspy only bug, I created the report in the project issue tracker.
https://code.google.com/p/pcaspy/issues/detail?id=14

Thanks for the detective work to reveal the bug.

Best
Xiaoqiang

> On 03 Mar 2015, at 18:54, Jameson Graef Rollins <[email protected]> wrote:
> 
> On Tue, Mar 03 2015, "Kasemir, Kay" <[email protected]> wrote:
>> On Mar 3, 2015, at 12:19 PM, Andrew Johnson <[email protected]>
>> wrote:
>> 
>>> On 03/03/2015 11:04 AM, Kasemir, Kay wrote:
>>>> Until the PV is initialized, I get the same 
>>>> 
>>>> No conversion between src & dest types no conversion between event
>>>> app type=16 and DBR type=18 Element count=60
>>>> 
>>>> error.
>>> 
>>> The implication is that pcaspy is presenting an uninitialized channel's
>>> value to the cas as some type which gdd can't convert into to an array
>>> of chars. The answer may be as simple as always initializing the value
>>> of a string channel to be an empty string.
>> 
>> .. which I just found can be done like this:
>> 
>>  self.setParam('ThatPV', [ 0 ])
>> 
>> That seems to work for clients that look for a long string, since they end on the first '\0'.
> 
> Interesting.  I can confirm this works as well.  In fact, just setting
> the initial 'value' to [0] in the database definition does the trick as
> well:
> 
>    'STR': {
>        'type': 'char',
>        'count': 60,
>        'value': [0],
>    }
> 
> Thanks for the sleuthing, Kay.  Maybe we can put together a patch that
> changes how these records are initialized inside of pcaspy.
> 
> I just realized that camonitor is showing worse behavior than MEDM in
> regards to these improperly initialized records; it just hangs with no
> output at all until a valid value has been written to the array.
> 
> jamie.



Replies:
Re: "No conversion between src & dest" warning with pcaspy Jameson Graef Rollins
References:
"No conversion between src & dest" warning with pcaspy Jameson Graef Rollins
Re: "No conversion between src & dest" warning with pcaspy Andrew Johnson
Re: "No conversion between src & dest" warning with pcaspy Kasemir, Kay
Re: "No conversion between src & dest" warning with pcaspy Andrew Johnson
Re: "No conversion between src & dest" warning with pcaspy Kasemir, Kay
Re: "No conversion between src & dest" warning with pcaspy Jameson Graef Rollins

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