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.
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