Hi Dominique,
Sorry for the delay in replying to this, I was on vacation.
I think an easier solution to this problem is to use 2 calc records to
convert the 32-bit integer to 2 16-bit integers, and write those to the
Modbus driver using function 6. Then you don't have to write any C
code, just a simple database.
PowerSupply (longout) -> calc1 (16 LSB) -> longout1 -> Modbus
-> calc2 (16 MSB) -> longout2 -> Modbus
I don't recommend modifying the driver, because a 32-bit integer is not
a standard Modbus data type, and we could end up with all sorts of
modifications for non-standard data types.
Mark
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Touchard Dominique
> Sent: Wednesday, September 19, 2007 8:44 AM
> To: [email protected]
> Subject: Use of waveform records
>
> Hi,
>
> we are working on/with the Epics modbus tcp driver written by Mark
> Rivers. We need to write a 32 bits integer value in a power supply
> command control interface. First we thought to write an asyn32Int
> record with the number 6 modbus function. Immediatly, we saw that the
> driver uses the number 6 modbus function which works only on
> a 16 bits word.
>
> After reading the Modbus Driver Support documentation, we saw that we
> have to use a two value length waveform record.
>
> First question : is this correct ?
>
> Second question : do we have to use the gensub record to manipulate
> values inside a waveform record ? In this case, is there any example
> that shows how to do this ? Could somebody send us an example
> on this ?
>
> Third question : Is a bad idea to modify the modbus driver in the goal
> to write a asyn32Int 32 bits integer record with the number 16 modbus
> function ?
>
> Thanks for your help .
>
> Dominique Touchard.
>
>
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