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INDI Library v1.7.8 Released (11 May 2019)

Mid year release of INDI Library v1.7.8 comes with a few drivers and improvements to to existing drivers.

Guiding and movement control

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Guiding and movement control was created by ChrisRowland

Hi,
I've been looking at the guiding on the Celestron GPS driver and found some snags.
The most serious is that the first guide command uses the currently set movement rate, after that is started the rate is set to the guide rate. If the rate is set to full speed the mount hares off at great speed for the guide duration. It's the sort of behaviour that confuses users and causes them to believe that guiding through the mount doesn't work.

I could change the movement rate to be done before the start of the guide command but is there any need to do so? I can guide sending commands directly to the mount without using the movement interface at all. Does this violate any principle of INDI? Are clients expecting that the movement rate will be set to Guide if guiding is done?

Chris
3 weeks 12 hours ago #38712

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Replied by TallFurryMan on topic Guiding and movement control

The mount driver I coded recently has to switch to guide rate before guiding because it does not support the generic LX200 pulse guide commands, only timed moves. So I'd say if the hardware has specificities, it's up to the driver to cater for that.
But that only applies to the client interface of the driver: being an interface, the driver assumes a state from what it reads from the hardware and what it reads from the client.
In your particular example, the driver should be aware of the current rate, except if there is another interface that allows the rate to be changed incognito. Thus, if the current rate can't produce the required action, it has to be changed first. Else, it doesn't have to.
In my particular example, the mount doesn't report the rate and I later realized that the guiding rate could be changed from the pad. Thus in my situation, I'd have to prefix all my timed guiding commands with a command setting the guide rate. In the current code I settled on resetting the rate to guiding after a slew.
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2 weeks 6 days ago #38759

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Replied by ChrisRowland on topic Guiding and movement control

I don't want to force how other mounts operate, it's just that with the Celestron driver I have no need to involve the movement controls and the guide controls at all.

Using the Move rate but not setting it until after the command is definitely wrong. Setting rate 9 (4 deg per sec) then issuing a guide command with a duration of 1 second shows this, the mount rushes off by nearly 4 degrees, then when you try to reproduce it doesn't.

I'll keep the move and guide rates separate, it's whay works for my mount and doesn't affect what others do.
2 weeks 6 days ago #38793

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