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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Potential failure mode with pmacAsynMotor |
| From: | Emma Shepherd <[email protected]> |
| To: | "[email protected]" <[email protected]> |
| Date: | Wed, 18 Jun 2014 04:16:35 +0000 |
|
Hi everyone,
I've recently come across an issue with the pmacAsynMotor driver that I thought I should share, as the consequences can be quite severe! The driver is designed to support homing onto a limit ('flag high'), which requires limits to be disabled (by setting the appropriate bit of ixx24) in order to work. Since this is quite a dangerous thing to do, we have been typically setting up homing to capture on the release of the limit instead ('flag low'). However, I've discovered that if you have got the homing direction set incorrectly (e.g. -ve direction when homing off the negative switch), this results in limits being disabled and the motor driving through the switch. You can turn off this behaviour by commenting out the #define REMOVE_LIMITS_ON_HOME, but by default this is included so I'm just letting people know in case they are not already aware of it! If other people do want to use the feature of disabling limits, I think it would be worth revisiting the driver to make this safer. For example if the home type is 'flag low', disabling limits should not be necessary, so we could at least check for this case. Cheers, Emma |