Asking 'what if someone changes the gearbox when the machine is powered down?' is the same as asking 'what if the user puts the wrong tool in the spindle?' when the manual tool change comp asks for a tool change. At some point in time you must tolerate the user being responsible for providing some feedback regarding the machine state, and we draw that line in a different place than you do. I think a microswitch is great for the retrofit of one machine for personal use, but Matt S and I can't justify the cost of the switch and wiring, let alone the cost of the support, on the machines that we deal with. Please realize that I'm not complaining about the lack of persistence, just pointing out that I think it's a valid use case.
That brings up another example of persistent hal data - when I shut my machine down, it knows what tool is in the spindle. When I fire it back up, it thinks the spindle is empty. I suppose we could RFID tag our tool holders like Sam S does.... Rogge >Seb's point is still relevant. The scaling of motor speed >to shaft speed depends on what gear the gearbox is >actually in - that involves the physical position of pieces >of metal, not bits stored on a disk. > >If a design is based on having the gearchange component >remember that the gearbox was in low gear when the >machine was last powered down, it is only a matter of >time until something goes wrong. What happens if >someone manually changes gears while the machine >is powered down? > >In this specific example, the "persistance" is done by >the actual gearbox, and the component ought to get >its state from the gearbox (by microswitches or >whatever else). Adding persistance to the HAL >component means that you are storing the same >thing (gearbox setting) in two places - the box itself >and the HAL component. It is inevitable that sooner >or later they will get out of sync. ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
