I have a HAL which is detecting a false edge when loading LinuxCNC. I have AM882 drives which have an Alarm signal output, and an Enable signal input. Alarm is active-low, Enable is active by default unless LinuxCNC deasserts it, all goes through a 7i92 card. The Alarm signal is tied to its automatic stall detection. If tripped, it disables the STEP input, and only cycling Enable pin resets the drive. The Enable pin also disables the motor current output entirely, which is undesirable, the Z will drop. Initially I had Enable go inactive during estop but it caused the Z to fall for no good reason. Arguably less safe. You have an emergency, bit is spinning, you hit e-stop, the Z falls with the motor still going.
I just simplified it in HAL as "if the estop-assert AND Alarm-assert have a posedge, trigger a one-shot to deassert the Enable signal for 0.25 sec". It mostly does what I expect! However, when I boot up LinuxCNC, Enable deasserts for 0.25 sec and the Z falls a bit, I definitely don't want it to do that without Alarm being asserted. At the time, the drivers were already physically powered and Alarm is NOT asserted (low) for sure. I presume the first servo-thread cycle has a glitchy value on startup, probably the 7i92 itself. I'm not sure what actually does that, the one-shot has to have a posedge to start the one-shot, not a level. If the HAL saw Alarm pin as low (asserted) during booting and the first cycle of servo-thread saw its correct value (high, deasserted), that should NOT trigger the one-shot. Wrong edge. Any idea? Danny ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
