Peter C. Wallace wrote: > On Tue, 23 Sep 2008, Eric H. Johnson wrote: >> Sebastian, >> >> Can you check to see that the pwmgen.enable is working properly. I was >> running samples all day (which looked great, btw, after resolving a very odd >> problem) so I did not have a chance to do much testing. I am now dropping >> the enable when the shutter closes, however the pwmgen.value is still >> getting values. The laser was still coming on even when the enable was low. >> >> I will try setting the frequency of the pwm from the latest update and >> hopefully test that tomorrow. > > Well I'm not Sebastian, but I know why you are seeing that behavior: > > The enable register was designed for our PWM and Analog output daughter cards > so it doesnt actually affect the PWM output, its just a group of (active low) > output bits used to enable the daughter card output channels. I can certainly > change this behavior so that the PWM output is forced low when a channel is > not enabled (cheap in terms of FPGA hardware). The active low enable output > is > used to guarantee that the motor drive outputs are off at power up (or > watchdog bite) > > I dont think there are any bad side effects of forcing the PWM output low if > disabled, but there are possible bad side effect of using a active high PWM > output without the enable (Laser is on high at power up unless you have some > other active low enable signal)
The driver & firmware currently communicate the pwmgen.XX.enable pin to the /Enable IO pin on the IO connector (I just re-checked this). Peter's got a good argument for why the value of the PWM pin shouldnt matter to the downstream equipment if the /Enable IO pin is high. Eric, how are you handling the start-up condition (and potentially the watchdog condition) that Peter is describing? What would it mean to keep the PWM IO pin low if the .enable HAL pin is low? Should the FPGA *not* let the PWM pin go to high-impedance/pullup at bootup and at watchdog bite? -- Sebastian Kuzminsky "Hey look, it's a man!" "A meatie! Look at the meatie!" "Hi meatie! How's the weather?" -- from "Cathedrals" by Alex Hardison <http://www.flurb.net/5/5hardison.htm> ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
