On Mon, 2010-12-13 at 16:36 +0100, dambacher-retrofit.de wrote: > Am 13.12.2010 15:56, schrieb Stephen Wille Padnos: > > I don't think this is a concern. People who have hardware that removes > > the need for a base thread very likely also have a watchdog feature in > > their hardware. I know the Mesa and Pico products do, and I believe the > > Pluto does as well. (I'm not sure about Motenc and STG) > Motenc has a watchdog circuit barking at 8 or 16ms (selectable) if you don't > write DACs or the wd register. > > > - Steve
Just thinking out loud. I see the PWM controller has this in the doc's: " Jumper JP4 can be selected to enable or disable the watchdog timer on the board. When enabled, the watchdog will force the board into Emergency Stop mode when the rate generator registers have not been written to in 20 mS. " I guess one issue is that the integrator will need to make sure that the PWM controller e-stop signal out is connected to all of the e-stop slaves and not just EMC2, because if the controller initiates a watchdog fault, we can't rely on EMC2 to handle it. A proper e-stop system would commonly be set up this way, so it shouldn't be a problem. Also, this watchdog only validates EMC2. The Pluto doc's are a little more interesting: " Before configuration and after properly exiting emc2, all Pluto-P pins are tristated with weak pull-ups (20kΩ min, 50kΩ max). If the watchdog timer is enabled (the default), these pins are also tristated after an interruption of communication between emc2 and the board. The watchdog timer takes approximately 6.5ms to activate. However, software bugs in the pluto_servo firmware or emc2 can leave the Pluto-P pins in an undefined state. " An independent wathcdog might be prudent. With the Motec one can pet the dog internally with dac-write (from EMC2) or from an external source (using watchdog-reset as an input rather than output)? I found this for Mesa's Hostmot2: " ... Watchdog The HostMot2 firmware may include a watchdog Module; if it does, the hostmot2 driver will use it. The watchdog must be petted by EMC2 periodically or it will bite. When the watchdog bites, all the board’s I/O pins are disconnected from their Module instances and become high-impedance inputs (pulled high), and all communication with the board stops. The state of the HostMot2 firwmare modules is not disturbed (except for the configuration of the IO Pins). Encoder instances keep counting quadrature pulses, and pwm- and step-generators keep generating signals (which are *not* relayed to the motors, because the IO Pins have become inputs). Resetting the watchdog resumes communication and resets the I/O pins to the configuration chosen at load-time. If the firmware includes a watchdog, the following HAL objects will be exported: Pins: (bit in/out) has_bit: True if the watchdog has bit, False if the watchdog has not bit. If the watchdog has bit and the has_bit bit is True, the user can reset it to False to resume operation. Parameters: (u32 read/write) timeout_ns: Watchdog timeout, in nanoseconds. This is initialized to 1,000,000,000 (1 second) at module load time. If more than this amount of time passes between calls to the pet_watchdog() function, the watchdog will bite. Functions: pet_watchdog(): Calling this function resets the watchdog timer and postpones the watchdog biting until timeout_ns nanoseconds later. ... " It seems when the watchdog bites, the controller goes and hides in the dog house (stops communication and tri-states IO pins) until it's told that the coast is clear. It may be that an independent watchdog might be handy here too? Another use for a stand alone charge-pump/watchdog is to validate other hardware like limit switches by having an oscillator at the switch. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Lotusphere 2011 Register now for Lotusphere 2011 and learn how to connect the dots, take your collaborative environment to the next level, and enter the era of Social Business. http://p.sf.net/sfu/lotusphere-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
