On 09/27/2013 10:43 AM,Gregg Eshelman wrote: > On 9/26/2013 4:48 PM, Peter C. Wallace wrote: >> On Thu, 26 Sep 2013, Thomas Kaiser wrote: >> >>> Date: Thu, 26 Sep 2013 23:33:53 +0200 >>> From: Thomas Kaiser <c...@kaiser-linux.li> >>> Reply-To: "Enhanced Machine Controller (EMC)" >>> <emc-users@lists.sourceforge.net> >>> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >>> Subject: [Emc-users] Homebrew BOB >>> >>> Hello >>> >>> I read this page >>> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?About_Charge_Pumps. >>> >>> What is needed to make sure the BOB is only active when LinuxCNC is up, >>> running and healthy? >>> >>> When LinuxCNC is not running, some outputs are in the wrong state. >>> Therefore, I would like to enable the BOB only when LinuxCNC is running >>> and out of Emergency Off. >>> >>> I use a 5i20 Mesa PCI card with a homebrew BOB. >>> >>> Thomas >>> >> You can certainly make a chargepump, but it may be simpler for the BOB to >> just >> use the default I/O state of the 5I20 outputs when linuxcnc is not running >> (pulled up to 5V with 3.3K pullup resistors). Because of this, FPGA outputs >> should be assumed to be active low. Unlike a parallel port that may be probed >> by the BIOS at startup so have undefined states, the FPGA pins are defined at >> startup and after a watchdog bite (they will be pulled high) >> >> Peter Wallace >> Mesa Electronics > My plan is to use a BRS, also known as a Big Red Switch, to shut off > power to the BOB and motor drives while the computer is booting or not > running CNC software. Simple technology that works and is cheap. ;-) > It's easy and cheap, but not failsave....
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