On Sat, 2010-12-04 at 09:16 -0500, Kenneth Lerman wrote: > I would use a single pin for communication to the host with some variant > of the one-wire protocol used by iButtons. > > It is simple, elegant, and relatively insensitive to timing. > > Ken
USB is attractive because I can get a cheap AVR board with firmware that could work on any PC with terminal software (minicom or putty). All that I am currently looking for is a one time setting of one parameter value, but the more I think about it, I may only need one of a few presets which could be handled by two pins and a dip switch, or a trim pot. I have used SPI for a DAC, but I had to bit-bang it through the parport and it would only work with my HAL component, which is fine for the particular application. One problem is that I made an assumption that I needed to catch the first late edge of the charge pump, and to be more generic, I needed to finely tune the countdown value to match whatever charge pump frequency might be used. If I change the requirement to catching the loss of the charge pump signal within a reasonable time, the parameter tuning goes away. Then I got to thinking about what Slavko mentioned previously, about this is a safety device and I should think in terms of how it could fail. Changing track, again, the charge pump signal may not be the best thing to use, because all it would take is noise on the line to mimic the pump. I think I should make some sort of data pump component, such as send out a byte every servo period, then have the watchdog watcher check for the proper byte. This changes the form of the link between EMC2 and the watcher, and maybe the parameter setting requirements, or lack thereof. This reminds me of a previous project I was considering, but forgot about, which is to use a data stream to fail-safe limit switches. I have more thinking to do, carry on. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ What happens now with your Lotus Notes apps - do you make another costly upgrade, or settle for being marooned without product support? Time to move off Lotus Notes and onto the cloud with Force.com, apps are easier to build, use, and manage than apps on traditional platforms. Sign up for the Lotus Notes Migration Kit to learn more. http://p.sf.net/sfu/salesforce-d2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
