On Sun, Apr 22, 2018, 10:10 Gene Heskett <ghesk...@shentel.net> wrote:
>
> ISTR they come unprogrammed, and set to be connected to a parport for
> programming the correct config for your use into it with mesaflash. It
> has a backup recovery that must be used long enough to reset it to
> parport communications IF its been set to talk SPI, which is faster on
> the pi's but not available on *86 machines. Except for the missing spi
> capability on x86 machines, the parport on the x86 motherboard s/b fast
> enough.
>
> But note, and I emphasize this strongly, the 50 pin connectors hook
> directly into the fpga, and noises above 4 volts may blow the fpga's
> buffers, so the surge and noise protection of a 7i42TA, which also gives
> you a handy mechanical terminal arrangement to connect it to the outside
> world, and will protect it from the noise pickup from the stepper motors
> etc. I destroyed several before I understood the importance of that, and
> the one driving my lathe has had functions moved to different card
> outputs because of blown buffers. I actually wound up putting the pi,
> the 7i90, and the 3 7i42TA's in a separate box, and mounted that box to
> the lid of the old rusty box the power stuffs was in. Then my noise
> problems disappeared.
>
> I'm listening. Next week is almost all rig working, I will get at least 1
> 7i42 coming. I downloaded the 7i90 package and didn't see the softdmc. The
> idea of using generic h bridge as the drive really appeals to me as it
> eliminates propietary communication and the associated debugging. Also they
> are $20 shipped to my door in the states so they are easily replaceable
> and can affordably be kept in stock. Finances have been tight , as I have
> been doing mechanical upgrades as well, taking from the auto business to
> build the machine shop.
>
>
>
> But this brings up a second recommendation, which is to establish a
> single bolt as a common ground point, with the commons of everything
> else connected ONLY to this bolt. This is known as a star ground system.
> Stuff connected to the nearest ground often results in having more than
> one ground and that constitutes a ground loop, which acts as an antenna,
> picking up noise from anything radiating it, and this noise can easily
> blow gates in the fpga on the 7i90. That bolt should also be the only
> place the 3rd rounded in the US pin in the power cord is connected, cut
> them off till you've only one left to get rid of ground loops, just
> don't cut the last one!
>
Yes, familiar with star grounding and ground loop isolation. I went to
machinist school out of high school, no one wanted a cocky 18 yo machinist.
I took a job at an electronic remanufacturing facility splitting time
between cosmetic work and repopulating damaged components, we had 4 cets
and a huge engineering library accessable. I have always read a lot , and
was a budding audiophile. At the time popular electronics was my favorite
magazine. They paid college tuition at that job so I got a semester of
electronics theory in before the ways of an 18 yo boy got in the way of
that job. When I relocated to Missouri there were no electronics places in
these here hills to work. Realizing the importance of education I sought
employment as a dealership technician. 15 years of 2-3 classrooms a month
and I have a very good understanding of practical application. I worked a
couple years at an aerospace contractor, till laid off then went back to
school in a CNC focussed program. Went back to upstate NY to take care of
my father and ended up managing 28 fellers making chips.
>
> To give some credence to what I'm writing, I have never been a working
> machinist altho I've had my hands of the cranks of a lathe many times in
> my 83 years, but I am a Certified Electronics Technician and have used
> that knowledge to earn a liveing since I was about 14 years old. I got
> interested in broadcasting, and spent the last 22 years of my working
> time with an office door plaque saying Chief Engineer on it at some tv
> station. And I have the instruments to measure, and visually show me
> that noise.
>
> One thing I did when configuring this lathe, was that since the firmware
> you use mesaflash to install puts _most_ of the "canned" functions on
> the first of those 50 pin connectors, 24 i/o's per connector, when I
> started adding the gingerbread that needed gpio pins's, I started at the
> top of the 3rd connector, and I've added quite a bit of stuff, and
> figured I'd stop when I had used what was in the middle. That way I
> wasn't moving stuff around once it was set, and thats worked out well. I
> still have plenty of gpio's left yet, to hook up coolants, lubrication
> squirts etc that I haven't bought the hardware to do it with, yet.
>
This seems pretty sound, I have an atx case here I believe I will use.
So if you have noise problems, you will need a scope fast enough to see
> the noise, and that means 100 mhz of bandwidth, not one of these $40
> toys. Be on the lookout for used Hitachi v-1065's on ebay. Now 35 years
> old, somewhat computerized so its calibration has stayed valid, much
> moreso than tektronix stuff, its a decent tool yet. Mine has spent many
> hours in a twin piston pounder airplane as I've also played visiting
> fireman at other broadcast facilities, so I've had to open it and
> retighten all the framing screws that vibrated loose, and the
> pushbuttons are getting flaky, but the tube is still fairly bright and I
> can believe what it tells me. Dual trace, fully triggered of course.
>
Definitely on the list, but not high enough yet, more concrete needed in
> the shop and a couple other machines to get functional. I did order a light
> dimmer to reform the caps on my old tectronix. It's going to have to do for
> a bit. I am really interested in a decent handheld as it would do
> multitudes of tasks. Especially on the auto side of life.
Would there be harm in powering and programming the 7i90 with my laptop
without using any I/o just to familiarize myself with the board ?
>
>
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