The Microship Status Reports

In This Issue:

New Toys
The Heartbreak Of Datacomm
THE AuXBAR IS ALIVE! NOISE NOTES (by Steve Sergeant)
Miscellany

New Toys

Today's mail brought a pair of 68HC24 port-replacement units from New Micros, as well as four PLCC sockets for those and the Mitel video chips. The PRU's are necessary on some of the controller boards to add two parallel ports -- we installed one leftover from the Winnebiko II on the Audio Crossbar and it simplified things tremendously.

Also today, I arranged for shipment of the Sharp LQ6NC01 NTSC-compatible color LCD panel. This 6" diagonal color screen will be the display for the Ampro PC (the control system console), as well as the helm video monitor.

And in the email-basket, a self-extracting archive of 37 files arrived from Bill Muench -- his FORTH multitasker, comm tools, test files, and downloader scripts! More learning curves ahead, as soon as I deal with....

The Heartbreak Of Datacomm

Yes, once again, serial communications has ruined an evening. I worked with Henry Xia for about three hours tonight, trying to get the 2-channel serial board to behave on the nav system controller. It uses one of those complex do-all ACIA chips from Rockwell, and the first hurdle was the learning curve -- after which we got it receiving reliably from a nearby laptop.

Transmit is something else again, and even though we can make it echo received characters (proving that all drivers and cabling are good) and even though we can obviously talk to the chip... we can't seem to make it actually transmit any characters from the host. Maddening. I hate computers. However...

THE AuXBAR IS ALIVE!

I mentioned last night that the Audio Crossbar was on the verge of going online, and after mounting all the boards on a substrate today and whipping up a power connector I handed it over to Jason. Hesitantly, he sent it a RESET and I saw the pulse on the logic probe; emboldened, he sent a CONNECT command and voila! The CD player's output blared out of a little amplified speaker! Another command, and the music was replaced by the NOAA weather report from a small scanner. All quite wonderful. Now we need some textual front-end tools that let us talk to it by human-readable device names instead of cryptic channel numbers, more audio devices for testing, some work on noise minimization, fine-tuning to normalize signal levels within the network, and bus cabling to link the two 16x16 boards.

Steve Sergeant, an audio engineer with Sony, designed the analog parts of these boards during the BEHEMOTH epoch, and he has offered to consult on related issues if people route their questions through me. Steve sent a note about noise and interference to Frank (the noise czar) -- since this is an issue that will affect everyone on the project, I repeat his comments here...

NOISE NOTES (by Steve Sergeant)

In my experience, noise control has a lot more to do with grounding, proximity, and power supply decoupling than it does with shielding. The simplest statement about it I can make is to think about your system in terms of where the currents flow in the power and ground systems, always keeping in mind Kirchoff's current law. In other words, if current flows somewhere, it's got to eventually get back to where it started via some path (hopefully not through the input stage of an unrelated component).

Now is the time to think about grounding schemes -- and to figure out how the grounding characteristics of various devices will affect your system. For example, does some device have a DC-DC converter that introduces an AC difference voltage between the power supply side ground connection and the signal side connections?

You should be intimately involved in decisions about ground paths before commitments are made about how to wire-harness the system: Whether to chassis-ground a particular module, whether to add additional decoupling or filtering to the power supply connections, whether the adjacency of different kinds of devices appears problematic, and on which signal lines do grounds get lifted or connected (and on which end). I would say that now is not to soon to begin analyzing the components of the system for these issues.

Miscellany

Finally, a few other quick notes on matters various...

Frank, who seems to be getting involved in all sorts of aspects of this, tested my old 3M SCSI tape backup unit and my NEC CDROM drive on his Mac. Both seem to work, and he spent part of the day mounting the tape machine on an aluminum panel so we can start following sensible backup procedures instead of trusting that the fates will be kind to my precious data.

We're currently trying to decide how to handle the network publishing issues related to this project. As you may know, we have a World Wide Web server and a Gopher server running on the Tadpole SPARCbook (nrl.ucsd.edu), as well as the ftp site at ucsd.edu. Much discussion is presently afoot concerning what should be on these and whether it can eventually supplant the infrequent mega-postings to the nomadness alias. We may even include these status reports, since many people want to track the project but grow weary of 2-3 month gaps between major listserv postings (and I grow weary of dealing with a hundred or more mailer daemons each time I do one).

Print media update: watch the San Diego Union sometime this week! Rumor has it that we may even get color photos...

Finally, if you are a UCSD student and you never followed up with any communication (like the questionnaire) after initially being added to this mailing list, you may be dropped soon. I keep the industry/friends part of the alias fairly well tuned, but there are some unfamiliar names among the 71 students currently receiving these reports. You can help me by letting me know if you're NOT interested; we'll do a note to everyone we haven't heard from to give you one last chance before selecting your address and hitting command-X...

On that grim note, cheers from the lab! ;-)

Steve