sharing from DOS woes and solution

It's easy! Just follow the instructions posted all over the web... (e.g. here: http://bbright.tripod.com/information/dosnetwork.htm)

Basically, download a "new" version of "net.exe" (from WFW3.11) and its associated files, it adds the command "net share." It'll complain that share.exe doesn't exist, or wasn't loaded, but they've even got that covered; just ignore the message (you don't need it, according to MS, or create an empty file called share.exe so some other programs won't complain).

If you're setting it up from scratch, those instructions should do it for yah.

BUT! It didn't work on my system (which already had networking set up, just not sharing). I don't know what's going on with my setup... I do know this much: a Google search for the error I'm receiving returns ziltch, nada, literally. It's hard to believe... so here it is:

I try: net share shared=c:\shared

and it replies: "Error 7381: File sharing has been disabled by your network administrator."

(Update: I found the solution. wfwsys.cfg was the culprit, so you can save yourself the boredom of reading below, except at the very end... though there is some useful info re: mapping a drive instead of start - run \\dosMachine\share, etc.).

I've been at this for hours, so you can imagine I've looked at system.ini countless times, and tried everything I've found on the web... (which is pretty limited, since no one mentions this message). I *am* the network administrator dangit! I don't know what's wrong.

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I have since backed up my old configuration and started fresh using the instructions at http://bbright.tripod.com/information/dosnetwork.htm (and many other locations). And have gotten rid of the dreaded "disabled" message. The command "net share" shows the shares, but I can't get my WinXP nor my Mac to connect to it using either the name nor the IP. I can ping it from both machines.

The Mac gives an error almost immediately: "There was an error connecting to the server. Check the server name or IP address and try again." It sounds vague enough, but I tried connecting to an IP I know doesn't exist and receive a slightly different message after quite some time... so it seems the Mac is at least aware of the DOS box (maybe only because it's acting as the DHCP server?)

The XP machine seems to just time-out after quite some time with the ol' "The network path was not found."

Now, I've had trouble connecting the DOS machine when running Win98SE to my Mac shares... that's another story entirely. I read somewhere about an update to NTLM2(?) that was supposed to fix it, but it didn't work for me. So I've been connecting to the Win98 share from my Mac, instead. But now (in DOS) I can't connect either way. I can, however, connect the DOS machine to a WinXP share, and the Mac to the same WinXP share... so at least there *is* a way to transfer files between DOS and the Mac. (The Mac is my main machine). But, I was able to do that long before I started this venture, and I've wasted countless hours to get just sparse nibbles of hope for what would've been a minor inconvenience at most... (so hopefully this diatribe helps someone, now that I've figured it out...)

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I managed to get WinXP to connect to the DOS share. I don't remember exactly how. I did notice that the MS Networking Client created a few entries in system.ini that weren't correct (two entries for protman, so I got rid of one). Also, It wouldn't connect using Start - Run \\dosServer\share. The new error message was something along the lines of "invalid resource." So I tried mapping the drive directly and it worked!

Still can't get the Mac to connect to it, I've tried many different methods: from Connect To Server (in the finder) to using mount through terminal, to using smbclient and others. Each method gave a different error. At one point I got something like "invalid header received from server," and another mentioning something about user-level sharing not being enabled. Anyhow, I chalk this up to MacOS... and someone online said something about SMB probably not being tested too thoroughly on MacOS since "the developer doesn't have a mac" (?). Also mention of Apple disabling some types of authentication due to insecurities (most likely to exist in old DOS networking!) But I dunno.

I guess my goal was to figure out what was *causing* the original error message (sharing disabled by my network administrator), and instead ended up installing the DOS networking fresh (which fixed it). Maybe one of my original networking files had been modified by a net-admin (I acquired this network boot disk from an old job), maybe it was a combination of differing versions of drivers and utilities (the version of net.exe on the network boot disk did not have support for "net share"), maybe something was loaded (or not loaded) to cause the problem. I did notice that the ms network client installer loads two additional drivers in autoexec.bat. I may look into it further. For now, follow the instructions at the link above and do a fresh install (be sure to back up your original files! I have them in two separate directories, also config.sys and autoexec.bat) and look closely at boot messages and system.ini, try mapping a drive instead of using Start-Run, and that's what worked for me.

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FOUND IT!
The file wfwsys.cfg has apparently been customized. You can get a functional normal one from the MS Network Client installation disks (downloadable, see above link).

The modified file serves two purposes I can see so far. One is to disable file-sharing from the machine (yay!). The second (and likely the reason it was modified in the first place) is so a username.pwl file is not created each time the boot-disk is used. Not that it would matter, the pwl file would be saved to the ramdrive and lost with a reboot. I think the main reason is so it doesn't give the message asking whether you'd like to create the pwl file every time you log on.

No shit!?

I closed the page, but I'm 99% certain I read that OnTrack Disk Manager breaks all the current size barriers, supporting 136GB+ drives on systems all the way back to the original PC/AT. Could you imagine an 8088 with a 1TB drive?! Have you even *seen* an 8088?

And I just discovered the setup switch to install Win98SE on a 386. WTF is the world coming to?!

Voltage Regulators 102, Op-Amps 101: AC-coupling!

I built this power supply several years ago, always with the intention of adding an amplifier for the current-sense circuitry.

I used a .01ohm resistor for current-sensing, 'cause I didn't want it to interfere with the output voltage. The resistor was tied in series with the +Vout path.

The voltage across this resistor is measured, currently, directly. So, measurements are 1/100th of the actual value (kinda confusing to read on a multimeter).

So I've been fighting with analog circuitry for a few days to try to amplify this 100x. Seems simple enough with the "ideal Op-Amp." Yeah, right. First things first, I have to consider CMRR (Common-Mode-Rejection-Ratio)... something I hadn't considered an issue.

The differential voltage (voltage across the resistor) varies from 0 to 0.04V (with a 4A load, max for my supply, I want to amplify this to 0-4V). The Common Mode voltage (voltage at the resistor, WRT ground) is 0-24V. We're talking 100's of times difference between CMV and differential voltage. I don't remember my dB conversions at the moment, but I'm pretty sure a 100dB CMRR (which is *excellent*, and nowhere near the ability of standard Op-Amps and resistors) is not nearly enough for this circuit.

So, what's happening? As the output voltage of the power-supply varies, so does the output voltage of my Op-Amp, dramatically. The differential voltage (across the resistor) is being amplified in there, somewhere, I think. But it's completely lost.

This is why Analog circuitry has always let me down. It seems like a simple circuit. Even 2 years' training in EE lead me to believe it would be. Instead, it's a battle at every step. The resistors have to be matched to 0.01% tolerance (HAH! 1% is alot to ask for, even in my vast collection of assorted parts.). The op-amp itself has to be of high-quality... (so much for all these standard LM series chips I'd been meaning to do something with). I wanted to do it with a single-supply (+/GND as opposed to +/-/GND) which was the first difficulty which even a "single-supply op-amp" like the LM324 makes difficult. The list goes on.

Here are a couple references I came across to verify my experimental results: http://www.maxim-ic.com/app-notes/index.mvp/id/1180 http://www.maxim-ic.com/app-notes/index.mvp/id/746

So, apparently, high-side current monitoring is difficult. Let's switch to low-side! Still having issues... Not sure why, exactly. But I'm tired.

So: Op-Amps 101: they work best with AC signals (audio, etc), coupled through a capacitor. Anything else and you're setting yourself up for disaster.
Voltage Regulators 102: Measuring current on the high-side is difficult, to say the least.