LEGACY System Utility v1.0

Don, could you elaborate a bit more? When you are observing dropped commands from the ARC, I understand that your computer is still connected to your LEGACY base via a USB-serial cable. Is the Legacy System Utility program still running when the ARC playback seems to be interrupted? If yes, please try quitting LSU and try your ARC playback again.

thanks,

Rudy

I bet that isn't true...  I like and respect some of the naysayers but sometimes a person needs to see (or hear) the same info packaged in a different way.  They are somehow able to connect with it from one presenter and not another.  So, I think there is plenty of room for a Legacy book.

Maybe a pamphlet?

This is to be expected.  The transmit side from the computer is clashing with the transmit from the ARC.  You have two RS-232 transmitters both trying to drive the receive line of the command base.

Simple solution, unplug the computer connection.

The PC was powered on and the LAS utility was NOT running . Just thought I would post this to warn others like me who bought a 25ft cable and tried connecting it permanently. Might take a while for them to realize that their Legacy system isn't always responding, and when they do they might no attribute the problem to just having the USB cable connected. 

That's what I thought. I think the computer / keyspan periodically sends a signal even when the utility is not running.  It's not a big deal to leave the USB cable unplugged.

However, these are the types of problems that can drive you crazy when you don't know the source.

Actually, the computer doesn't have to be sending anything.  RS-232 is always active, the output will be driven when no data is being sent.  Even if you exit the utility and leave the port idle, it can still screw up other reception to the command base.

Isn't the ARC the only accessory device that drives Pin 3 (Data into Base)?

Dale, the ARC is the only one that immediately comes to mind.  I would suspect that stuff like the TPC or BPC wouldn't have a problem with the computer plugged in.

Since I don't have an ARC, I am not affected by this issue.

I have both the DCS base and a TTL-serial converter simultaneously connected to the Legacy base via the Legacy Y-cable;  both devices seem to transmit to the Legacy base fine.

In theory, you could work with both connected if you used a "diode or gate":  use diodes to prevent each device form pulling the line up when idle.  Then you'd have to have a weak pull-up to 12V (5V for original TMCC base) to hold the line inactive (high) when neither computer nor ASC was transmitting.

Perhaps the Legacy Y-cable or the MTH DCS cable has some of this voodoo to make things work.

I am curious about the loading on the Legacy base.  Are you saying that you drive 8 TPC's, and also some ASC's and AMC's (how many of each?) with the Legacy Base serial output?

Sorry - I exaggerated.  I have 7 TPC’s, 3 AMC’s, 2 ASC’s, 1 TMCC Gantry Crane and an ASC. I also have 2 SC-2’s which are not connected to the serial cable. I’m hoping I can still add the new Smoke Loader and maybe another ASC.

Dale's eyes are rolling!   I'm surprised all of that is working on the Legacy base!

We've had some reports of "hey, mine drives a warehouse of serial inputs...", my head is wondering too since I did some careful testing of driving just one TPC and a Z Stuff switch driver and noted the limitations of the Legacy base compared to the TMCC base. I do think there might have been some differences between the old TPCs and the latest ones...of course there are, but differences that adress this loading issue.

I guess I should add that my legacy base alone can’t drive really more than 6 devices reliably. You can get 7 devices working but one drops out every so often. After a long fight with Lionel Customer Service who indicated that only 3 devices are officially supported, I decided to take matters into my own hands and purchased a 232LBR9 signal amplifier from B&B electronics.  I now have 14 devices connected to one legacy base and working flawlessly.  I don’t know what the limit is with the signal amplifier, but I’m pretty sure I can add a few more devices without a problem.

Lionel insisted that I was the only one who had an issue with the limitation. It seems to me that comprehensive testing of serial based devices was left out of the development loop for legacy.  I don’t understand why I am so unique.  I use a TPC for every block, and a serial device to control every accessory.  It’s not hard to get to 14.

I'm sure it's VERY easy to exceed the official maximum of three!

Chuck, my hand-drawn schematic for the TPC shows a 2.0Kohm resistor in series with the optoisolator's LED.  Unfortunately, my data sheet for the H11L1 does not give a nominal "ON" current, just the worst case of 1.6mA.  The LED voltage is probably about 1.1V.  I use 3.5V as the minimum for the serial drive line, and this would provide 1.2mA of current, not enough for the "worst case" parts.  

On the other hand, the Transfer Characteristics graph on the data sheet indicates an "ON" current of .9 mA, presumably a nominal value.  This would require an input of 2.9 volts.

For Don's case of 14 devices, if we assume that they are all like the TPC and use the nominal sensitivity of .9 mA, that would be 12.6 mA of drive current.  I tried to build an equivalent simulated load by using a 150 ohm resistor (2000/14 = 143 ohms) and two germanium diodes that gave a forward drop of about .9V at 12 mA.  For my Legacy Base with this load the output voltage sagged to 2.1V, with only 1.4V across the resistor.  That is .7mA per device.  That would be marginal at best.

Does that mean you are impressed that I am driving 14 devices?

No, it means that you could have saved me some time if you had mentioned that you are using a booster.  I should have remembered that from your previous posts.

I manufacture a booster that will drive more devices than the old TMCC Base, and it is only $40.  Your booster seems to be doing a good job for you.

On the good side dale, you've nicely characterized the output of the Legacy base.

I believe Lionel management knows that using the driver chip they chose was a mistake, but it is not easily corrected.

I have not yet widely advertised my MANCO Booster because I wanted to complete the field testing with the first dozen units.  I hope that the LUG meeting at York will give my product some good exposure.

One advantage of my unit is that it has an additional direct feedthrough 9-pin connector so that devices such as computers running the new Legacy system utility can be easily plugged in without disturbing the accessory port.

Don, as I recall, when I looked up your unit, I didn't see any specifications that indicated how much output current to expect.  Do you have any additional information of that type?

The supply voltage is specified at +12 to +16 vdc at 40 ma MAX.

That kind of says it somewhat. They are only trying to drive the cable capacity (50 feet spec) at some highest baud rate.

I did not - it's not a Y cable. Pin outs are different on the one end. I think they say to use the black cable because the keyspan converter won't plug directly into the legacy base because of the lugs. I used a straight Y cable.  The problem is hard to detect because most commands go through.

Great discussion.  Dale, your website rarely comes up.  Lots of useful info when I can get there.

I was hoping to see an update by now, maybe soon??

Dan

Try it with the original Legacy Y cable. As I understand it, the computer connection will then be using a dedicated serial port into the Legacy Base and the rest of your accessories (specifically, the ARC) should function correctly without having to unplug the computer. 

rudy

director of audio

Lionel, LLC

That's a receiver chip, I think the issue here is the drive capability of the boxes.  That would probably be a the matching SN75C188 given they used it's stable-mate.

This is the likely driver and it's drive capability.

SN75C188 Datasheet

In response to Rudy, and thanks for the info too...

The manuals for these devices could include in the description at least a block diagram and more technical descriptions. I think it's time for that kind of information in the manuals.

That's a receiver chip, I think the issue here is the drive capability of the boxes.  That would probably be a the matching SN75C188 given they used it's stable-mate.

This is the likely driver and it's drive capability.

You are correct in your assumption. The board has 89’s on one side and 88’s on the other.

Makes sense, I've used those chips on a number of boards, and I don't recall ever not using both sets, we always wanted to talk both ways.

Try it with the original Legacy Y cable. As I understand it, the computer connection will then be using a dedicated serial port into the Legacy Base and the rest of your accessories (specifically, the ARC) should function correctly without having to unplug the computer. 

Rudy,

It works fine either with the Lionel cable or my Y cable as long as I don't connect the USB to the computer. However, the goal was to have both the serial devices and the computer connected at the same time....

This is not a big issue as the USB cable is easily left unplugged when not using the utility. However, it would be a problem if you were to develop a PC program that acts as a virtual CAB-2. Wouldn't it be useful to have a program that can both issue and and detect commands? Think about what you could do with the capability to automatically issue a sequence of commands when a specific sequence of commands is detected.

In the interim, I’ll settle for a couple of black modules and some more functionality in the utility.

As I understand it, when using the black LEGACY Y cable, you can leave the computer/usb serial connected all the time without conflicting with ARC playback. 

Black modules are coming!

Agreed, that's an excellent idea.

As I understand it, when using the black LEGACY Y cable, you can leave the computer/usb serial connected all the time without conflicting with ARC playback. 

I'm missing something here... How can you plug the keyspan into the black cable and the serial cable connected to the arc? There is only one port on the legacy base, and the other end of the black cable is not the right gender, and is wired differently.

Are you assuming I have a TMCC command base?

Ah, I see. I didn't think you were using a TMCC command base. Let me look into this further. I don't actually have an ARC in-hand, so please excuse me overlooking what sounds like a connector-gender issue.

rudy

When the USB cable is unplugged, the RS-232 interface doesn't have any power, which is why it's not trying to drive the outputs.

Black modules are coming!

Wouldn't it be nice if Lionel handed them out as chachkies at York?  

Don, it looks like you booster should be able to source somewhere between 5.5 and 19.5 mA, depending upon the chip and conditions.  I am inferring that the normal output current could have the same maximum range as the short circuit current.

I test my devices at 70mA output with a minimum output voltage of 3.5V.  I only buffer Pin 2, the pin that drives accessories and power controllers.