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ProtoTrak plus RS232 communication with laptop

Xrrng3

Plastic
Joined
Sep 30, 2023
Hello all, first time posting. I have been reading for a while now and I'm still having issues. I'm trying to connect a laptop running Win 8.1 with a serial port, COM1 to my prototrak plus. I have the COM1 set to 7,n,1 with no flow control(prototrak manual) I'm using a Null modem cable. I've tried a few different programs, one of which I found in a thread here, by the way, the guy was very clear, but it's just not working here and I'm not sure why and didn't want to wake up an old thread. I've even tried command line, still no luck. Please excuse the mess in the photo. The laptop sees the port when I command line mode COM1, it displays the correct information. I go through the steps on the Prototrack, tape/rs232, 2 for RS232, 2 for send, +/- for file. I set the app on the laptop to receive, I press INC, the display says sending file then OK. But nothing makes it to the laptop. If I missed anything, please let me know. I'm at a loss beyond having a bad cable, so I have a tester coming to see if any data is even leaving the Prototrak.
Thanks
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you possible need handshaking. Many null modem cables disable or loopback the hardware RTS/CTS or DSR/DTR handshaking and only swap the TX/RX lines. This make it seem that both ends of the connection can send and are ready to receive, even when they are not. On slow links, anything that gets through is just luck.
The way to test this is with an RS232 led tester which will show you the state of the lines.
 
Thanks, I'll have an LED tester here later this week and I'll check it out. What should I be watching for when I test the line? And what can I do to deal with this?
Dan
 
there are 3 communication sets:
data RX/TX
handshake 1 RTS/CTS
handshake 2 DSR/DTR
Plug the tester on the prototrack side only and initiate a send if you can. You will see which type of handshaking it uses, sometimes both types are used. THis will also indictate which is the send pin. The null modem adaptor after the tester might fake the handshake enough to get some lights flashing.
On simple old systems, you would next check the computer side the same way. Since the computer has a buffer it does not really need handshaking to stop the prototrack sending, but the prototrack needs to get the right signals to say ready to receive. The computer will often raise CTS to say clear to send all the time, because it is always ready and has a buffer to hold the data.
Now plug the whole lot together and look at the lights. Then initiate a send you should see the handshaking and the data lights flash, they probably wont, because the rx/tx and handshaking need to be crossed over. This check if the null modem cable is full with handshaking or uses loopback handshaking to fake the signals.
For RTS/CTS, the prototrack will raise RTS and the computer should respond with CTS then the prototrack would start sending data and you would see both rx & tx flashing. when finished, the prototrack would drop RTS
 
there are 3 communication sets:
data RX/TX
handshake 1 RTS/CTS
handshake 2 DSR/DTR
Plug the tester on the prototrack side only and initiate a send if you can. You will see which type of handshaking it uses, sometimes both types are used. THis will also indictate which is the send pin. The null modem adaptor after the tester might fake the handshake enough to get some lights flashing.
On simple old systems, you would next check the computer side the same way. Since the computer has a buffer it does not really need handshaking to stop the prototrack sending, but the prototrack needs to get the right signals to say ready to receive. The computer will often raise CTS to say clear to send all the time, because it is always ready and has a buffer to hold the data.
Now plug the whole lot together and look at the lights. Then initiate a send you should see the handshaking and the data lights flash, they probably wont, because the rx/tx and handshaking need to be crossed over. This check if the null modem cable is full with handshaking or uses loopback handshaking to fake the signals.
For RTS/CTS, the prototrack will raise RTS and the computer should respond with CTS then the prototrack would start sending data and you would see both rx & tx flashing. when finished, the prototrack would drop RTS

Again, thanks, I'll see what I can do and report back what I find.
 
Today I tested the cable and it's OK, so that's not the issue. I'm down to the PT unit. I noticed that on the DB25, pin 2 is brown, pin 3 is yellow, and pin 7 is blue. On the plug connecting to the main board, pin 2 is yellow, pin 3 is brown, and pin 7 is blue. This got me thinking, did someone swap those pins to use a standard cable instead of a null cable? I swapped the yellow and brown wires but didn't notice any difference. Those three wires appear to be the only wires other than 4-5 and 6-8 being jumpered.

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no, there are two kinds of RS232 equipment, DTE and DCE. Data Communication Equipment is/was the mainframe computer. DCE is considered the sender of initiator of communications. DTE, Data Terminal Equipment was the old dumb terminal, machine or pc. Since you have a machine and a pc, both are DTE and this is why you need the null modem adaptor to swap the TX/RX wires, otherwise it would be TX->TX and RX->RX. I would have to check the pin numbers, but it looks like the links set the handshaking as always ok to send and receive. When you put the tester on, you will see which cables need swapping. By convention, this is done in the cable, not on the equipment side. Some manufactures do wire outside standard so a straight through or proprietary cable is used. RS232 was a very early standard and was way too loose, much was learned from this standard and the newer ones are much better.
 
no, there are two kinds of RS232 equipment, DTE and DCE. Data Communication Equipment is/was the mainframe computer. DCE is considered the sender of initiator of communications. DTE, Data Terminal Equipment was the old dumb terminal, machine or pc. Since you have a machine and a pc, both are DTE and this is why you need the null modem adaptor to swap the TX/RX wires, otherwise it would be TX->TX and RX->RX. I would have to check the pin numbers, but it looks like the links set the handshaking as always ok to send and receive. When you put the tester on, you will see which cables need swapping. By convention, this is done in the cable, not on the equipment side. Some manufactures do wire outside standard so a straight through or proprietary cable is used. RS232 was a very early standard and was way too loose, much was learned from this standard and the newer ones are much better.
Yes, I understand that the send and receive need to cross. My question is, did someone before me swap these wires? It seems odd that the wires change pin position between the main board and the DB25 socket. The upper picture has brown, yellow, blue for the wire, and the bottom picture is yellow, brown, blue.(bottom plug is facing the other direction).

If I could find a diagram of the main board, I could figure out which pin is send and which is receive and I would know for sure.
 
You can safely swap them and see if it works, it just might confuse someone later on. pins 2&3 are tx & rx on db25 and swapped on db9 connectors and you have one other wire that is the ground. Poke the tab in the slot on the front side of the brown connector gently with a scriber and the wire and pin should pull out.
The tinned wire loop on 4&5 is the RTS/CTS handshake loopback saying the machines are not busy. The blue wires link 6,8 and probably 20 which is DSR/DTR loopback plus CD, carrier detect indicating that if there were hardware modems, they are connected. By the look of the wiring, you don't need a null modem adaptor for anything other than swapping tx & rx. However, there needs to be enough wires to carry at least TX,RX,GND,CTS and RTS back to the computer, in case the computer needs to think it is handshaking. You might need to go into the device manager, find the port and look at the properties tab to see what handshaking is turned on at the computer hardware level. Sometimes the software does this, sometimes it expect the port handshake settings to be correctly set.
 
Technocrat,
Today I got the serial tester.

This is with the cable plugged into the laptop.
1696538025284.jpeg

The image below is with the cable plugged into the laptop and the Prototrak Plus.
1696538068753.jpeg


The image below is with the tester plugged into only the Prototrak plus. There are no lights. 1696538124891.jpeg

I tried to send from the prototrak Tape/RS232, 2, 2, -/+ display says ready to send I believe. I press INC or ABS; neither does anything different, no flashing lights. Same with receive, Tape/RS232, 2, 1, -/+, no flashing lights.

I did swap the internal wires around, and the only difference was the TD light turned on, dim red. All testing resulted in the same results. I'm starting to think there is no communication from the main board to the serial port. I know the wires are good; I tested those, but I have no idea if any signal is being sent or received by the main board in the Prototrak.

-IF- that part of the Prototrak is shot and the unit needs to be replaced, what is the most current head unit/display I can change to? Or do my drives demand that I must replace it with an identical Prototrak Plus?

Dan
 
It looks like the prototrack board is not working. I'm not a prototrack expert, so I can't help you there. I do know a lot about serial communication, best bet is that your rs232 driver chip has failed. Sometimes these will be mounted in a socket, other times soldered to the main board. Follow the rx/tx lines onto the circuit board and see which is the chip they connect to.
 
That's what I was afraid of. I'll see what I can see. I doubt there's such a thing as tape to serial connections.

Any idea if I can use a different control like something more modern, or do I have to use the same plus unit with my drives?
 
Today I pulled the board out of the pendent to inspect it. P4 is the RS232 socket; tracing the lines, it looks like they go to this chip. It's soldered in, so if I can find a new chip, I'll have to have my BiL come to swap that out. That falls well outside my area of knowledge.
1696622242916.jpeg

Now, this kind of got my attention and might be the real problem, but I can't say for sure. Not sure if it's connected to the socket, but will have to find out.1696622337253.jpeg
 
Now, this kind of got my attention
You're doing a good job. Looks like that circuit board trace (that used to be there and is now vaporized) is the ground connection for your RS232. One can do a lot of mis-connecting RS232 signals on the connector without damage, but someone found a bad combination that melted that trace. You can check if there is continuity between the connector (blue wire?, pin 7 on the DB-25 connector) and ground on the circuit board (no connection would be bad).

I would re-connect the ground trace (preferably with 30awg wire) and re-evaluate. You still don't really know what caused the fault, so there is risk in that approach, but what do you have to lose? The RS232 spec says current capability of the signal outputs is 0.5 amps, which is enough to melt that trace, so I expect that mistakes were made, a signal was connected to ground, and the circuit board trace was the weakest link. Ground (zero volts) is not a legal logic level in rs232, so I don't think anyone would intentionally do that.

Don't worry about replacing chips until you get that ground re-connected.

This is all my opinion, and if you don't like it, I have others.
 
I just got back in from testing the ground. I was hoping that was it, but nope, the ground is good; I had continuity between both sides of the board and pin 7. Looking close, it kind of looks like someone tried to solder the ground, I wonder if that was because they couldn't get the RS232 to work and just heated up the board too much.

I'm talking to my BiL about this as well as he would do the solder work. But this is the chip I'm looking at. The only thing I see different is the bottom number, 9122 on the one on the board and 1508 on the one on ebay. I'm not sure what that number is in reference to, as I see other chips with different numbers, but I haven't found a 9122. If you have one you suggest, link it and I'll get that one instead of the one I found.

 
The second line is not relevant: date code or some such thing.

My eyes tell me that ground connection is broken, but you can see it a lot better than me.
 
The second line is not relevant: date code or some such thing.

My eyes tell me that ground connection is broken, but you can see it a lot better than me.
I tested the ground between that area and pin 7 and had continuity. Getting close, it looks like someone soldered that area and over heated the board. But I will have my BiL take a close look at it.
Dan
 
that is a very common and tough rs232 driver chip, but they can be blown up. For the pc, you don't really need full RS232 +/- 15V voltage ranges. 0 & 5V will usually work. This gives you a couple of options. This is what I would do, depending on the equipment available. Best option is with an oscilliscope look to see if there is data on pin 10 or 11 of the max232 which is logic level transmitter inputs. It's a dual chip to support rx/tx and handshaking, but only one would be used in this setup. If you got data at the input then you can try a 5V rs232 hack, taking a wire lead from the 5v input and ground to the rx on the pc. Next option would be a quick max232 replacement. Cut the ic off on the top side of the board by cutting close to the body, leaving teh pins soldered into the board. Piggyback a new max232 to the pins and solder it on. Third option is a desolder, remove and replace. good luck!
 
you may need to clip out the max232 before the 5v rs232 attempt because it may be internally shorted, pulling the input data lines low. try 10 & 15 to the computer and 11 & 15 to the computer. If you are using a computer with real serial ports, also try a usb serial adaptor with a prolific pl2303 and no driver chip https://www.waveshare.com/pl2303-usb-uart-board-micro.htm
 
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