Open a serial terminal in both machines and make sure you can transmit and receive on both sides.

gdjacobs wrote:

Open a serial terminal in both machines and make sure you can transmit and receive on both sides.

On my lte 5300 HyperTerminal cant open the serial port, any hints?
On the other pc it is ok(HyperTerminal can wait for call)
Btw the cable is following this schematic

I triple checked the pinout of the cable and it is correct.
I will test wit another computer aswell
Edit: tested with another laptop and the cable itself is working perfectly, the problem seems my LTE5300 laptop

.legaCy wrote:

On my lte 5300 HyperTerminal cant open the serial port, any hints?
On the other pc it is ok(HyperTerminal can wait for call)

If you run with software based or no flow control, all you need is RX and TX criss-crossed along with a ground pin. Anyway, you need to get that serial port working to do diagnostics.

I'm guessing it's built in to the motherboard? It's enabled in firmware?

gdjacobs wrote:

.legaCy wrote:

On my lte 5300 HyperTerminal cant open the serial port, any hints?
On the other pc it is ok(HyperTerminal can wait for call)

If you run with software based or no flow control, all you need is RX and TX criss-crossed along with a ground pin. Anyway, you need to get that serial port working to do diagnostics.

I'm guessing it's built in to the motherboard? It's enabled in firmware?

Well its the serial port built in the laptop, it seems to be enabled on setup.
Maybe something already using the com port is messing up ?

Possibly. It looks fine in device manager? Maybe the attempted serial network connection is still locking the port?

gdjacobs wrote:

Possibly. It looks fine in device manager? Maybe the attempted serial network connection is still locking the port?

It looks fine on device manager.
Im using HyperTerminal on both machines and i managed to send some small text file.
After that it stopped.

Which port is locking? If you jumper RX and TX on each port and set them for no flow control, which COM port gives you an echo of what you type in hyperterminal?

gdjacobs wrote:

Which port is locking? If you jumper RX and TX on each port and set them for no flow control, which COM port gives you an echo of what you type in hyperterminal?

Both sides when the RX and TX lines are jumpered and the flow control is None have echos in HyperTerminal, but when i connect both computer with the same serial cable and run hyperterminal my LTE cant open the COM port

Something freaky deaky is going on. I'd be wanting to test straight from DOS just to eliminate any OS complications.

gdjacobs wrote:

Something freaky deaky is going on. I'd be wanting to test straight from DOS just to eliminate any OS complications.

Yup that's what i thought, well, i will get one CF-IDE 44 pin adapter soon and will instal windows 95 with bootgui = 0 parameter so it will be easy to transfer drivers for cardbus ethernet card at the first instance so later on i can transfer by SMB over ethernet.
BTW i had similar issues on some customers with RS232 POS Printers, i solved reinstalling Windows, and that is what i will do when the adapter arrive.
But anyway thank you very much for the attention and help 😀

The cable wiring is correct. The only thing that might cause issues is the fact that you used twisted pair cable, which is optimal for differential signals, but not for single-ended signals.

When there is a pulse of signal on one wire of the pair, the other wire of the pair will have a some sort of smallish pulse as well, as the wires within a pair have both magnetic and capacitive coupling between them.

So if you wired both TX and RX wires on same pair, they might disturb each other. Wiring TX and some handshake signal causes less disturbance as handshake signals are not switched so often. If using twisted pair for single ended signals, it is usually best to wire ground as one signal in each pair.

Having said that, for a mere 2m of RS232 signaling which is slew rate limited, the twisted pair wiring should work, but if it does not then try different cable than twisted pair.

If you jumper Rx and Tx so you have loopback through the cable, you can open a terminal, make sure you have echo, and eliminate cable cross-talk as a possibility.

gdjacobs wrote:

If you jumper Rx and Tx so you have loopback through the cable, you can open a terminal, make sure you have echo, and eliminate cable cross-talk as a possibility.

It works i have echo.

Jepael wrote:

The cable wiring is correct. The only thing that might cause issues is the fact that you used twisted pair cable, which is optim […]
Show full quote

The cable wiring is correct. The only thing that might cause issues is the fact that you used twisted pair cable, which is optimal for differential signals, but not for single-ended signals.

When there is a pulse of signal on one wire of the pair, the other wire of the pair will have a some sort of smallish pulse as well, as the wires within a pair have both magnetic and capacitive coupling between them.

So if you wired both TX and RX wires on same pair, they might disturb each other. Wiring TX and some handshake signal causes less disturbance as handshake signals are not switched so often. If using twisted pair for single ended signals, it is usually best to wire ground as one signal in each pair.

Having said that, for a mere 2m of RS232 signaling which is slew rate limited, the twisted pair wiring should work, but if it does not then try different cable than twisted pair.

If i use it with another computer the cable works flawlessly.

Can you make a crossover cable with Rx, Tx, and Gnd?

Try sending in simplex mode. It's half as fast, but less chance of signal crossing.

gdjacobs wrote:

Can you make a crossover cable with Rx, Tx, and Gnd?

this was my first version of the cable and i wasnt even using a utp cable and didn't worked, after all i solved this reinstalling windows .

Be interesting to know which driver was grabbing the port.

Also, three wire serial requires flow control either disabled, or run via software (XON/XOFF).

oldpcguy wrote:

Try sending in simplex mode. It's half as fast, but less chance of signal crossing.

That's right. From a personal experience, a simple serial connection should work no problem for a disctance across approximate 20 meters, though.
As far as I remember, for DOS, there's also a free version of FileMaven. It supports different kinds of serial/parallel connections.
Including the popular 3-wire version that classic programs like Ultrafast Filetransfer Operation used.
If everything fails, I highly suggest to try a serial connection in pure DOS also.
Windows does all sorts of probing (searching for serial mice, modems, etc)

Jo22 wrote:

That's right. From a personal experience, a simple serial connection should work no problem for a disctance across approximate 2 […]
Show full quote

oldpcguy wrote:

Try sending in simplex mode. It's half as fast, but less chance of signal crossing.

That's right. From a personal experience, a simple serial connection should work no problem for a disctance across approximate 20 meters, though.
As far as I remember, for DOS, there's also a free version of FileMaven. It supports different kinds of serial/parallel connections.
Including the popular 3-wire version that classic programs like Ultrafast Filetransfer Operation used.
If everything fails, I highly suggest to try a serial connection in pure DOS also.
Windows does all sorts of probing (searching for serial mice, modems, etc)

I already solved it, with the CF as HD i installed ms-dos and the serial connection with my cable works, but it is not needed anymore cause i can take the CF card and transfer files way faster plugging it into a USB CF card reader.