Making a RS232 hub.

[madsovenielsen]

I lost everything I typed.

Your system is well defined. Ports, baud rate etc. You need to know what signals you need to support: DTR, DSR, CTS, RTS, TxD, Rxd, SG and/or RI (Ring Indicator)

The MAX232 is a well know chip for interfacing RS232 to TTL levels. Start there.

You might be able to directly tri-state the I/O pins or add your own tri-state buffer or use data selectors/multiplexor chips to select which port.

3 bits will do seven ports, 4 bits can select them one at a time.

Now, the question is "How do you envision how your going to select which computer is connected."?

Ideally i would like not to select what computer to communicate with on the hardware e.g. dip switch etc.

But i realize that a "software" solution programmed into a MC on the board is a rather complex way to go for a total DIY electronics newbie.

What do you think ?

Kind regards Mads Nielsen

 

[KeepItSimpleStupid]

It might not be too bad if you pick your processor carefully. There are a couple of BASIC programmable uC that could be used if your up for it. I'll have to see if they can handle 2 serial ports. An in and an out.

What I think you would have to do is to implement basically a modem escape sequence and a small command decoder. You would basically try to detect silence (> x sec) "+++" (>x sec), then it would break into a monitor which might say "Connect to port (1-4)" and reply with "Connecting to Port n"

You did say, "You wanted to make one", right?

 

[madsovenielsen]

It might not be too bad if you pick your processor carefully. There are a couple of BASIC programmable uC that could be used if your up for it. I'll have to see if they can handle 2 serial ports. An in and an out.

What I think you would have to do is to implement basically a modem escape sequence and a small command decoder. You would basically try to detect silence (> x sec) "+++" (>x sec), then it would break into a monitor which might say "Connect to port (1-4)" and reply with "Connecting to Port n"

You did say, "You wanted to make one", right?

Yes i want to make one my self.

But i have no idea where to start and what components to use.

Kind regards Mads Nielsen

 

[KeepItSimpleStupid]

OK max:

Take a look at the following datasheet for the MAX232 **broken link removed** and see if anything makes sense to you.


And also take a look at this: **broken link removed**

This would be the basis of the design.

A tri-state inverter or buffer and another part is necessary too, to "glue" this together.

These uC's https://cubloc.com/product/01_01.php are programmable in BASIC and Ladder Logic. Most have 2 serial ports and one has 4 serial ports and a real-time clock (RTC). The RTC could prove useful for your project. The main website is www.comfiletech.com .

i
I did not evaluate the suitability of the language. The

 

[madsovenielsen]

OK max:

Take a look at the following datasheet for the MAX232 **broken link removed** and see if anything makes sense to you.


And also take a look at this: **broken link removed**

This would be the basis of the design.

A tri-state inverter or buffer and another part is necessary too, to "glue" this together.

These uC's Comfile Technology Inc. are programmable in BASIC and Ladder Logic. Most have 2 serial ports and one has 4 serial ports and a real-time clock (RTC). The RTC could prove useful for your project. The main website is Welcome to Comfile Technology, Creator of Industrial Innovations .

i
I did not evaluate the suitability of the language. The

That makes perfect sense. I have to use some sort of buffer to control what machine i am communicating with, in other words how the DB9 ports are "connected"

Things are starting to fall into place

 

[KeepItSimpleStupid]

Not a buffer. Electrically you can enable what device you want to communicate with with a digital port. The switching needs to be done electrically. The electronics need to be able to switch the ports. 1 in to 5 out.

The uC sits between your console and the input to the electronics

It "inspects" the character stream for silence. If there is a "second" of silence, it looks for a "+++". If it senses another second of silence", then it breaks into the selection routine.

You could have a 5 character buffer or so to "trap" the +++.

You may need to implement software flow control. ^S and ^Q with resume on character.

 

[madsovenielsen]

Not a buffer. Electrically you can enable what device you want to communicate with with a digital port. The switching needs to be done electrically. The electronics need to be able to switch the ports. 1 in to 5 out.

The uC sits between your console and the input to the electronics

It "inspects" the character stream for silence. If there is a "second" of silence, it looks for a "+++". If it senses another second of silence", then it breaks into the selection routine.

You could have a 5 character buffer or so to "trap" the +++.

You may need to implement software flow control. ^S and ^Q with resume on character.

I have found this: Making a RS232 hub

Afther reading the description of the board, i think that this is maybe something i can use as a basis ?

I am familiar with C programming so the actual code is not an issue.

 

[KeepItSimpleStupid]

Very bizzare. The author doesn't do a good job explaining things. I do believe he is using two serial ports. One for control and one for out. He is physically controlling power to the devices which is not something you wanted to do. You also wanted to use a single serial port.

PICS will require a development kit which will increase the cost.

If your willing to use two serial ports, then it could work except you have to create better hardware like I suggested.

I do think you could just pass the wait "+++" wait for generation 1.

 

[3v0]

What KeepItSimpleStupid says is correct if you are not interested in micro controller programing. On the other hand if it is something you want to play with the programmer is tool purchase and well worth the $35 or whatever.

Many times it is cheaper to use a micro controller based design.