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RS232:VT100, Data look equivalent but doesn't work

Posted on 1998-12-08
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Last Modified: 2011-10-03
We are programming in Delphi a Programm with a Component we've downloaded.
We wan't to control 'System One' a system to play with a Model Railroad. This System can be controlled with Serial connection to the PC with the VT100 standard.
Problem: when we use the Hyperterminal (Win95) we send a String like this
s c05 s0 80 85 ef
-->when we strike the 'Enter' Key, System One take the data. When we use our Delphi-program it doesn't works. We connected to PC's together to look what our program Send - and the both strings looks equivalent!! but our doesn't works.
So we connected our cable with a Oscilloscope and we detected first the signal with the Hyperterminal --> it sends something, then with our software --> it sends nothing. But when we connect to PC's once again it seams that both send the same chars.
Can anybody help us?
P.S. our test with the Hyperterminal and our software we made on the same System on the Same PC during the same session, and we changed between the to software more than one time. We also didn't forget to disconnect Hyperterminal and our software before work with the other software

(sorry my bad english)
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Question by:zulliger
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  • +2
16 Comments
 
LVL 12

Expert Comment

by:Otta
ID: 1130626
Are you sending 7-bits or 8-bits?
Are you sending a "start" bit?
Are you sending "even", "odd", "mark", "space", or "no" parity?
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Author Comment

by:zulliger
ID: 1130627
8-Bit
9600bps
Parity: none
stopbit: 1
protokol: no


0
 

Author Comment

by:zulliger
ID: 1130628
8-Bit
9600bps
Parity: none
stopbit: 1
protokol: no


0
 

Author Comment

by:zulliger
ID: 1130629
8-Bit
9600bps
Parity: none
stopbit: 1
protokol: no


0
 

Author Comment

by:zulliger
ID: 1130630
8-Bit
9600bps
Parity: none
stopbit: 1
protokol: no


0
 

Author Comment

by:zulliger
ID: 1130631
8-Bit
9600bps
Parity: none
stopbit: 1
protokol: no


0
 
LVL 3

Expert Comment

by:vikiing
ID: 1130632
You're saying "VT100 standard". VT100 is a video terminal from DEC (Digital Equipement Corp.); ¿What is the relation between your project and that terminal?

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Author Comment

by:zulliger
ID: 1130633
I don't know - the Manual of 'System One' describes that we have to use the VT100 terminal emulation

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Expert Comment

by:vikiing
ID: 1130634
Please, ¿could you post the piece of code that works with serial port?.

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LVL 8

Expert Comment

by:netmage
ID: 1130635
Check to see that chr(13) carriage return is being interpreted equally between both programs and not just "white space" omitted or filtered.

netmage
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LVL 12

Expert Comment

by:Otta
ID: 1130636
> You're saying "VT100 standard".
> VT100 is a video terminal from DEC (Digital Equipment Corp.);
> What is the relation between your project and that terminal?

The set of "commands" accepted by that terminal have
outlasted the hardware, and have become a "de facto" standard
for interfaces.  When you use the 'TELNET' command,
part of the TCP/IP protocol, to connect to a UNIX system,
the TELNET-client usually tells UNIX that it is capable
of "emulating" a VT-100 terminal.

The VT-100 command-set can move the cursor to a specific location,
cause all following output to be "inverse-video",
and much more.


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Accepted Solution

by:
adrianwatkins earned 100 total points
ID: 1130637
It will be one of two things that differ between the test with two pc's and the osciliscope.

1. when you hit enter on hyperterminal it sends a C/R and a L/F does your software do the same thing or is it only sending l/f or only sending c/r.

2. IF the data looks the same when you connect two PC's together but does not work when you connect to your unit then we have to ask what is the other pc providing??? I would imagine it is providing Flow control - or more particularly HARDWARE flow control. if your software module is looking for hardware flow control it will not send anything until it sees the correct leads go high/low. if you were connecting the pc's together with null modem lead this cross connects the hardware control leads. what you need to do is create a special plug that loops back the hardware leads. This would look like :

(PC End) 25 Way                         25 Way (Controller End)

2  (TX DATA)   ----------------------------   2  (TX DATA)
3  (RX DATA)   ----------------------------   3

4  (RTS)-------xx                    xx----   4
5  (CTS)-------xx                    xx----   5

6  (DSR)-------xx                    xx----   6
8  (DCD)-------xx                    xx----   8
20 (DTR)-------xx                    xx----   20

7   (SG)-----------------------------------  7

ie on both ends connect shorted pins 4 to 5 and pins 6,8,20. This assumes that the controler is a DCE otherwise you need to connect 2---3 and 3---2

Hope this helps
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Expert Comment

by:vikiing
ID: 1130638
Otta: I know what the VT-100 protocole is (I've started to work with it just when it was born, at 1979, and during 11 years); I just only asked Zulliger what had his project in common with a VT-100 because I don't see the link between a video terminal and a model railroad.
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Author Comment

by:zulliger
ID: 1130639
Thank you very much -> it works. I only made a shortcut between the pins described.
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LVL 12

Expert Comment

by:Otta
ID: 1130640
> I know what the VT-100 protocole [sic]
> is (I've started to work with it just when
> it was born, at 1979, and during 11 years).

I have been a computer-professional since the early 1970's,
long before DEC's VT-100 protocol.  :-)
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Expert Comment

by:vikiing
ID: 1130641
Glad of you, dear Otta.

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