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what is the serial port protocol??

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haney

New Member
hello,
is it just a simple configuration of the bit rate, parity, stop bit, etc... or is it more then that and is some kind of api (.dll) that needs to be installed on the computer??
how to find out if an external device that is connected to the pc(port rs-232) by someone else is using a specific protocol or not??
 

haney

New Member
thanks for the link but it didn't help me out with my two questions since i don't even know what are the available protocols in hardware comunications. by the way, the link shows how to find out if your device is DTE or DCE but for 25-pin only while most of devices around here are using 9-pin to 9-pin cables.
 

carbonzit

Active Member
by the way, the link shows how to find out if your device is DTE or DCE but for 25-pin only while most of devices around here are using 9-pin to 9-pin cables.

There's a 9- to 25-pin conversion table about a third of the way down the page. You can find the 9-pin "D" pinouts lots of places on the web.
 
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haney

New Member
the 9-pin cable doesn't have "unassigned" and "control" pins for testing! he tested the unassigned(pin 7) with control(pin 2) and transmit(pin 3) however i don't understand how is finding the type of device(DTE or DCE) is going to help me find the exact protocol that is used for communication.
 

Sceadwian

Banned
The RS232C standard does not define a protocol for communication only a basic physical layer with some control signals (that are almost never used modernly) This is NOT a protocol, the answer to your question is very simple; it is completely dependent on the device(s) as far as the software protocol for communication between the devices goes that is outside the scope of the RS232 standard. Basically there is no way to determine it empiracly, you have to know from the data sheet from the devices or decode the protocol yourself.
 

haney

New Member
ok, so how do i find out a list of commands that i can use with a device without finding out what chipset it has or going to manual paper?? i mean is there any general commands or a command that i can use to retrive the list of supported commands for a device??
consider this as a situation that needs exactly what i asked for:
there is a lightpad(a panel that you write on it like the one in college class) in doctor office and he wants me to write a computer program(.NET) that can take a picture of whatever he writes on it. now that device is connected to computer via rs-232 port. he already has a program that converts whatever he writes down to typed text in computer but that program doesn't give me any COM component(.dll) to use for my purpose. so here is my solution:
1- the device is connected via rs-232 and with 9-pin cable so i can easily send any command that i want to but how the heck should i know these factors--> Bit rate, Data bits, Parity, Stop bits, Handshake???
2- how should i find out what commands does it support?? i've access to nothing except the device and i can't open it to see what chipset it has.
 

carbonzit

Active Member
Have you at least tried to communicate with the device using Hyper Terminal (a utility that's available, so far as I know, on every Windoze machine)? You can type commands directly into this program, and see the response from the device (if any). That's kind of the standard way of trying to talk to unknown devices.
 

Pommie

Well-Known Member
Most Helpful Member
You can start with hyperterminal set at 19200, 8, n, 1, no handshaking and send it commands like AT, Ctrl-A to Ctrl-Z ? and ?A to ?Z etc. Better still, if you have a scope then you can check TX or RX and see what the baud rate is and replace the 19200 with the correct number.

However, if you manage to find the command to read the image then you still have to decode it. Not an easy task at all.

Good luck,

Mike.
 

haney

New Member
unfortunatly doc is using win 7 64x which doesn't have hyperterminal since microsoft removed it by some unknown reason! but that's not the problem, i can create a small application to send the commands however there is one sample on msmvps.com which i downloaded but when i send the commands i get no response at all no matter what i sent! the response is always empty. by the way, the guy who created that sample surly knows a lot about port programming. you can understand that from his tutorial. so maybe the device is very customized and/or the firmware is written in a customized way to accept just one or two certain commands. is that possible??
 
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Reloadron

Well-Known Member
Most Helpful Member
Just as a side note the last version of Windows to contain Hyper Terminal was Windows XP. Hyper Terminal was removed from Windows Vista and Windows 7. However, for those wishing to use Hyper Terminal on the latter Windows versions it will run on them (32 or 64 bit). It is just a matter of getting the few files (the hyper terminal .dll file and the hyper terminal .exe file) and placing them in the root of the OS drive on a Windows Vista or Windows 7 system.

I see rthat was covered. :)

there is a lightpad(a panel that you write on it like the one in college class) in doctor office and he wants me to write a computer program(.NET) that can take a picture of whatever he writes on it.

So is all you want is a screen shot image of the open window?

Ron
 

haney

New Member
yah! but i want also to learn the basics otherwise i could have used a lot of mini softwares to capture the screen or part of it. sometimes there is other types of devices connected to pc via ports. so me as a programmer should be able to use them all !!
 

ericgibbs

Well-Known Member
Most Helpful Member
yah! but i want also to learn the basics otherwise i could have used a lot of mini softwares to capture the screen or part of it. sometimes there is other types of devices connected to pc via ports. so me as a programmer should be able to use them all !!

hi,
Which PC programming do you use.?
 
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ericgibbs

Well-Known Member
Most Helpful Member
i'm a .NET programmer mostly c# and vb.net

hi,
I use Visual Basic 5, there are lots of VB source code programs on the web for serial and parallel port communication.

Give us an example of the sort of application you would like to try.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,
Can you explain how the PC is connected to the external device and what the external device is.??

This reply isn't really helpful.
but i don't get any respond at all.
 

carbonzit

Active Member
Can you explain how the PC is connected to the external device and what the external device is.??

Eric, the O.P. did tell us

there is a lightpad(a panel that you write on it like the one in college class) in doctor office and he wants me to write a computer program(.NET) that can take a picture of whatever he writes on it. now that device is connected to computer via rs-232 port.

I'm guessing they probably can't tell us much more than that (although, O.P., it would be helpful if you could tell us more about the device: manufacturer? model?).
 

ericgibbs

Well-Known Member
Most Helpful Member
hi cz,
I am trying to determine what the OP is really asking.

The first post requested RS232 protcols, then available protocols.

Also one post suggests OCR of hand written text on the Tablet to a standard text into a PC screen.
An unknown command set for a unknown device.

hi haney,
Do you have a model number for the Tablet on which the text is hand written.?
I'm sure we can help, but we need more information.:)

I could write a test.exe program for the PC serial port using VB, but I need the model type.
 
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