serial port

[stan58]

I can open a serial port as follows




open "com";(portn);":19200,n,8,1,ds0,cs0,rs" for random as #commwt
. This works and allows the port to be user specified.

portn is a variable selected by the user for the port to be used. My problem is what is the syntax in order to allow the baudrate to be specified by a variable in the same way?

[stan58]

Sorry for another stupid question worked it out
brate=9600
portn= 8

open "com(portn);(brate),n,8,1" for random as #commwt

[stan58]

No that doesn't work after all.
I just want the user to select the port and baud rate and then use that data to open the serial port , at the moment I can use the port number but I cant get the baud rate syntax right.

[Brandon Parker]

You will first need to check to see which COM Ports are actually available to make it clean. There are many things that need to be checked (or be known) for the actual communication to work correctly. You just need to get the concatenation for the COM Port string down correctly to be able to build it.

You can use the "+" operator or the ";" to concatenate the string, but remember that you have to use the str$() function to convert numeric values to strings when you use the "+" operator and this is optional if you use the ";".

Open "Com" + str$(i) + ":" + str$(BaudRate) + ",n,8,1,ds0,cs0,rs0" For random As #COM

See if this will get you started.

Hint... You can use a looping structure to go through all possible COM Port Numbers and use an Array of BaudRates; looping through those as well to get all possible permutations of COM Port Number/ BaudRates.

Hint 2... You can containerize the opening of the COM Port that way you can catch any error and handle it within that container (i.e. function/ subroutine) to make it very clean.

I hope this helps point you in the right direction and continue asking questions if you need to.


{:0)

Brandon R. Parker

[stan58]

Thank you I will try again.

[Rod]

A tip would be to print the command line instead of using the open command . That way you can see the string you have created.

[stan58]

Sorry but struggling with the syntax.
My serial port is working fine if I just put in the baudrate as a number along with the other parameters. My problem is that I want the user to have the ability to set them . So I have a settings window and allow the user to run a check on available com ports and also to manually set the baudrate, this works fine and I then store the data . Before opening the port I get the data into portn and brate variables . Now if I run the example code the port opens fine with the correct port number. My problem Is how do I add the brate variable to the string?


open "com";(portn);":19200,n,8,1,ds0,cs0,rs" for random as #commwt (this works fine, but how do I include the brate variable into the string)
(brate)

[Rod]

This appears to work for me.

portn=3
baud=19200

open "com3:19200,n,8,1,ds0,cs0,rs" for random as #comm
close #comm
print "com";(portn);":";baud;",n,8,1,ds0,cs0,rs"
open "com";(portn);":";baud;",n,8,1,ds0,cs0,rs" for random as #comm
close #comm


[Brandon Parker]

Rod is correct; that should work although I do have to say that the parenthesis around the portn variable are not required. Frankly I'm surprised this doesn't throw an error since the parenthesis are not actually doing anything or part of something; they are just kind of there.... LB doesn't seem to mind them though...

This should work.....
Using str$() with the variables and concatenating using "+" operator.
i = 3
BaudRate = 19200
Print "Com" + str$(i) + ":" + str$(BaudRate) + ",n,8,1,ds0,cs0,rs0"
Open "Com" + str$(i) + ":" + str$(BaudRate) + ",n,8,1,ds0,cs0,rs0" For random As #COM

Not using str$() and using the ";" operator for concatenation.
i = 3
BaudRate = 19200
Print "Com";i;":";BaudRate;",n,8,1,ds0,cs0,rs0"
Open "Com";i;":";BaudRate;",n,8,1,ds0,cs0,rs0" For random As #COM

The two examples provided produce the same output with respect to the concatenated string and should thus be interchangeable.

What error are you getting?


{:0)

Brandon R. Parker

[Rod]

Yes quite right the () are not required. Printing the command string is the fastest way to see your mistakes.

[stan58]

thanks everybody for all your help I will try the suggestions soon. The error would suggest a baudrate error ,I have two error messages in my application main window.if the port can not be opened "oncommerror" i prompt "NO USB DEVICE FITTED" if the serial data string is recieved but does not have the correct terminator then I prompt "COMS" and in the main weight display text box ?. It is the latter prompt that occured.

[stan58]

Dont know where the imogys came from? should of read "??"

[Rod]

Use the ladybug icon and step through your program in the debugger to establish EXACTLY what line of code generates your error.

[stan58]

now I know should have read question marks!

[stan58]

Thanks rod will do and report back