HTBasic for receiving data from a RS232 device - serial-port

Question

I am not coding neither understand much about it, although have to run an experiment in the laboratory, and have to use HTBasic to receive data from 2 GPIB devices (IEE 488) and one RS232 (this one is a high precision lab scale ).
I am changing/adding to an old script that someone else wrote. It was only to receive data from the 2 GPIB devices.
I must get data only every 15-30 minutes (the experiment will run for a month) and even though I successfully receive data from the lab scale (device interface select code = 12) they only arrive "synchronous" for a loop every e.g. 10ms (milliseconds). If I make it every 1 second the data are "old" e.g. I removed the item from the scale and instead of showing me ZERO "0" it still shows the weight. Imagine what if I ask for a loop every 15 minutes.
It seems that received data arrives in order one by one and displayed with that order. Probably there is an internal buffer or something that stores them. Does any one know how to OPEN and CLOSE the communication with a serial device on DEMAND? e.g. for GPIB devices I am sending a command like TALK (talk) and UNT (untalk) every time the loop takes place, but I can't find out how to do this with the serial device.
I tried the CONTROL 12,100;0 and CONTROL 12,100;1 (XOFF/XON) but it didn't work.
Here is one of the scripts I tried that gives me the correct weighting values, but for loops every 0.01 seconds.
LOOP
ENTER 12 USING "10D";W
PRINT TABXY(70,20),"wEIGHT IS:";W
WAIT 0.01
END LOOP
END

Answer 1

I would suggest trying using handshake control.
You can control the Serial Interface using the HTBASIC CONTROL statement.
For example, you can turn:
CONTROL 9,5;0 ! use DTR and RTS
CONTROL 9,12;0 ! read DSR, CD, and CTS
You should also use Interface handles as such:
ASSIGN #Serial TO 9 ! Opens the Serial Port, and clears buffer
ASSIGN #Serial TO * ! Closes the Serial Port

Answer 2

This should work for 15 Min Cycle (900 Sec):
ON CYCLE 900 GOSUB Get_Serial
LOOP
END LOOP
STOP
Get_serial:!
ASSIGN #Serial TO 12
ENTER #Serial USING "10D";W
RETURN
END

Answer 3

Hi guys and thanks for your answers (they came a bit late though).
Most probably both of your suggestions may work (havent try them ..maybe in the near future)
What I did those days to solve my problem , was basicly something like : LOOP continuusly and print on specific area of the screen (CRT) the serial device values (weight in gramms) , ONDELAY of specific time (eg every 15minutes) go to NEW LOOP (called it LOOOP in the code) which tells program to grab the value of RS232 labscale from the screen (not the device directly) and ofcourse the 2 GPIB devices, and after that repeat the continuus LOOP to show on CRT screen the real/continuus labscale values to prevent bufffer from being full ... and so everything worked smoothly..
I understand that this in not a GOOD way for coding, but as i said i am a rookie in this field ...BUT IT WORKED
So the code i wrote was something like:
[....]
33 ASSIGN #Scale TO 12
52 ENTER #Scale USING "10D";Weight
54 PRINT TABXY(70,20),"Captured LabScaLE Weight=";Weight;" g"
55 A=Weight
90 ON DELAY T GOTO Loooop
92 LOOP
93 ENTER #Scale USING "10D";A
94 A=A
95 PRINT TABXY(65,35);A;TABXY(65,35);
96 !
97 END LOOP
98 !
99 Loooop: GOTO 100 !GRAPSE THN GRAMMH PU AKOLOYTHEI PX 171
100 !
101 !
102 ENTER CRT;A
116 !==============================================START LISTENING FROM RS232 labscale (DISPAY ON CRT CONTINUUS DATA)======
117 !ENTER CRT;Weight
118 Weight=A
119 PRINT TABXY(70,20),"Captured LabScaLE Weight=";Weight;" g"
120 !
121 !==============================================START LISTENING FROM GDS CTRL=======
122 SEND 9;UNL UNT MLA TALK 14 DATA CHR$(255)
123 ENTER 9 USING "#,B,4D,6D";S,Pressurea,Volumea
124 SEND 9;UNT DATA CHR$(255)
128 !=============================================START LISTENING FROM GDS CTRL=======
129 !
130 SEND 8;UNL UNT MLA TALK 13 DATA CHR$(255)
131 ENTER 8 USING "#,B,4D,6D";S,Pressureb,Volumeb
132 SEND 8;UNT DATA CHR$(255)
[.....]
150 GOTO 92 !