GPIB RS232 speed comparison

[siva0182]

Hi all

I am not sure if this is the right board to post my question.I am not sure if the problem I am facing is a software issue or a hardware issue.

I am using agilent 34970A data logger   and 34901a(normal DAQ card) and 34907a (multifunction Actuator card capable of supplying a voltage signal).

I have used a NI GPIB/Rs232  to connect my data logger to Computer.

 http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=968 i am using the sl no 2 in this link as a driver to communicate with the agilent datalogger.

I read data ,process and send an output voltage through 34907a card.

I have done this using Rs232 and then using GPIb card. But the speeds are same in both the cases.

I was expecting higher speeds but both have same speeds(to complete one loop of read process and write it takes about 300 millisecs).

The instrument read write and scan time specs are  much lower..

So I am not sure where the speed is lost..

Is it because  i am using a common driver for both GPIB and Rs232..is there any faster way of communicating using direct serial communication  vi's or so?

your help is highly appreciated.

thanks

regards

Siva

[JK1]

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In RS 232 protocol the transfer speed depends on the baud rate settings and in case of GPIB it is 1MB/s or depends upon the GPIB version.  These speeds are governed by the physical (electronics) layer and software (instrument/device drivers) does not interfere with it.  Software does the job of passing the data to and from the physical layer FIFO's and its a interface between the software and the hardware layer.

When we take the physical layer into consideration, speed may decrease due to bus load (number of devices in the bus), too many handshaking between devices, distance between the devices and i hope that above parameters are not be out of its numbers in your application.

Other counter part is the device driver that is being employed for communication with the hardware. Check even if simple read/Write (no other activities should be done) consumes same time.  You might use a hyper terminal to see if the device is constantly sending/receving some handshaking signals that increase the bus load.

[siva0182]

My device and computer are closer to each other and i use the normal lengths of GPIB and Rs232 cable.

There are  not many devices  .

I am reading from one card and writing to another card in the same instrument.

I tried a simple read(single reading) and (single )write   commans without any adition processing and it takes 160 millisecs still slower than expected I wanted to do such a thing in about 30 millisecs  as the specs of instrument and GPIB allow such rates.

[JK1]

Try employing a NI-Spy to see if there are any constant data being sent or handshaking signals exchanged.  If there is an option to minimize these handshaking signals then the communication should improve.