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Problems using matlab to connect scope with multiple channels

Question asked by lixiaozhou222 on May 21, 2012
Latest reply on May 22, 2012 by algoss
Dear everyone, 
I am using matlab to connect Agilent 9000X scope, I have two signals connected to CH1 and CH2, respectively.
My purpose is to get data from both 1 and 2 channel using matlab.

When I use the following script to read data from a single channel CH1, it works well.

fprintf(obj1,':DIGITIZE CHANNEL1');
fprintf(obj1,':WAVEFORM:SOURCE CHANNEL1');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
A=binblockread(obj1,'int8'); 

But the problem is, if I change CH1 to CH2, then warning is, ''a time out occured before binblockread.''

fprintf(obj1,':DIGITIZE CHANNEL2');
fprintf(obj1,':WAVEFORM:SOURCE CHANNEL2');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
A=binblockread(obj1,'int8'); 

NOTE that I just read a single channel in the previous 2 cases.
Why does that happen? I just change 'CHANNEL1' to 'CHANNEL2', and nothing else is different.....
Thank you for kind help!

By the way, If I want to read data from CH1 and CH2 the same time, could I run it like this:

fprintf(obj1,':DIGITIZE CHANNEL1');
fprintf(obj1,':WAVEFORM:SOURCE CHANNEL1');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
A=binblockread(obj1,'int8');

fprintf(obj1,':DIGITIZE CHANNEL2');
fprintf(obj1,':WAVEFORM:SOURCE CHANNEL2');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
B=binblockread(obj1,'int8'); 

Or in this way:

fprintf(obj1,':DIGITIZE CHANNEL');

fprintf(obj1,':WAVEFORM:SOURCE CHANNEL1');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
A=binblockread(obj1,'int8');

fprintf(obj1,':WAVEFORM:SOURCE CHANNEL2');
fprintf(obj1,':WAVEFORM:FORMAT BYTE');
fprintf(obj1,':WAVEFORM:DATA?');
B=binblockread(obj1,'int8'); 

In what way can I make sure CH1 and CH2 are read synchronously? 
Well, we still need to solve the 'time out' problem at first.  

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