Timeout problem in matlab

Hi,

I am trying to read data through serial communication in matlab

I am reading 2 bytes of data

First byte is zero for most of the times and 2nd byte contains information.

I am getting timeout error Is there any command to read data starting with zeros Warning: Unsuccessful read: A timeout occurred.

Code:
  nexys = serial('COM1', 'BaudRate', 9600, 'Parity', 'odd', 'Terminator', '', 'Timeout', 1);
  fopen(nexys);
  myNum = 4563;
  %fprintf(nexys, 'd1539'); %Fungerar
  %fprintf(nexys, 'd%4d', myNum); %Fungerar
  for i=1:2
      fprintf(nexys, 's');
      scan_s1 = fscanf(nexys,'%s')-0;
      fprintf(nexys, 't');
      scan_s2 = fscanf(nexys,'%s')-0;
  end

Can anybody suggest something about this

Thanks Jim

[Matt Kindig]

On what line is the timeout error thrown? Have you verified that the scan_s1 and scan_s2 are incorrect?

It looks like you are setting the 'Terminator' to empty. In my experience, a timeout error can arise when the device does not send a specified terminator string that Matlab recognizes. I'm not sure how it would respond with an empty terminator specified.

[Jim]

Hi Matt kindig,

Thanks for ur reply. Even when I am using LF as terminator I am getting the same error: Yes, I think matlab does not recognizes the data I am sending Is this because 1st byte contains 00000000? Is there any command to recognize zeros in matlab

Thanks in advance

Answer 1

[Jan]

You try to read a string but do not define a terminator. Even the the LF terminator, the string might not be terminated, when no LF appears in the data stream. So are you sure, that FSCANF for a string is what you want?

FREAD read all values, while the import of a string might be impeded by a zero byte, because they terminate strings in C.

[Jim]

Hi Jan,

Thanks for your reply. In the command fscanf

scan_s1 = fscanf(nexys,'%s')-0;

What does "-0" will do exactly?

What is the need of substracting 0 from a string

Thanks Jim

[Jan]

@Jim: Subtracting 0 from a CHAR array converts the type to DOUBLE:

c = '123'
d = c + 0
class(d)

Alternative, which is less funky:

d = double(c);