sending and receiving IMAGE using serial port(USB to serial)

Hi friends,

Actually I have an image which need to be transferred via serial port. As my laptop dosent contain serial port i am using USB to serial convertor.I am sending image from one computer other using two USB to serials and null modem. I am doing this for testing purpose and later null modem will be replaced by 8051 controller. I wrote a code for transferring but i am unable to receive data proper control. Please check the below code.

For Transfering

if true

    SendData=serial('COM1','BaudRate',256000);
    fopen(SendData);
    [rows,columns]=size(Encryptedimage);
      for k=1:3
       for i=1:rows
           for j=1:columns
                data=num2str(EncryptedImage(i,j,k));
                fprintf(SendData, '%c' , '*');
                fprintf(SendData, '%s',data);
           end
       end
  end
  fclose(SendData);
  delete(SendData);
  clear SendData;

end

For receiving

if true

recData=serial('COM2','BaudRate',256000);
fopen(recData);
while(1)
            Input1=fread(receiveTemp)

              if(isempty(Input1))
                  continue;
              else
              disp('Value received')
              for k=1:3
                  for i=1:rows
                      for j=1:columns

                              Input1=char(Input1);                  
                              Input1=sscanf(Input1, '%d');
                              EncryptedImage1(i,j,k)=Input1;
                              Input1=fread(receiveTemp);

                          end
                      end
                  end
              end
              if(i==rows & j==columns & k==3)
                  break;
              end
  end

end

Now problem is while receiving Input1 is getting around 120 values at a time. please help me in rectifying this issue.

[gullu]

Hey I am using combination of led and photo diode for transmitting an image through one computer and receive it using another.I tried the code as above using MATLAB as interface.I too am getting the error of dimension mismatch.Did you get where the problem lies?...?

[Walter Roberson]

Did you make the changes as per my Answer ?

[gullu]

yes I tried as per the changes suggested by you.Still the input is receiving lot of pixel values at a time.I want it to receive one value at a time so that the image is recovered at the receiving end.

[Walter Roberson]

As I indicated earlier, fread() will by default keep reading until the buffer is full. You can tell it otherwise by passing a parameter which is the number of elements to read. For example,

fread(fid, 1, 'uint8=>char')

However, if your protocol is '*' followed by a decimal number, then you should be using fscanf()

fscanf(fid, '*%d', 1)

[gullu]

Thanks a lot.

[hina khan]

hello, i am doing the same as gullu and want to transmit an image from the led transmitter and receive it on the photodiode receiver circuit from serial port, i some what changed this code but i am unable to receive any thing. i also want to know what is this "receivetemp" and what is the purpose of giving an if condition at the end? thanks in advance

[dinh nguyen thanh]

can you me funtion EncryptedImage(i,j,k) and EncryptedImage1(i,j,k) thank you

[Walter Roberson]

Those are arrays not functions.

[dinh nguyen thanh]

I want to transmit an image from the led transmitter and receive it on the photodiode receiver circuit from serial port but I have problem with Unexpected Error: The number of bytes written OutputBufferSize (must be less than or equal to OutputBufferSize-BytesToOutput.).

I set OutputBufferSize =1000000, but only send small Image. I want to send and receive one value at a time.

My code :

send:

s=serial('com2');
s.OutputBufferSize=10000000;
s.Timeout=500;
s.BaudRate=115200;
fopen(s);
I = imread('girl.jpg');
b = dec2bin(I);
du = bin2dec(b);
du=(du)';
du=num2str(du);
fprintf(s,du);

receive:

data1 = fscanf(s)
data1=str2num(data1);
data1=(data1)';
I = imread('5.jpg');
data1=reshape(data1,size(I));
imwrite(uint8(data1),'dinh.jpg','jpg');

please help me

[Walter Roberson]

Sending one value at a time:

for K = 1 : numel(I)
  fprintf(s, '%d\n', I(K));
end

this will be slow.

[Priya Dharsini]

Will the above code work to recover the image at the reciever? Even am working with image transmission through LED.

[Walter Roberson]

Which version of "above code" ?

[Shiv]

@ dinh nguyen thanh

why you have used '5.jpg' what image i should read their

[Walter Roberson]

Shiv:

At that point in the code you should read an image that is the exact same size as the original image, but is not the original image.

The imread of 5.jpg there is used only to establish the size of the image. It would be better if the size were just transmitted first, and then the imread() at the destination would not be needed.

[Shiv]

Thank You sir and how can we transmit the just the size.

[Walter Roberson]

 size_bytes = [uint8(ndims(TheImage)), typecast( uint16(size(TheImage)), 'uint8')];

Now transmit the bytes in size_bytes.

Note: if any dimension of the image can be more than 65535 then you need to use uint32 instead of uint16

To reconstruct: read the first byte. That tells you how many dimensions follow. Read that many uint16 . That will give you the size information.

However, looking back I see that you are transmitting in character form, not as binary, so

size_bytes = [ndims(TheImage), size(TheImage)];

and transmit those such as with

   fprintf(s, '%d\n', size_bytes)

[Shiv]

Sir i have used the following code for receiving image from serial port but im not able to reconstruct

receiver code:

s=serial('com1');
s.InputBufferSize=10000000;
s.Timeout=1500;
s.BaudRate=19200;
fopen(s);
data1 = fscanf(s)
data1=str2num(data1);
data1=(data1)';
data1=reshape(data1,[255,255,3]);
imwrite(uint8(data1),'shiv.jpg','jpg');

can you please help me with the code for receiving i need to submit my working project on next week.

Thank You...

[Walter Roberson]

In the transmission, before sending the content, use

img_size = size(TheImage);
fprintf(s, '%d ', img_size);
fprintf(s, '\n');

and then the code to transmit the content of the image:

fprintf(s, '%d ', TheImage);
fprintf(s, '\n');

Then in the receiver, after the fopen(s):

   img_size = fscanf(s, '%d') .';
   data1 = uint8( fscanf(s, '%d') );
   data1 = reshape( data1, img_size );
   imwrite( data1, 'shiv.jpg', 'jpg');

[Shiv]

sir i have tried as you said but while transmitting i got error at

fprintf(s, '\n', img_size(end));
as: Matching failure in format.

so i removed img_size(end) and transmitted

and at receiver side at

data1 = reshape(data1, img_size );

getting error as: To RESHAPE the number of elements must not change.

so what can i do now.?

[Walter Roberson]

Sorry, the img_size(end) was a typo, and you were right to remove it.

On the transmitting side, please show

img_size

and also please show how you send your image.

On the receiving end, please show

img_size
size(data1)

[Shiv]

Sir this is the code im using for transmission

s=serial('com4');

s.OutputBufferSize=10000000;

s.Timeout=600;

s.BaudRate=19200;

I = imread('images.jpg');

fopen(s);

img_size = size(I);

fprintf(s, '%d ', img_size);

fprintf(s, '\n');

b = dec2bin(I);

du = bin2dec(b);

du=(du)';

fprintf(s,'%d ', du);

fprintf(s, '\n');

fclose(s);

and the receiver code:

s=serial('com3');

s.InputBufferSize=10000000;

s.Timeout=600;

s.BaudRate=19200;

fopen(s);

img_size = fscanf(s, '%d') .';

data1 = uint8( fscanf(s, '%d') )

data1=(data1)';

data1 = reshape( data1, img_size );

imwrite(data1, 'shiv.jpg', 'jpg');

fclose(s);

[Shiv]

This is how im trying send and receive the image.

Thank You..

[Walter Roberson]

On the transmitting side, the lines

b = dec2bin(I);

du = bin2dec(b);

du=(du)';

fprintf(s,'%d ', du);

can be replaced by

fprintf(s, '%d ', I);

On the receiving side, you can leave out

data1=(data1)';

Both of these sets of changes are just for cleaner more efficient code, and do not affect what would be sent or received.

There is no obvious reason why the sent image size would not equal the received image size.

In the sending side, disp(img_size) and the same in the receiver, and tell us what shows up.

[Shiv]

Sir for disp(img_size) i got [115 115 3] in both transmission and receiver side. But im not getting any data at receiver i.e, data1 = [] there is no data in data1. I think the error is due to new line at

fprintf(s, '%d ', img_size);
fprintf(s, '\n');

the data is not reading by receiver after the new line.

and is there any other way to make serial data into matrix instead of using Reshape..?

[Walter Roberson]

"is there any other way to make serial data into matrix instead of using Reshape..?"

Yes. Replace

data1 = uint8( fscanf(s, '%d') );

with

data1 = uint8( fscanf(s, '%d', img_size) )

Are you getting a message about time-outs?

You would not be able to successfully read the img_size as [115 115 3] if the newline was not there and functioning properly; we can now be sure that part is working.

The sending side should be

s = serial('com4');
s.OutputBufferSize = 10000000;
s.Timeout = 600;
s.BaudRate = 19200;
fopen(s);

I = imread('images.jpg');
img_size = size(I);

fprintf(s, '%d ', img_size);
fprintf(s, '\n');
fprintf(s, '%d ', I);
fprintf(s, '\n');

fclose(s);

[Shiv]

There is no time-out error. And still im not able able to read the data after new line.

fprintf(s, '%d ', img_size); fprintf(s, '\n');

after execution the data1 = [] not getting any data.

and for fprintf(s, '%d ', I); it gives error as 'The third input argument must be a string.' so i have used I = dec2bin(I); I = bin2dec(I); before fprintf(s, '%d ', I)

[Walter Roberson]

Change

fprintf(s, '%d ', I);

to

fprintf(s, '%d ', double(I(:)));

See https://www.mathworks.com/matlabcentral/answers/214786-serial-fprintf-of-non-string for more on that.

On the receiving side, try

while true
  data1 = uint8( fscanf(s, '%d') );
  if ~isempty(data1); break; end
end
data1 = reshape(dat1, img_size);

Though, if I were programming the code, I would not be trying to fprintf() everything at one time: I would presume that trying to do so would overflow the output buffer. I would transmit at most one column at a time.

[Shiv]

Thank You sir finally i am able to reconstruct the image. But now the only problem is that after transmitting the image i need to wait till time-out to occur to get the output, so how can i get output before time-out that is immediately after transmission.

[Walter Roberson]

If you are having to wait for timeout then the \n of the sending system is not being recognized. Did you accidentally leave out the fprintfs(, '\n') after the fprintf(s, '%d ', double(I(:))); ?

[Shiv]

Im sending fprintf(s, '\n') after fprintf(s, '%d ', double(I(:))); but im losing few data while receiving, so what can i do to compensate the lost data?

[Walter Roberson]

Do not send as much data at one time before the \n .

Make sure that both devices have hardware flow control turned on.

https://www.mathworks.com/help/matlab/matlab_external/flowcontrol.html

https://www.mathworks.com/help/instrument/flowcontrol.html

[Priya Dharsini]

AM planning to send a biomedical image through LED.SO what image processing to be done for a biomedical image?

[Walter Roberson]

Use several steps:

1. read the biomedical image in, which is a step that is independent of any image processing you plan to do
2. Do whatever image processing is appropriate for your biomedical image for whatever purpose you need, which is a step that is independent of reading the image and is independent of any plans to transmit the image
3. if the processed image is not already uint8, use typecast() to make a byte stream out of it. This is a step that is independent of reading the image and is independent of whatever image processing you did.
4. reshape your now uint8 image to a vector
5. transmit the uint8 vector by LED technology -- which is a step that is independent of everything having to do with calculating which uint8 are going to be transmitted

[Priya Dharsini]

Thank you

Answer 1

[Walter Roberson]

Replace

[rows,columns]=size(Encryptedimage);

with

[rows,columns,bands]=size(Encryptedimage);

In the form of size() that you were using, "columns" would be set to the real columns times the number of bands.

[srikanth]

Thanks for correcting me. But still this didnt rectified my problem of serial communication. When i am transferring values to hyper terminal i can see values continuously. But when using Matlab at reception side 'Input1' variable is showing lots of values at a time and matlab is giving error dimension mismatch. Maybe i feel there is some synchronization problem between transition and reception.How to rectify this issue?

[Walter Roberson]

You know that fread() without a size parameter will try to read until the buffer is full ? http://www.mathworks.com/help/matlab/ref/serial.fread.html

You should also be considering using the 'precision' parameter of fread().

You might want to re-think why it is that you are using the formatted-data function fprintf() to send the data, but are using the binary-data function fread() to read it.