How to receive UDP packets in matlab?

I'm trying to get IMU sensor data from my android phone (from this app) The app Can anyone tell me the best way I can accomplish this?

Thank you.

Answer 1

[Geoff Hayes]

That's a neat little app. If you have the Instrument Control Toolbox, you could probably use the UDP object to get the information that you need.

I don't have that software, so went to the File Exchange and grabbed the Simple UDP Communications App code. It is just one function, judp, that allows you to send and receive UDP packets.

Assuming that the Wireless IMU app is running and that I just want to get the next 100 packets, then the following code would do the trick

 % target port as set in the app
 port        = 5555;
 payloadData = cell(100,1);

 for k=1:100

   % get the message/payload only assuming a max size of 200 bytes
   [msg,~] = judp('RECEIVE',port,200);

   % save the payload to the array
   payloadData{k} = msg;

   % convert the message to ASCII and print it out
   fprintf('%s\n',char(msg)');

 end

Some sample payload data was

 1406156316.20970, 3,   0.157,  0.333,  9.850, 4,  -0.000,  0.001, -0.000, 5,    
    14.699,-0.420,-49.500
 1406156316.27678, 3,   0.271,  0.287,  9.832
 1406156316.34447, 3,   0.199,  0.281,  9.844
 1406156316.41106, 3,   0.201,  0.286,  9.844, 4,  -0.001,  0.001,  0.001, 5,  
    14.699,-0.479,-49.680
 1406156316.47826, 3,   0.242,  0.319,  9.856
 1406156316.54561, 3,   0.208,  0.283,  9.861
 1406156316.61258, 3,   0.216,  0.250,  9.862, 4,   0.000,  0.000, -0.000, 5,  
    14.699,-0.420,-49.860

As described in the Wireless IMU app, a comma separated list of data is sent in the UDP payload. I found that the payload sizes were either 44 bytes or 100 bytes. The smaller payloads contained a timestamp and the accelerometer data only, whereas the larger messages had the timestamp, accelerometer, gyroscope and magnetometer data. Two of the former appeared for one of the latter at the Slow (Normal) update rate.

All data seemed to match that which was displayed in the app on my phone.

Try the above and see what happens!

[HJ Jay]

Hello Geoff,

Sorry for the late response. Thank you for your answer, it works perfectly. I had contacted the app developer and it appears he too has used the same function to get his data on matlab.

[Geoff Hayes]

Awesome!

[taher azim]

hey, i was also using the above code but it gave me error stating that Error using judp (line 166) judp.m--Failed to receive UDP packet; connection timed out.

Error in Untitled (line 8) [msg,~] = judp('RECEIVE',port,200);

how to get rid of that error..

% target port as set in the app port = 5555; payloadData = cell(100,1);

 for k=1:100

   % get the message/payload only assuming a max size of 200 bytes
   [msg,~] = judp('RECEIVE',port,200);

   % save the payload to the array
   payloadData{k} = msg;

   % convert the message to ASCII and print it out
   fprintf('%s\n',char(msg)');

 end

Answer 2

[Eddy H]

This solution works for me, but has anyone got this working using the Instrument Control Toolbox? I can't get it to work this way.

echoudp('on',5555)
u = udp('PHONEIP',5555);
fopen(u)
A = fread(u,200)

ERROR: Warning: Unsuccessful read: The specified amount of data was not returned within the Timeout period.