how to let pic communicate with matlab

Replies

• 

  wassup

  I will assume your filter is constant. (Does it change/adaptive ? Hope Not)
  Here is what you can do. To use the filter you need impulse response of the filter. Get it from Matlab.
  The array you get will be in floating point ! Convert that into fixed point. (Read more on fixed point arithmetic) Now once you get the h[n], you will have to implement a convolution algo in PIC.
  Now all I can say is PIC is not built for these kind of algorithms !!!!! You will have to use dsPIC.
  
  Give me your filter design, I will try to get something out of it. But you will have change you microcontroller !!!!
• 

  kaibin

  Hi, the band-stop filter is Butterworth type. And yeah, it's constant.
  The band-stop filter needs to filter two peak values, so two butterworth filters with different parameters are needed.
  
  
  [b,a] = butter(n, wn, ‘ftype’, ‘s’)
  
  where n is the filter order, wn = [w1 w2] is the cutoff frequencies
  
  wn=[90 110]
  wn =
  
  90 110
  
  The results:
  >> [b,a]=butter(3,wn,'stop','s')
  b =
  1.0e+011 *
  0.0000 0 0.0000 0 0.0029 0 9.7030
  a =
  1.0e+011 *
  0.0000 0.0000 0.0000 0.0000 0.0030 0.0392 9.7030
  
  For wn=[340 360], the results are:
  b =
  1.0e+015 *
  0.0000 0 0.0000 0 0.0000 0 1.8338
  a =
  1.0e+015 *
  0.0000 0.0000 0.0000 0.0000 0.0000 0.0006 1.8338
  
  where the transfer function is
  
  H(s) = B(s)/A(s) = [b(1)s^n + b(2)s^(n-1) + ... + b(n+1)]/[s^n + a(2)s^(n-1) + ... + a(n+1)]
  
  Pls help me out, thx.
  
  I've checked with my supervisor, and he told me to use code C, that is to change the MATLAB instructions into code C instructions, in order to program it into the PIC.
  
  Is it possible to change MATLAB instructions to code C instructions?
  
  What is the form of code C file needed so that it can be programmed into the PIC? Is it MEX file or .exe file?
• 

  wassup

  OH GOD ! That really doesn't work out buddy. C files from MATALB require a lot of libraries and porting that into PIC will be impossible. .mex n .exe are executables not C files.
  Also please let me know about the signal you are filtering. Are you filtering it in real time? if not how big the signal ? In that case you will going no where with PIC (sorry to say this, switch to dsPIC).
  This is what you can do for now, remember this is not a very good way to implement filters.
  1) Find h[n] from matlab. Take the array convert it into 8 bit fixed point in matlab. You will have to play with the numbers to get a good approximation. Store this as a array in C.
  2)Implement a convolution function is C. This can be compiled in PIC. But I will tell you it will be very slow, since PIC doesnt have a multiply instructions ! The function will have two arguments. The filter array and the signal you are filtering.
  
  After this you will again have to fool around with numbers to get a good result. You can avoid mulitpicaltion if your filter coefficients are mutliples of 2. So approximate the fixed point numbers. Hope you got the idea.
  
  I really need to know what project you are doing, so I can suggest you better alternatives.
• 

  kaibin

  My project is The Development of Band-stop Filter for Vibration Control Using PIC(dsPIC now, since PIC is not able to handle the algorithms) Microcontroller. The Band-stop filter is used to filter a bang-bang torque input which will then be inserted into a flexible-link modal.
  
  The flexible-link modal has a state-space parameters of
  A = [0, 0, 0, 1, 0, 0;
  0, 0, 0, 0, 1, 0;
  0, 0, 0, 0, 0, 1;
  0, -6175.8, -0.135271x10^7, 0, 7.8681, -341.14;
  0, 21700.8, 0.257311x10^7, 0,-2.5541, 745.786;
  0, -1629.67, -147554, 0,-0.334002, -46.5154;]
  
  B = [ 0;
  0;
  0;
  1173.24;
  -1128.74;
  23.8429;]
  
  C = [1 1 1 0 0 0]
  
  D = [0]
  
  All of the following are done in MATLAB simulink:
  When the unfiltered bang-bang torque input is inserted into the flexible-link modal, a magnitude-frequency response output will be shown. The two peak frequencies are natural frequencies that will cause the flexible-link to vibrate.
  
  To reduce the vibration, the bang-bang torque input is needed to be filtered using the band-stop filter.
  
  I've asked some advice from a lecturer, and it seems to me that the only way to make this project work is to convert the MATLAB instructions to code C language and program it into the dsPIC. He also mentioned that PIC has limited decimal places. And he said to me it will be tough and the probability to success is just a mere 20%.
  
  Can you provide any useful MATLAB to code C websites to me for study? I am stuck with no progress at all with the project.
  
  Please do suggest other alternatives to me. Thanks.
• 

  yhsam

  kaibin is one of my project group member. he is designing the code of filter, and me is designing the code of positive input shaping.. actually our project is divided into two stage .. first stage, we are use the matlab to design the simulation of flexible manipulator model, and also the positive input algorithm ... below is my simulation
  
  
  
  stage 1 was done .. now, we are doing the stage 2.. The positive input shaping algorithm is embedded into dsPIC.. and the positive input shaping block in matlab is replace by the dsPIC... this also means that the flexible manipulator simulation block in matlab will " calculate " the angle , displacement, valocity, etc from the dsPIC, which is embedded with positive input shaping and filter .
  
  here is my positive input shaping code in matlab
  
  starting_time=0;
  simulation_time=4;
  sampling_time=0.001;
  t=starting_time:sampling_time:simulation_time;
  
  
  for i=1😔0.2/sampling_time)+1
  u(i,1)=0;
  end
  for i=(0.2/sampling_time)+1😔0.5/sampling_time)+1
  u(i,1)=0.3;
  end
  for i=(0.5/sampling_time)+1😔0.8/sampling_time)+1
  u(i,1)=-0.3;
  end
  for i=(0.8/sampling_time)+1😔4/sampling_time)+1
  u(i,1)=0;
  end
  
  
  % Positive ZV shaper (2-impulse)
  % mode 1
  
  pi=22/7;
  z1=0.0086;
  k1=exp((-z1*pi)/((1-z1^2)^0.5));
  wn1=94;
  wd1=wn1*(sqrt(1-z1^2));
  
  %Determine the amplitudes and time location of the input shaper
  
  ip=2;
  
  tt1a(1)=0;
  tt1a(2)=pi/wd1;
  A1a(1)=1/(1+k1);
  A1a(2)=A1a(1)*k1;
  
  tt1a=tt1a./0.001;
  tt1a=round(tt1a);
  tt1a=tt1a.*0.001;
  
  for i=1
  v1a(i,1)=A1a(1);
  end
  
  ni=1;
  while ni<=ip-1
  for i=((tt1a(ni)/sampling_time)+2)😔(tt1a(ni+1)/sampling_time)+1)
  v1a(i,1)=0;
  end
  for i=(tt1a(ni+1)/sampling_time)+1
  v1a(i,1)=A1a(ni+1);
  end
  ni=ni+1;
  end
  
  for i=((tt1a(ni)/sampling_time)+2)😔(4/sampling_time)+1)
  v1a(i,1)=0;
  end
  
  %mode 2
  
  pi=22/7;
  z2=0.0086;
  k2=exp((-z2*pi)/((1-z2^2)^0.5));
  wn2=344.70;
  wd2=wn2*(sqrt(1-z2^2));
  
  %Determine the amplitudes and time location of the input shaper
  
  ip=2;
  
  tt2a(1)=0;
  tt2a(2)=pi/wd2;
  A2a(1)=1/(1+k2);
  A2a(2)=A2a(1)*k2;
  
  tt2a=tt2a./0.001;
  tt2a=round(tt2a);
  tt2a=tt2a.*0.001;
  
  for i=1
  v2a(i,1)=A2a(1);
  end
  
  ni=1;
  while ni<=ip-1
  for i=((tt2a(ni)/sampling_time)+2)😔(tt2a(ni+1)/sampling_time)+1)
  v2a(i,1)=0;
  end
  for i=(tt2a(ni+1)/sampling_time)+1
  v2a(i,1)=A2a(ni+1);
  end
  ni=ni+1;
  end
  
  for i=((tt2a(ni)/sampling_time)+2)😔(4/sampling_time)+1)
  v2a(i,1)=0;
  end
  
  
  imp1a=conv(v1a,v2a);
  impa=imp1a(1😔4/sampling_time)+1);
  
  shp1a=conv(impa,u);
  PZV=shp1a(1😔4/sampling_time)+1);
• 

  wassup

  OK guys, let me make few things simpler for you.
  @#-Link-Snipped-# I don't know why he is asking you to convert the whole Matlab stuff into C and then porting it to dsPIC. It's doesn't make any sense. I will first tell you how to implement the filter ! @#-Link-Snipped-# I don't understand what you are saying, I need to look into more detail. One of you guys can get in touch with me through mail. But first the filter implementation.
  1) Don't implement filter design in dsPIC !! You already have the filter design from MATLAB.
  2) Now just use imp function in matlab and find h[n]
  3) Find u[n] of bang-bang input.
  4) Store both of them in array
  5) Implement convolution algorithm in C (dsPIC)
  Simple isn't it ?
  
  Now are you guys simulating every module ? No external hardware ? flexible-link modal this is external right ?
• 

  wassup

  Your system is too simple to port MATLAB code to dsPIC. Just implement convolution you shall be done. It is just 3 for loops.
  But if you really want, you should use realtime toolbox which will convert simulink model to dspic code.
  dsPIC (microchip.com) has an example on this one, but I have never used it, please do check
• 

  yhsam

  yes ... i have done simulating in every module, and no external hardware, kaibin and me are using the flexible manipulator form matlab simulation block.
  
  i am apologize about my english and cannot explain clearly.
  stage 1 was done .. now, we are doing the stage 2.. The positive input shaping algorithm is embedded into dsPIC.. and the positive input shaping block in matlab is replace by the dsPIC... this also means that the flexible manipulator simulation block in matlab will " calculate " the angle , displacement, valocity, etc from the dsPIC, which is embedded with positive input shaping and filter .
  
  the realtime toolbox is get from matlab ?! but i didn't see it ... but i founded a application named " realtime workshop " is it ?!!
• 

  wassup

  OK I postive input shaping seems simple. I guess you can implement that in C without much fuss.
  and yeah filter I already told. There will be examples in dsPIC (application note) for convolution, please check
• 

  yhsam

  sorry late to reply.. because i am busy with my exam.. my supervisor is decided to use the PIC18LFk50 and with FTDI . its it any comment the programming code for FTDI ?! supervisor suggest me try to design the code for this equation first ..
  
  
  did u all guys have any idea to design this impulse ?!?! i have read many example ... but its doesn't example similar this ...
  
  thanks q for your help...
  here is my email address ..
  the kaibin email :
  
• 

  yhsam

  any Expert can help me ?! this project is important for me !!
• 

  wassup

  There are two books you can read to implement this.
  One is DSP using Matlab by S K Mitra and this #-Link-Snipped-#
• 

  adinickluv

  hey guys can anybody tell me where can i download malab software.
  I also need it..
• 

  wassup

  haha nice try Matlab isn't free ! Crazyengineers don't support piracy 😀
  You can download and try octave which is free and compatible with, #-Link-Snipped-#
  
• 

  yhsam

  download ? .. u may download the trial version from mathwork website. but if u want to get the full version, it is illegal. u need to purchase the software.
  
  for wassup:
  thanks q for your recommend book.. its quick useful for my project..
• 

  yhsam

  i have an idea the simplest way, how about if i convert the algorithm in matlab editor convert to C code ?! and embedded into PIC ?! its more simple and not need to reprogramm right ?! same right wassup say. anybody can help me what should i do this step ?!!
  
  i have search in google. founded that its have two tool can do this convert step. one is realtime workshop and another one is catalytic .. which one is better ?!