Instructables
some code to let MATLAB talk to a PIC16f877 via the serial port. This isn't that hard nor is it much code, but I spent a decent amount of time figuring it all out (starting from scratch), so I figured it would be helpful. Enjoy.
 
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Step 1: Code with comments

below is some code I pasted in. Download the .txt file if you want the code. See the pictures for help witht he serial interface. One shows the 22kohm resistor method of connecting your serial port to a PIC. The other shows the max232 method of connecting your serial port to a PIC.

With serial connections the most common problem is not setting the computer and the PIC to the same Baud Rate, so make sure you do that (as it's done in my code).
Also, make sure you've connected all of the GNDs together (PIC, MAX232, and Computer GNDs all connected).
Also, make sure that you're using the right capacitor value for the max232 (max232 vs. max232A), see diagram in the instructable for the proper values.
Also, make sure that your computer is sending the values you think it is sending. To do this, stick wires into your DB9 cable to make a serial loopback. This will make the computer get back exactly what it has just sent. Here's a diagram of how to wire this up:
http://electrosofts.com/serial/loopback.jpg
So make your matlab code do a serial read right after the serial write.
You can also use free serial port monitoring software to makesure serial communications are occuring properly (here's one example http://www.batchconverter.com/FreeSerialPortMonitor-download-20643.shtml).

Anyway, here's the code:

%##########################################################################
%########################--MATLAB CODE--###################################
%##########################################################################
%This code assumes that you have MATLAB hooked up to a PIC microcontroller via the PC's serial port through a
%MAX232 IC _OR_ if you don't use a max232 all you need is a 22 kohm limiting resistor on
%the serial line which connects the computer to the PIC (aka Pin 3 and/or Pin 2, see below).
%Pin 3 or the DB-9 port is the TX line, aka the line that carries serial data from the PC to the PIC.
%Pin 2 carries serial data the other way (PIC to PC) if you want to do that.
%Pin 5 is the DB-9 ground pin which you should use to connect the PC ground with the PIC ground.
%This code also assumes that you're using COM3 for serial communication with the PIC.

SerPIC = serial('COM3'); %<--change this appropriately
set(SerPIC,'BaudRate', 9600, 'DataBits', 8, 'Parity', 'none','StopBits', 1, 'FlowControl', 'none');
fopen(SerPIC); %--open the serial port to the PIC

fprintf(SerPIC, '%s', '003'); %--send a _three_ digit string to the PIC with no terminator ('%s')
%-- 003 = 00000011 in binary, so first two LEDs of PIC will light

fclose(SerPIC) %--close the serial port when done
delete(SerPIC)
clear SerPIC

%NOTE 1:
%if MATLAB ever gives a serial error, it will most likely say 'unable to open serial port' next time you
%run the program, so you have to restart MATLAB
%NOTE 2:
%the number must always be sent as a three digit number because for some reason I couldn't get my PIC to receive
%the number when it wasn't of a specified length (see PIC code: DEC3)

%==========================================================================
%==========================================================================

'##########################################################################
'#############################--PIC16F877 CODE--###########################
'##########################################################################
'This code assumes you have the PIC16F877 set up with one LED on each line of Port D (8 lines).
'This way the PIC will light up a different pattern of LEDs according to the number send via serial from MATLAB.
'Each LED should be in series with a 470 ohm resistor (see pic below)
'_
' '
' '------LED---\ 470 ohm
'PIC' >------/\/\/\------GND
' '------LED---/
'---'
'
'This code also assumes that you have the TX line of the DB-9 serial port connected to pin 0 of port C (PORTC.0)

Include "bs2defs.bas" 'has some useful stuff in it

'DEFINE OSC 4 'Oscillator speed in MHz, this isn't needed I guess
SerI var PORTC.0 'make an easy name to refer to the serial pin

TRISD = %00000000 'set PortD as an output port
PortD = %00000000 'set LED port to all zeros

GetGhost:
Serin2 SerI, 84, (DEC3 B0) 'get a three digit number from serial pin and put it into B0 variabl
PortD = B0 'set the lines of PortD according to this three digit number
GOTO GetGhost

'===========================================================================
'===========================================================================
crapper5 years ago
thanks for the instructable. but i have problem. my laptop doesnt have a serial port, only usb. how can i connect to my laptop? i dont think i can use a usb-serial converter since its +5v 0. helpppp
leevonk (author)  crapper6 months ago

I used a usb-serial converter for PIC programming, so it should work in this case too. this one works for me: http://www.amazon.com/Tripp-Lite-Serial-Adapter-U2...

"Tripp Lite USB to Serial DB9M Adapter"

hani_aast5 years ago
I want the complete circuit how we connect max232 with pic with serial

hi hani i got this link from google search go through that it will help you lotsthey have c code with video tutorial http://www.nbcafe.in/interfacing-proteus-with-matlab/

hi everybody;
i interface my pc with serial port with bootloder has pic18f2550 to control DC motor direction (H_brige),simulation in protuos work well and rs232 with max232 work too,but problem when i loaded program to board does not work?
there is no voltage on my outpot
thanks with regards
hiii 2 all...i have 2 questions.
1 is there any way i can interface matlab with wifi??
2 is there any way i can interface matlab with the serial port of computer without using any micro controller??

i would be very thankful to the one who answers my question....
regards
shoaib
Hi..
My system has 6 servos and 1 dc motor. Value for servos to turn will always change according to the program i write in Matlab.So mean that i have to interface my servo motor to PIC16F877A by connecting servo controller to it right?
And for DC motor i have to build H-bridge and attached them on PIC as usual?

How to write program on this in matlab? how to send signal to move the motor?
please help!!i have been looking for this about a month...hu hu
duyngdang6 years ago
Help me with COM in Matlab! In Matlab command window,I type: set(COM1,'BaudRate',9600,'DataBit',8,'Parity','none','StopBit',1,'Flowcontrol','none'); fopen(COM1) then error: ??? Undefined function or variable 'COM1'. Some body can help me about that! I'm very new with Matlab and conputer interface! Thanks!
my dear,you must type as below for creating a serial port object :
s=('COM1','BaudRate',9600,'DataBit',8,'Parity','none','StopBit',1,'Flowcontrol','none');
fopen(s)

where s is your object !!
Now I can open port with Matlab. Now I have to put an hex file to Pic16F88? Would you please share for me the the hex file to put in the Pic16F877? I have programmer kit and soft for pic but I don't have any software to program and convert to hext files After that, I have to put some led to pins of pic16F877 for this command: fprintf(SerPIC, '%s', '003'); ? Would you please send me the schematic for that? I'm a mechanic guy,so I'm trying to know about computer interface. Please help me for that! Thanks!
leevonk (author)  duyngdang6 years ago
uhm, how bout using my code that's staring you right in the face on the next page:

SerPIC = serial('COM3'); %<--change this appropriately
set(SerPIC,'BaudRate', 9600, 'DataBits', 8, 'Parity', 'none','StopBits', 1, 'FlowControl', 'none');

!!!!!!!!
note the very important SerPIC = serial('COM3');
!!!!!!!!
I want to continuously send a x and y coordinate from Matlab via a USB-RS232 cable to a pan-tilt servo assembly controlled by an ooPIC-R. Does the ooPIC-R convert the RS232 +-10V to TTL +-5V? Should the concept of your code work for this application? I can send one value from Matlab and get a servo to react but the system acts up when I try to send values continuously. Sometimes I get a "timed out" error in Matlab.
behrouz20076 years ago
I want use 9bit USART (9th bit set) for sending command to PIC and (9th bit zero) for sending data to PIC. So i want use Parity bit of serial port as 9th bit.
But when i execute herein commands in MATLAB 6:
>> e=serial('COM1')
>> fopen(e)
>> set(e,'Parity','mark')
This error occured:

??? Error using ==> serial/set
Parity could not be set to the specified value.

Please help me. Why i can not change parity to 'mark' and 'space'.
duyngdang6 years ago
Now I can open port with Matlab. Now I have to put an hex file to Pic16F88? Would you please share for me the the hex file to put in the Pic16F877? I have programmer kit and soft for pic but I don't have any software to program and convert to hext files After that, I have to put some led to pins of pic16F877 for this command: fprintf(SerPIC, '%s', '003'); ? Would you please send me the schematic for that? I'm a mechanic guy,so I'm trying to know about computer interface. Please help me for that! Thanks!
jnk1017 years ago
gr8 begining
chk out :
http://www.dspaceinc.com/ww/en/inc/home/products/systems/controld.cfm
have u come across diy / open source for this stuff
really keen on this stuff

finly jnk1017 years ago
Hello, that's a great tutorial. Do you have any tutorial about how to display signal generated by function generator and A/D converted by PIC ? The PIC will be connected to the PC using serial. Thank you.
ppsh047 years ago
Thank you for the experience you have shared here. This post is really effective for my program. :D Hope you can contribute more. Good Luck!
ferasmetib7 years ago
would you please add this file bs2defs.bas and in what software enviromint is the pic code : mplap ide, picbasic,....?
leevonk (author)  ferasmetib7 years ago
I used MPLAB with PICBasic set as the compiler. If you have the PICBasic compiler you'll have the bs2defs.bas file, if you don't have PICBasic the file is useless so I won't post it (I'm not sure if it's legal to post it). It's not really an important file anyway, If you delete its include from my code, all you have to change is to declare your own variable in place of B0 (B0 is a predefined variable when using bs2defs.bas).