Introduction: MATLAB to PIC Serial Interface
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.
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
'===========================================================================
'===========================================================================
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
'===========================================================================
'===========================================================================
