With the dsPIC blockset, we get from the simulink model:

Explorer 16 Development Board with dsPIC 33FJ256GP710 or PIC 24FJ128GA010

Configure Simulink

Set the dsPIC configuration

Open the Master block.

Master block configuration

Blinking Led

A counter is used to make blinkind leds. Its sample time set to 1 for 1 seconde makes it count at 1Hz. The model has blocks with a sample time of 5ms (model main sample time) and others with 1 seconde (which is a multiple (X200) of the model sample time). Thus, this is a multirate model.
Color are used to see the different sample time (option in Format==> Ports/Signal display ==> 'Sample Time Color' .

The counter is configured to count from 0 to 3. Bitewise logic and extract bit 0 and bit 1 of the counter. These bits are sent to the Digital Output Write bock.

Bitewise Operator extracting bit 0 of counter (0.5Hz blinking led)	Digital Output Write (Port A connected to 8 leds of the Explorer 16 Dev Board)

The Digital Output Write block switch on or off Leds connected to the PIN A0 or A7 of the dsPIC depending on the block's input values. The refresh rate of this block is 200Hz (5ms : Red).

Note : We could use two separate blocks : one for the port (A0 ) with a refreshing rate of 1Hz and another one for the third led (connected to A7) with a refreshing rate of 200Hz.

Digital Input

The Digital Input block's output value is 0 while the button is pushed. The diagram make the LED blink when the button is pushed.

Digital Input Read (Port D6 connected to the left push button of the Explorer 16 Dev Board)

Sampling and Filtering data from ADC

Potentiometer is connected to the AN5 PIN. We used here the 10 bit ADC converter of the dsPIC but we using the 12 bits ADC is possible and switching from one to the other is as simple as selecting which one you want to use (one click solution !).

ADC Dialog box

The value converted is an unsigned 16 bit variable where only the 10 lower bites are used.
The block create the variable 'ANmax' in the workspace that has the value of the max value taken by the output of the block. If using the 10bit ADC, the max value is 2^10 = 1024. When using the 12 bit ADC, the max value is 2^12 = 4096.

The output value of the ADC block is compared to ANmax/2 that is the mid position of the potentiometer (corresponding to a tension of 1.65V). When the value converted is greater than ANmax/2, the led connected to the port A7 switched on otherwise it is switched off.

The output value of the ADC block is also filtered with two different filters.
One first order filter with a frequency cut off at 1Hz designed with the matlab command line >>c2d(tf([6],[1 6]),.005,'tustin') (need the Control System Toolbox)
and One first order filter with a frequency cut off at 10Hz designed with the matlab command line >> c2d(tf([60],[1 60]),.005,'tustin')

The matlab filter block used works using double data type. It needs double data types at its input and provides double data types at its output. Two conversion blocks are used. Note however that calculation using double are time consumming for the dsPIC and it is preferable to realize fixed point filter. The fixed point toolbox is very helpfull to make precise and efficient calculation using only fixed point variables.

Logging & Plotting data in Matlab (dsPIC side)

Data transmition is done using the UART dsPIC peripheral and one PC serial COM port. The demo board RS-232 serial port must be connected to one COM port of the PC.

First of all, the baud rate of the UART must be set. For each baud selected, the Info text box show the real baud obtained the the % error from the selected baud. The % error must be low (absolute value of error belo 3%) for the RS-232 serial transmition to work properly. Using a 8Mhz quartz with no PLL (obtaining 4 MIPS) the fastest workable baud rate is 19200.

The UART port of the board with the appropriate max3232 component is connected to the UART 2 of the dsPIC.

UART configuration dialob box	TX Output Multiplexed for Matlab / Labview dialog box

Once the UART is configured, the block to send data from the dsPIC to Matlab is configured. We set 3 channel to send 3 different data.
At low level portocol, the three data are uint16 and needs 3 char each to be sent. All data will be logged since at each time step, 9.6 char can be sent and 9 are required (3X3). Data will be logged with the same sampling rate than the block : 200Hz. It is possible to use more channel but this will lead to data loss (not important for visualisation or debugging).

Once the model is generated, compiled and the .hex file is loaded into the dsPIC, data will be logged and view with the matlab User Interface created. This one can be opened either in double clicking onto the block 'Interface Tx-Matlab' or typing at the matlab prompt >> rs232gui

Generate C code, Download the hex file into the dsPIC

Once the model is finished, C code is generated and compiled : click on the 'Incremental build' button or press 'Ctrl+b'. The .hex file obtained in the same directory of the. mdl file can be loaded into the dsPIC using MPLAB : go to MPLAB, File==> Import and select the .hex file, then, download it into your dsPIC using either ICD2, Real ICE or others...

html report with the C code generated can be generated. Go to Simulation ==> Configuration Parameters ==> select Real Time Workshop on the left column and check the option Generate HTML report on the right pannel. The model was compiled with Matlab 2007.

Logging & Plotting data in Matlab (PC side)

The .hex file is loaded into the dsPIC, you get two led blinking at 1Hz and 0.5Hz and the Explorer 16 Demo board is connected to one PC COM port.

Open the rs232gui user interface ( click twice on the block 'Interface Tx-Matlab' or type rs232gui at the matlab prompt.

RS232gui User Interface to log and plot data

Set the COM port to the one you are using (PC side) and set the baud rate to 19200 (same as dsPIC). No flow control used. Then,click on Connexion, wait 3 seconds and click on the Start button. On some PC, Matlab closed if you click on Connexion while data are being sent from the dsPIC to the PC. In that case, disconnect the dsPIC before pushing the Connexion button.

Moving the Potentiometer, you will obtain the following graphic with three curves : the blue curve is the raw data (unfiltred), the red curve is the data filtred at 1Hz and the green curve is the data filtered at 10Hz.

Raw and filtred data (at 1Hz and 10Hz) from the ADC 5 channel connected to the potentiometer

Animation showing Raw and filtred data (at 1Hz and 10Hz) from the ADC 5 channel connected to the potentiometer

Next...

You can now modify the model and compile it with the free demonstration version available. Note however that you could not add PINs to the model due to the 6 I/O PINs limitation of the downloadable version. You could however remove used PIN to replace them by others.

For any question or unclear point, feel free to ask technical question on the forum.