Create the Project

After installing the software, connect the PIC24F Curiosity Development Board to a USB port on your computer. Create a new standalone project in MPLAB^® X for a PIC124FJ128GA204. The PIC124FJ128GA204 is the microcontroller on the PIC24F Curiosity Development Board. When the project creation wizard asks for a hardware tool (Step 2 in the New Project window), select the PIC24F Curiosity Board as displayed below.

After the project has been created, the Projects tab in the upper-left corner of the IDE shows that the project has been created with no source or header files.

Open MCC

Open MCC under the Tools > Embedded menu of MPLAB X IDE.

MCC will place a Resource Management tab on the left-hand side of the IDE. Inside this tab, you will see a section for Project Resources and Device Resources. For each MCC-generated project, you will need to verify/modify the System Modules under the Project Resources window.

Add a timer and the ADC to the list of peripherals being used in the application

From the Device Resources section of the MCC Resource Management window, locate Timer1 (TMR1).

Double-click on TMR1 to add this peripheral to the resources available to the project.

Repeat the step to add ADC1 [ PIC24F / dsPIC33 / PIC32MM MCUs]

Set the Project Resources

There are three system elements which need attention:

• Interrupt Module: controls the MCU's interrupts.
• Pin Module: configures the I/O pins.
• System Module: selects and configures the clock source for the MCU.

Interrupt Module

This section displays and controls the priority and the enable bit for each interrupt. This section will be reviewed after the Timer and ADC peripherals are configured (Step 6).

System Module

The System Module allows the user to configure the MCU's clock, the Watchdog Timer (WDT), and make changes to the debug pin assignments. This feature of the PIC24F MCU has numerous options, which are typically modified to fit the needs of the application. MPLAB^® Code Configurator (MCC) provides default settings if no changes are selected by the developer. For this lab, accept the default clock settings:

• 8 MHz Internal Free Running Oscillator with no Prescaler, but a 1:2 Postscaler (4 MHz Fosc)
• Watchdog Timer - disabled
• Unchanged debug pins

To verify the default settings, click on the System Module tab and verify the following selections have been made:

We will now set the pin connected to LED1 (RA9) as an output pin. In the Grid View window, click on the output box under RA9. The grid view will display the padlocks in green, indicating these pins have been configured for use.

1. Ensure that RA10 is set as an output pin.
2. Rename RA10 to "LED".
3. Select RC0 in the ANx row as the analog signal (this pin is connected to the pot).
4. Leave the analog change name channel AN10 unchanged.

Confgure Timer1 for 1/2 Second Period with the Interrupt Enabled

We will start with the timer period at 1/2 second and will modify it based upon the ADC value with the F_osc set at 2 MHz, TMR1 will be unable to generate a 1/2 second period as the 16-bit counter will overflow before 1/2 second. To lengthen the period window for this timer, we will prescale the system clock by 0256 to down the timer. Once the timer is slowed, we will be able to select the 1/2 second timer period.

Select TMR1 from the Project window and make select the following settings:

Verify the Priority of the Timer Interrupt

Select the Interrupt Module icon in the Project Resources window to verfiy that TMR1 interrupt has been enabled.

Configure the ADC unit

• Set the trigger source to: Clearing sample bit and sampling and begins conversion
• Set the output format to: Absolute decimal result, unsigned, right justified
• Enable the ADC.
• Enable Auto Sampling.
• Verify the name given the I/O pin.

Generate Code

To generate the code, click the Generate button on the MCC window.

The projects tab will show the source and header files created by MCC.

The main(void) is located within the main.c file. main(void) calls the MCC generated SYSTEM_Initialize() function before it enters the while(1) loop.

SYSTEM_Initialize() in turn calls PIN_MANAGER_Initialize(), INTERRUPT_Initialize(), CLOCK_Initialize, ADC1_Initialize, and TMR1_Initialize(). These functions initialize the ADC, TMR1, set up the I/O pins, and establish the interrupt writing to the device's function registers.

Modify the MCC-generated Code to Complete the Application

We will now modify main.c.

An inspection of MCC-generated header file pin-manager.h, adc1.h, and tmr1.h shows that MCC has created several control functions useful for our applications.

pin-manager.h Function Prototype:

• LED1_toggle();: changes the value of the I/O pin connected to the LED1.

tmr1.h Function Prototypes:

• TMR1_Start(): starts the operation of TMR1.
• TMR1_SetInterruptHandler(): registers a user defined function as the ISR for TMR1.
• TMR1_Period16BitSet(): sets the period length for TMR1.

adc1.h Function Prototypes:

• ADC1_ChannelSelect(channel): selects the pin to be connected to the ADC unit.
• ADC1_Stop(): triggers the conversion by clearing the sample bit.

- Yes, ADC1_Stop() will actually start an ADC conversion. While the name of this function is counter-intuitive, when Auto-Sampling is enabled, stopping the sampling begins the conversion.

• ADC1_IsConversionComplete: returns a True if the ADC unit has finished the conversion.
• ADC1_ConversionResultGet: returns the value of the last conversion.

Make the following modifications to main.c

1. Insert the text #include "mcc_generated_files/mcc.h" near the top of the file.
2. Create a function void My_ISR(void); which toggles the LED, then call ADC1_Stop.
3. Register My_ISR as the ISR for TMR1 by calling TMR1_SetInterruptHandler(My_ISR).
4. Insert the code in main.c below to start the ADC conversion and put the results into the timer Period register.

main.c

#include "mcc_generated_files/system.h"
#include "mcc_generated_files/mcc.h"  //##### must be added #####

    void My_ISR(void)
      {
        LED_Toggle();
        ADC1_SoftwareTriggerDisable();                    // trigger next conversion
      }

    int main(void)
      {
        SYSTEM_Initialize();
        ADC1_ChannelSelect(channel_AN10);
        ADC1_SoftwareTriggerDisable();                  // begin first conversion
        TMR1_SetInterruptHandler(My_ISR);
        TMR1_Start();
        while (1)
          {
            if (ADC1_IsConversionComplete(channel_AN10)){
                if (ADC1_ConversionResultGet(channel_AN10)==0)
                     TMR1_Period16BitSet(1);
                else
                    TMR1_Period16BitSet(ADC1_ConversionResultGet(channel_AN10));
            // application code goes here
            }
          }
        return 1;
      }

10

Build, Download and Run the code

To run the program on the development board, click on the Make and Program Device Main Project button . This will build the program into the flash memory of the PIC^®. The output window of the IDE will tell you when the device has been programmed and the application is running.