10.2 Bare Metal Code
The application with bare metal code will have the same behavior as the MCC generated code.
The first step will be to configure the microcontroller to disable the Watchdog Timer (WDT) and to enable Low-Voltage Programming (LVP).
#pragma config WDTE = OFF /*disable Watchdog*/
#pragma config LVP = ON /* Low voltage programming enabled, RE3 pin is MCLR */Then, the following variables need to be defined:
#define Timer2Period 0x2F /* TMR2 Period is 100ms */ #define Timer4Period 0xF1 /* TMR4 Period is 500ms */ #define DesiredThreshold 300 /* Desired threshold value */ #define MaxThreshold 500 /* Maximum threshold value */ #define AnalogChannel 0x00 /* Use ANA0 as input for ADCC */ volatile uint16_t adcVal; /* ADCC global result value */
The CLK_Initialize function initializes the HFINTOSC
internal oscillator:
static void CLK_Initialize(void)
{
/* set HFINTOSC Oscillator */
OSCCON1 = 0x60;
/* set HFFRQ to 1 MHz */
OSCFRQ = 0x00;
}The PPS_Initialize function has the role to configure the
RC7 peripheral select as input for TMR4:
static void PPS_Initialize(void) { /* Set RC7 as input for TMR4 (T4IN) */ T4INPPS = 0x17; }
PORT_Initialize configures the RC7 digital input and RE0
output pins used for LED0:
static void PORT_Initialize(void)
{
/* Set RC7 pin as digital */
ANSELC = 0x7F;
/* Set RE0 pin as output */
TRISE = 0x06;
/* Enable weak pull-up on pin RC7 */
WPUC = 0x80;
}ADCC_Initialize configures the TMR2 to be an
auto-conversion trigger and enables the ADCC Interrupt flag:
static void ADCC_Initialize(void)
{
/* ADACT Auto-Conversion Trigger Source is TMR2 */
ADACT = 0x04;
/* ADGO stop; ADFM right; ADON enabled; ADCONT disabled; ADCS FRC */
ADCON0 = 0x94;
/* Clear the ADCC interrupt flag */
PIR1bits.ADIF = 0;
/* Enabling ADCC interrupt flag */
PIE1bits.ADIE = 1;
}The TMR2_Initialize function sets the clock source and the
registers needed to generate an 100 ms period:
static void TMR2_Initialize(void)
{
/* TMR2 Clock source, LFINTOSC (00100) has 31 kHz */
T2CLKCON = 0x04;
/* T2PSYNC Not Synchronized; T2MODE Starts at T2ON = 1 and TMR2_ers = 0; T2CKPOL Rising Edge */
T2HLT = 0x02;
/* TMR2 external reset is TMR4_postscaled */
T2RST = 0x02;
/* TMR2 ON on; T2 CKPS Prescaler 1:64; T2 OUTPS Postscaler 1:1
Minimum timer period is 31 kHz/64 = 2.064516 ms */
T2CON = 0xE0;
/* Set TMR2 period, PR2 to 100ms */
T2PR = Timer2Period;
/* Clear the TMR2 interrupt flag */
PIR4bits.TMR2IF = 0;
}The TMR4_Initialize function sets the clock source and the
registers needed to generate a 500 ms period:
static void TMR4_Initialize(void)
{
/* TMR4 Clock source, LFINTOSC (00100) has 31 kHz */
T4CLKCON = 0x04;
/* T4PSYNC Synchronized; T4MODE Resets at TMR4_ers = 1; T4CKPOL Rising Edge */
T4HLT = 0x87;
/* TMR4 External reset signal by T4INPPS pin */
T4RST = 0;
/* TMR4 ON on; T4 CKPS Prescaler 1:64; T4 OUTPS Postscaler 1:1
Minimum timer period is 31 kHz/64 = 2.064516 ms */
T4CON = 0xE0;
/* Set TMR4 period, PR4 to 500ms */
T4PR = Timer4Period;
/* Clear the TMR4 interrupt flag */
PIR4bits.TMR4IF = 0;
/* Enabling TMR4 interrupt flag */
PIE4bits.TMR4IE = 1;
}The following initialization function will safely enable the Global and Peripherals interrupts, after all modules have been initialized with proper settings:
static void INTERRUPT_Initialize(void)
{
INTCONbits.GIE = 1; /* Enable Global Interrupts */
INTCONbits.PEIE = 1; /* Enable Peripheral Interrupts */
}This function handles the two interrupts, checks the status of the Interrupt
flag, and then calls the TMR4_Interrupt or
ADCC_Interrupt functions:
static void __interrupt() INTERRUPT_manager (void)
{
/* Interrupt handler */
if (INTCONbits.PEIE == 1)
{
if (PIE4bits.TMR4IE == 1 && PIR4bits.TMR4IF == 1)
{
TMR4_Interrupt();
}
else if (PIE1bits.ADIE == 1 && PIR1bits.ADIF == 1)
{
ADCC_Interrupt();
}
}
}The ADCC_Interrupt function first clears the Interrupt flag,
toggles the LED0 (this will happen with Timer2 Period frequency), and then reads the
ANA0 analog channel.
static void ADCC_Interrupt(void)
{
/* Clear the ADCC interrupt flag */
PIR1bits.ADIF = 0;
if (adcVal < DesiredThreshold)
{
/* Toggle LED0 at the Timer2Period frequency */
LATEbits.LATE0 = ~LATEbits.LATE0;
}
/* Get the conversion result from ADCC AnalogChannel */
adcVal = ADCC_ReadValue(AnalogChannel);
}static uint16_t ADCC_ReadValue(uint8_t channel)
{
ADPCH = channel; /* Set the input channel for ADCC */
/* TMR2 is trigger source for auto-conversion for ADCC */
return ((uint16_t)((ADRESH << 8) + ADRESL));
}
The TMR4_Interrupt function first clears the Interrupt flag
(if the ADCC read value is above the maximum threshold and if the RC7 pin is pulled to
GND for more than 500 ms), TMR4 will stop TMR2 and LED0 will blink for a 500 ms period,
as long as RC7 is tied to GND.
static void TMR4_Interrupt(void)
{
/* Clear the TMR4 interrupt flag */
PIR4bits.TMR4IF = 0;
/* HLT trigger condition: if adcVal > MaxThreshold and pin RC7 is pulled-down */
if (adcVal > MaxThreshold)
{
/* Toggle LED0 at the Timer4Period frequency */
LATEbits.LATE0 = ~LATEbits.LATE0;
/* HLT will stop TMR2 that also stops ADCC */
/* Stop the Timer by writing to TMRxON bit */
T2CONbits.TMR2ON = 0;
}
}The next code in the void main function, is an infinite
loop (using a while(1)) to check for the ADCC value, using an
“if” statement.
void main(void)
{
/* Initialize the device */
CLK_Initialize(); /* Oscillator Initialize function */
PPS_Initialize(); /* Peripheral select Initialize function */
PORT_Initialize(); /* Port Initialize function */
ADCC_Initialize(); /* ADCC Initialize function */
TMR2_Initialize(); /* TMR2 Initialize function */
TMR4_Initialize(); /* TMR4 Initialize function */
INTERRUPT_Initialize(); /* Interrupt Initialize function */
while (1)
{
if ((adcVal > DesiredThreshold)&&(adcVal < MaxThreshold))
{
/* turn LED0 ON by writing pin RE0 to low */
LATEbits.LATE0 = 0;
}
}
}This will check if the read value from the Potentiometer (POT Click) is between two values. If so, the LED0 will turn on without blinking with a frequency. The ADCC interrupt is triggered by TMR2 to complete a conversion at a frequency determined by the Timer2 Period.
