How to get GPS Data when switch is pressed in Atmega328p - c

Question

So I am working on getting the gps data when the button is pressed using external interrupt. My problem is , it is working without the external interrupt but when I added it, it's not getting the data. Is something wrong with my code? I am using quectel l80-m39 for gps connected to the rx of atmega328p. Provided below is my code. The button is connected to PD3 of atmega.
#define F_CPU 8000000UL // Defining the CPU Frequency
#include <avr/io.h> // Contains all the I/O Register Macros
#include <util/delay.h> // Generates a Blocking Delay
#include <avr/interrupt.h>
#define USART_BAUDRATE 9600 // Desired Baud Rate
#define BAUD_PRESCALER (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
void USART_Init()
{
// Set Baud Rate
UBRR0H = (unsigned char)(BAUD_PRESCALER >> 8);
UBRR0L = (unsigned char)BAUD_PRESCALER;
// Enable Receiver
UCSR0B |= (1 << RXEN0);
// Set data frame format: asynchronous mode,no parity, 1 stop bit, 8 bit size
UCSR0C |= (1 << UCSZ01) | (1 << UCSZ00);
}
unsigned char USART_ReceivePolling(void)
{
while (!(UCSR0A & (1 << RXC0)));
return UDR0;
}
void readgps()
{
uint8_t lati_value[15];
unsigned char LocalData;
int i = 0;
LocalData = USART_ReceivePolling();
if (LocalData == '$')
{
LocalData = USART_ReceivePolling();
if (LocalData == 'G')
{
LocalData = USART_ReceivePolling();
if (LocalData == 'P')
{
LocalData = USART_ReceivePolling();
if (LocalData == 'G')
{
LocalData = USART_ReceivePolling();
if (LocalData == 'G')
{
LocalData = USART_ReceivePolling();
if (LocalData == 'A')
{
LocalData = USART_ReceivePolling();
if (LocalData == ',')
{
LocalData = USART_ReceivePolling();
while (LocalData != ',')
{
LocalData = USART_ReceivePolling();
}
LocalData = USART_ReceivePolling();
while (LocalData != ',')
{
lati_value[i] = LocalData;
++i;
LocalData = USART_ReceivePolling();
}
PORTD |= (1 << PD2);
_delay_ms(100);
}
}
}
}
}
}
} else
{
PORTD &= ~(1 << PD2);
}
}
int main(void)
{
EICRA |= (1 << ISC10) | (1 << ISC11); // interrupt on rising edge of INT1
EIMSK |= (1 << INT1); // external interrupt enable on INT1
sei();
while (1)
{
}
}
ISR(INT1_vect)
{
if (PIND & (1 << 3))
{
DDRD = 0b01110110;
USART_Init();
readgps();
}
}

Answer 1

USART_ReceivePolling() is blocking the ISR. You should never block the ISR. In the ISR just set a flag and check it in the main loop. Something like this (unchanged code removed):
// ...
// Flag for reading the GPS
volatile unsigned char g_read_gps = 0;
// ...
int main(void)
{
// ...
while (1)
{
if (g_read_gps) {
readgps();
g_read_gps = 0;
}
}
}
ISR(INT1_vect)
{
if (PIND & (1 << 3))
{
g_read_gps = 1;
}
}