Serial Communication freezes with BMP180 and Arduino Mega - c++

Question

I recently bought an ELEGO Mega 2560, or in other words an Arduino Mega. I bought a bmp180 sensor as well. I connected the bmp in this fashion, VCC - 3.3v, GND - GND, SCL - 21, SDA - 20. I uploaded a simple code which just displayes altitude. When I go to the Serial Monitor to view the results, nothing pops up. It is suppose to say BMP init success if it connects, and fail if it doesn't. When I go to the monitor, it just doens't say anything. When I disconnect the sensor, it says fail. It appears as if the Serial Monitor just freezes. Also a headsup, my code is very messy, I'm sorry if it's hard to keep up.
#include <Wire.h>
#include <SFE_BMP180.h>
SFE_BMP180 bmp180;
float Po = 1014.9;
#define ledPin 7
#define TransmitPin 5
//int Altitude = 5;
int sendValue;
String incomingString;
unsigned long lastTransmission;
const int interval = 1000;
void setup() {
Wire.begin();
pinMode(ledPin, OUTPUT);
pinMode(2, INPUT);
pinMode(10, OUTPUT);
pinMode(TransmitPin, OUTPUT);
bool success = bmp180.begin();
Serial.begin(115200);
if (success) {
Serial.println("BMP180 init success");
}
else
Serial.println("fail");
}
void loop() {
sendValue = digitalRead(29);
if (sendValue == HIGH) {
if (millis() > lastTransmission + interval) {
Serial.println("AT+SEND=1,8,Return");
digitalWrite(TransmitPin, HIGH);
delay(100);
digitalWrite(TransmitPin, LOW);
lastTransmission = millis();
}
}
if (Serial.available()) {
incomingString = Serial.readString();
if (incomingString.indexOf("Testing!") > 0) {
digitalWrite(10, HIGH);
delay(100);
digitalWrite(10, LOW);
}
}
char status;
double T, P, alt;
bool success = false;
status = bmp180.startTemperature();
if (status != 0) {
delay(1000);
status = bmp180.getTemperature(T);
if (status != 0) {
status = bmp180.startPressure(3);
if (status != 0) {
delay(status);
status = bmp180.getPressure(P, T);
if (status != 0) {
if (millis() > lastTransmission + interval) {
alt = bmp180.altitude(P, Po);
Serial.print("AT+SEND=1,8,");
int altAsFoot = alt * 3.281;
Serial.println(altAsFoot);
digitalWrite(TransmitPin, HIGH);
delay(100);
digitalWrite(TransmitPin, LOW);
}
for (int i = 0; i < 1800; i++) {
delay(1);
if (Serial.available()) {
incomingString = Serial.readString();
if (incomingString.indexOf("+OK") > 0) {
digitalWrite(ledPin, HIGH);
delay(100);
digitalWrite(ledPin, LOW);
}
if (incomingString.indexOf("Testing!") > 0) {
digitalWrite(10, HIGH);
delay(100);
digitalWrite(10, LOW);
}
}
}
}
}
}
}
}

Answer 1

Turns out it was a hardware issue. I had ground shorted to SDA. I'm assuming the same will happen if it's shorted to SCL. Make sure both SDA and SCL aren't shorted to each other or ground.