I am working on a drone project that uses an MPU6050 and BMP280 for an Arduino flight controller. Both are running on I2C protocol; the MPU is being called with the Wire library and the BMP is using the Adafruit_BMP280_Library.
The flight controller runs on a loop of 4 ms so I am trying to make the sensors run fast. Before I added the BMP chip, the MPU6050 was running a cycle in around 600ms. When I set up the BMP chip, the MPU run time jumped to 1700ms. Does anyone know why the time is increasing?
Here is the test code I have been using:
void setup(){
Serial.begin(57600);
Serial.println("Starting up.");
Wire.begin();
Wire.setClock(400000);
calibrate_barometer();
set_gyro_registers();
calibrate_gyro();
}
void loop(){
run_gyro();
}
Setting up the BMP sensor:
void calibrate_barometer() {
//Setup the bmp280 chip
//Begin connection with the BMP280 chip
bmp.begin();//Begin connection with the BMP280 chip
//Configure the BMP280 sampling settings. This will only be used to calculate the calibration values.
bmp.setSampling(Adafruit_BMP280::MODE_NORMAL, // Operating Mode.
Adafruit_BMP280::SAMPLING_X2, // Temp. oversampling
Adafruit_BMP280::SAMPLING_X16, // Pressure oversampling
Adafruit_BMP280::FILTER_X16, // Filtering
Adafruit_BMP280::STANDBY_MS_1); // Standby time set to 0.5 ms
//Let's take multiple pressure data samples on the ground so that we can determine the average base pressure reading (calibration).
Serial.println("bmp280 ready");
for (int cal_int = 0; cal_int < 2000 ; cal_int ++){
altitude_cal += bmp.readPressure();
}
altitude_cal /= 200000; //Divide by number of cycles * 100 to get to the correct units
Serial.print("Alt cal: ");
Serial.println(altitude_cal);
Serial.println(bmp.readAltitude(altitude_cal));
Serial.println("bmp280 ready");
}
Setting up and running the MPU sensor
void set_gyro_registers(){
//Setup the MPU-6050
if(eeprom_data[31] == 1){
Wire.beginTransmission(gyro_address); //Start communication with the address found during search.
Wire.write(0x6B); //We want to write to the PWR_MGMT_1 register (6B hex)
Wire.write(0x00); //Set the register bits as 00000000 to activate the gyro
Wire.endTransmission(); //End the transmission with the gyro.
Wire.beginTransmission(gyro_address); //Start communication with the address found during search.
Wire.write(0x1B); //We want to write to the GYRO_CONFIG register (1B hex)
Wire.write(0x08); //Set the register bits as 00001000 (500dps full scale)
Wire.endTransmission(); //End the transmission with the gyro
Wire.beginTransmission(gyro_address); //Start communication with the address found during search.
Wire.write(0x1C); //We want to write to the ACCEL_CONFIG register (1A hex)
Wire.write(0x10); //Set the register bits as 00010000 (+/- 8g full scale range)
Wire.endTransmission(); //End the transmission with the gyro
//Let's perform a random register check to see if the values are written correct
Wire.beginTransmission(gyro_address); //Start communication with the address found during search
Wire.write(0x1B); //Start reading @ register 0x1B
Wire.endTransmission(); //End the transmission
Wire.requestFrom(gyro_address, 1); //Request 1 bytes from the gyro
while(Wire.available() < 1); //Wait until the 6 bytes are received
if(Wire.read() != 0x08){ //Check if the value is 0x08
digitalWrite(12,HIGH); //Turn on the warning led
while(1)delay(10); //Stay in this loop for ever
}
Wire.beginTransmission(gyro_address); //Start communication with the address found during search
Wire.write(0x1A); //We want to write to the CONFIG register (1A hex)
Wire.write(0x03); //Set the register bits as 00000011 (Set Digital Low Pass Filter to ~43Hz)
Wire.endTransmission(); //End the transmission with the gyro
}
}
// Getting the cal offsets for the sensor
void calibrate_gyro(void) {
//Let's take multiple gyro data samples so we can determine the average gyro offset (calibration).
for (cal_int = 0; cal_int < 2000 ; cal_int ++){
if(cal_int % 15 == 0)digitalWrite(12, !digitalRead(12));
gyro_signalen();
gyro_pitch_cal += gyro_pitch;
gyro_roll_cal += gyro_roll;
gyro_yaw_cal += gyro_yaw;
angle_pitch_acc_cal += acc_x;
angle_roll_acc_cal += acc_y;
//We don't want the esc's to be beeping annoyingly. So let's give them a 1000us puls while calibrating the gyro.
PORTB |= B00001111;
delayMicroseconds(1000);
PORTB &= B11110000;
delay(3);
}
gyro_pitch_cal /= 2000;
gyro_roll_cal /= 2000;
gyro_yaw_cal /= 2000;
angle_pitch_acc_cal /= 2000;
angle_roll_acc_cal /= 2000;
}
void run_gyro(){
//Read the MPU-6050
test_timer = micros();
Wire.beginTransmission(gyro_address); //Start communication with the gyro.
Wire.write(0x3B); //Start reading @ register 43h and auto increment with every read.
Wire.endTransmission(); //End the transmission.
Wire.requestFrom(gyro_address,14); //Request 14 bytes from the gyro.
while(Wire.available() < 14); //Wait until the 14 bytes are received.
acc_x = Wire.read()<<8|Wire.read(); //Add the low and high byte to the acc_x variable.
acc_y = Wire.read()<<8|Wire.read(); //Add the low and high byte to the acc_y variable.
acc_z = Wire.read()<<8|Wire.read(); //Add the low and high byte to the acc_z variable.
temperature = Wire.read()<<8|Wire.read(); //Add the low and high byte to the temperature variable.
gyro_pitch = Wire.read()<<8|Wire.read(); //Read high and low part of the angular data.
gyro_roll = Wire.read()<<8|Wire.read(); //Read high and low part of the angular data.
gyro_yaw = Wire.read()<<8|Wire.read(); //Read high and low part of the angular data.
acc_z *= -1; //Invert acc_z
gyro_yaw *= -1; //Invert gyro_yaw
//Compensate for gyro offsets once the calibration has been completed.
if(cal_int == 2000){
gyro_pitch -= gyro_pitch_cal; //Only compensate after the calibration.
gyro_roll -= gyro_roll_cal; //Only compensate after the calibration.
gyro_yaw -= gyro_yaw_cal; //Only compensate after the calibration.
}
Serial.println(micros() - test_timer);
}