arduino programming: not enough memory message - memory

Question

I am new to arduino programming (Arduino Pro Mini 3.3v version), i have some code like below. I am connecting 9DOF, OLED screen and a BLE breakout to arduino pro mini.
I already went through some of the memory optimization tips, but i still have some issue. Even with the following code, i only have 9 bytes left for dynamic memory. If i enable BTLEserial.begin();, it will kill the memory. Please any suggestions will be appreciated.
#include <Wire.h>
#include <SPI.h>
#include <SparkFunLSM9DS1.h>
#include "Adafruit_BLE_UART.h"
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);
LSM9DS1 imu;
#define LSM9DS1_M 0x1E // Would be 0x1C if SDO_M is LOW
#define LSM9DS1_AG 0x6B // Would be 0x6A if SDO_AG is LOW
#define ADAFRUITBLE_REQ 10
#define ADAFRUITBLE_RDY 2
#define ADAFRUITBLE_RST 9
Adafruit_BLE_UART BTLEserial = Adafruit_BLE_UART(ADAFRUITBLE_REQ, ADAFRUITBLE_RDY, ADAFRUITBLE_RST);
void setup(void) {
Serial.begin(9600);
display.begin(SSD1306_SWITCHCAPVCC, 0x3D); // initialize with the I2C addr 0x3D (for the 128x64)
display.display();
delay(2000);
display.clearDisplay();
display.drawPixel(10, 10, WHITE);
display.display();
delay(2000);
display.clearDisplay();
imu.settings.device.commInterface = IMU_MODE_I2C;
imu.settings.device.mAddress = LSM9DS1_M;
imu.settings.device.agAddress = LSM9DS1_AG;
if (!imu.begin())
{
while (1)
;
}
// BTLEserial.begin(); - if i uncomment this code, i will get a not enough memory error.
}
aci_evt_opcode_t laststatus = ACI_EVT_DISCONNECTED;
void loop() {
displayAllDOF();
}
void displayAllDOF(){
display.setTextSize(1);
display.setTextColor(WHITE);
imu.readGyro();
display.setCursor(0,0);
display.print("G:");
display.print(imu.calcGyro(imu.gx));
display.print(", ");
display.print(imu.calcGyro(imu.gy));
display.print(", ");
display.print(imu.calcGyro(imu.gz));
display.println(" ");
imu.readAccel();
display.print("A:");
display.print(imu.calcAccel(imu.ax));
display.print(", ");
display.print(imu.calcAccel(imu.ay));
display.print(", ");
display.print(imu.calcAccel(imu.az));
display.println(" ");
imu.readMag();
display.print("M:");
display.print(imu.calcMag(imu.mx));
display.print(", ");
display.print(imu.calcMag(imu.my));
display.print(", ");
display.print(imu.calcMag(imu.mz));
display.println(" ");
display.display();
display.clearDisplay();
}

Answer 1

To start, you'll need to figure out where your RAM is going - How much does each library take? Do you really need to run them all at the same time? You know that you can run the display library, and the IMU code in your current setup - Can you implement something that only enables the IMU code, pulls data, then disables it? And the same with the display and BTLE code? That way each library is only consuming RAM when it's needed, and frees it once it's operation is finished
Update 1
An example of what I mentioned above. I do not know if all the libraries implement the .end() function. They may have a similar method you can use.
// Simple data storage for the .gx and .gy values
typedef struct {
float x, y;
} GyroData_t;
GyroData_t getImuData() {
GyroData_t data;
// Create the IMU class, gather data from it, and then destroy it
LSM9DS1 *imu = new LSM9DS1();
imu->begin();
imu->readGyro();
data.x = imu.gx;
data.y = imu.gy;
imu->end();
// This will reclaim the RAM that was used by the IMU - We no longer need it
delete imu;
return data;
}
void displayAllDOF() {
// Gather the IMU data
GyroData_t data = getImuData();
// Create the display object, and print the data we received
Adafruit_SSD1306 *display = new Adafruit_SSD1306(OLED_RESET);
display->print(...);
....
display->end();
// Reclaim the display RAM used
delete display;
// Do any bluetooth operations now
doBluetoothStuff();
}
void doBluetoothStuff() {
Adafruit_BLE_UART *BTLEserial = new Adafruit_BLE_UART(ADAFRUITBLE_REQ, ADAFRUITBLE_RDY, ADAFRUITBLE_RST);
BTLESerial->begin();
...
BTLESerial->end();
delete BTLESerial;
}