STM32: Cheap and Powerful

Four times more powerful than the Arduino Mega, today I continue the discussion concerning the STM32 Maple Mini. I’m a big fan of this, as it is an Arm chip and (even better) supports Arduino IDE. Thus, I program this microcontroller as if it were an Arduino. However, the STM32 is much more powerful.

STM32 Maple Mini can be find in this link:http://s.click.aliexpress.com/e/uV7QZBI

We made an assembly with a sensor, this time the BMP180. Added to this is a 1.8 "TFT Display, 160 pixels by 128, which I consider a lot for a device of this size.

In today's video, we’ll read the temperature and pressure values using the BMP180, display the read data on the display, and log this read data into a file on the SD card.

Check out the Maple Mini pinout which, in addition to being incredible because it has many doors, is relatively cheap, because its SMT core costs only a few cents.

In our assembly, we have an STM32 Maple Mini connected via i2c port to a BMP180, which is a temperature and pressure sensor. The circuit is powered by the USB port. We determined the temperature data printing in red and the pressure in blue.

Look for Adafruit Unified Sensor and install Adafruit Unified Sensor.

Go to https://github.com/KenjutsuGH/Adafruit-ST7735-Library

and download the zip.

Unzip the file and place it in the Documents / Arduino / libraries folder

Look for BMP085 and install Adafruit BMP085 Library.

Look for BMP085 and install Adafruit BMP085 Library.

First, we import libs from the display, text source, sensor, communication, and SD card. We have defined the settings we use in the display assembly and the SD pin.

//Importamos as libs do display, fonte do texto, 
//sensor, comunicação e cartão SD
#include <Adafruit_GFX_AS.h>
#include <Adafruit_ST7735.h>
#include <Fonts/FreeSans9pt7b.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP085.h>
#include <SPI.h>
#include <Wire.h>
#include <SD.h>
 
//Configuração que usamos na montagem
//do display
#define DISPLAY_CS     PA2
#define DISPLAY_RST    PA4
#define DISPLAY_DC     PA3
 
//Pino CS que o SD está ligado
#define SD_CS     PA8
 
#define ROW_SIZE 18
#define DISPLAY_WIDTH 160
#define LEFT_MARGIN 9
 
//Objeto responsável pelo display
Adafruit_ST7735 display = Adafruit_ST7735(DISPLAY_CS,  DISPLAY_DC, DISPLAY_RST);
 
//Objeto responsável pelo sensor
Adafruit_BMP085 bmp;

We initialize the sensor, the SD, and the display, and then define the formatting of this screen.

void setup() {
  Serial.begin(115200);
 
  //Inicializa o sensor
  if (!bmp.begin()) {  
    Serial.println("Não achou o sensor BMP, verifique a montagem");
  }
 
  //Inicializa o SD
  if (!SD.begin(SD_CS)) {
    Serial.println("Erro ao inicializar lib SD!");
  }
 
  //Inicializa o display
  display.initR(INITR_BLACKTAB);
  //Rotaciona o conteúdo mostrado
  display.setRotation(1);
  //Configura a fonte do texto
  display.setFont(&FreeSans9pt7b);
  //Pinta a tela de branco
  display.fillScreen(ST7735_WHITE);
  //Configura e mostra o texto da temperatura
  display.setCursor(LEFT_MARGIN, 1*ROW_SIZE);
  display.setTextColor(ST7735_RED);
  display.print("Temperature:");
  //Configura e mostra o texto da pressão
  display.setCursor(LEFT_MARGIN, 4*ROW_SIZE);
  display.setTextColor(ST7735_BLUE);
  display.print("Pressure:");
}

We start the Loop with the reading of the temperature, going to pressure, and point to the Strings that will be displayed on the display and recorded in the log.

void loop() {
  //Faz a leitura da temperatura
  float temperature = bmp.readTemperature();
 
  //Faz a leitura da pressão
  int pressure = bmp.readPressure();
 
  //Strings que serão exibidas no display e gravadas no log
  String strTemp = String(temperature) + "C";
  String strPress = String(pressure) + "Pa";

Next, we define new formatting of the display.

//Limpa o texto da temperatura anterior
  display.fillRect(0, 1*ROW_SIZE + 2, DISPLAY_WIDTH, ROW_SIZE, ST7735_WHITE);
  //Posiciona o cursor no local correto
  display.setCursor(LEFT_MARGIN, 2*ROW_SIZE);
  //Configura a cor do texto como vermelho
  display.setTextColor(ST7735_RED);
  //Mostra a String da temperatura
  display.println(strTemp);
  //Limpa o texto da pressão anterior
  display.fillRect(0, 4*ROW_SIZE + 2, DISPLAY_WIDTH, ROW_SIZE, ST7735_WHITE);
  //Posiciona o cursor no local correto
  display.setCursor(LEFT_MARGIN, 5*ROW_SIZE);
  //Configura a cor do texto como azul
  display.setTextColor(ST7735_BLUE);
  //Mostra a String da pressão
  display.println(strPress);

Finally, we open the log file for writing and determine the behavior as needed.

//Abre o arquivo de log para escrita
  File dataFile = SD.open("log.txt", FILE_WRITE);
   
  //Se conseguiu abrir o arquivo
  if (dataFile) {
    //Escreve a String da temperatura
    dataFile.println(strTemp);
    //Escreve a String de pressão
    dataFile.println(strPress);
    //Fecha o arquivo
    dataFile.close();
  }
 
  //Espera 5 segundos
  delay(5000);
}

Download the files:

PDF

INO