Arduino for STM32

Posted: **Tue Sep 21, 2021 1:31 pm**

hi, i am trying to use two i2c device simultaneously . Individually single port is function is ok like wise PB7 -SDA , PB6 -SCL or PB11-SDA & PB10 -SCL

when i am scanning first i2c port with just

Wire,begin(); it's giving first device address details ....

When i am scanning second i2c port with

Wire.setSDA(PB11);
Wire.setSCL(PB10);
Wire.begin(); it's giving asecond device address details ....

When i try to use simultaneously - only first device address is coming ..no second device address

Code: Select all

#include <Wire.h>

void setup() {

  Serial.begin(9600);
  Wire.begin();
  
  TwoWire Wire2(PB11,PB10);
  Wire2.begin();
  Serial.println("\nI2C Scanner");
}


void loop() {
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++) {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.

    Wire.beginTransmission(address);
    error = Wire.endTransmission();
    
    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16) 
        Serial.print("0");
      Serial.println(address, HEX);

      nDevices++;
    }
    else if (error == 4) {
      Serial.print("Unknown error at address 0x");
      if (address < 16) 
        Serial.print("0");
      Serial.println(address, HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found");
  else
    Serial.println("done");

  delay(5000);           // wait 5 seconds for next scan
}

Board: blue pill . Core : Stm32 Duino

Posted: **Tue Sep 21, 2021 1:56 pm**

I2C is generally used as a "bus" topology when 2 or more devices are needed:
https://electronics.stackexchange.com/q ... sda-and-a5

If 2 separate I2C embedded controllers are used, two I2C instances are required, but this is really wasteful on SRAM resources as 2 object variables must be in RAM. The consideration is that both devices have different addresses ... some devices can be jumpered to avoid address conflicts.

: I2C.png (6.84 KiB) Viewed 2162 times

Posted: **Thu Sep 23, 2021 10:16 pm**

madhavan wrote: ↑Tue Sep 21, 2021 1:31 pm

Code: Select all

#include <Wire.h>

void setup() {

  Serial.begin(9600);
  Wire.begin();
  
  TwoWire Wire2(PB11,PB10);
  Wire2.begin();
  Serial.println("\nI2C Scanner");
}

It won't work.
You define Wire2 only in setup, and it's not accessible outside setup() function.
You need to define it as a global object.

Code: Select all

#include <Wire.h>
TwoWire Wire2(PB11,PB1);

void setup(){
...
}

Arduino for STM32

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