Hacking ESP32 - multiplexing I2C

• Multiple devices with the same I2C address? 
• Don't like bit-banging? 
• No money for extra I2C multiplexer? 
• Spare IO ports ? 

==> Continue reading !

This was a short proof of concept to use the IO_MUX capability of the ESP32 to change online the PINs used for the I2C communication. Basically, the I2C  hardware module can be connected to nearly every pin ofd the ESP32 and this switch can be done on the fly. I was not sure how good this work but a fast breadboard build and software sketch showed that it works like charme! See the picture and the code snippet below. Combining this with this nice hack to use only one SCL or SDA  for multiple devices (link), this could be even more advantagous in several cases and save costs/space for an I2C multiplexer!

Picture of the breadboard setup:

The code snippet running on the ESP32:

// ESP32 S3 Dataseeht (as example) https://www.elecrow.com/download/product/DLC35010R/esp32-s3_datasheet_en.pdf
// Example i2c driver: https://github.com/espressif/esp-idf/blob/master/components/driver/i2c/i2c.c

#include <Wire.h>
#include "C:\Users\pagantroll\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.12\tools\sdk\esp32c3\include\driver\include\driver\i2c.h"
#include "C:\Users\pagantroll\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.12\tools\sdk\esp32\include\esp_rom\include\esp_rom_gpio.h"

#include <DFRobot_QMC5883.h>
DFRobot_QMC5883 compass(&Wire, QMC5883_ADDRESS );

#define I2C_SDA1 3 
#define I2C_SCL1 4
#define I2C_SDA2 1 
#define I2C_SCL2 2

void activate_I2C_GPIO_a() {
  i2c_set_pin(0, I2C_SDA1,I2C_SCL1, GPIO_PULLUP_ENABLE,GPIO_PULLUP_ENABLE,I2C_MODE_MASTER);
  esp_rom_gpio_connect_out_signal(I2C_SCL2, SIG_GPIO_OUT_IDX, false, false);
  esp_rom_gpio_connect_out_signal(I2C_SDA2, SIG_GPIO_OUT_IDX, false, false);
}

void activate_I2C_GPIO_b() {
  i2c_set_pin(0, I2C_SDA2,I2C_SCL2, GPIO_PULLUP_ENABLE,GPIO_PULLUP_ENABLE,I2C_MODE_MASTER);
  esp_rom_gpio_connect_out_signal(I2C_SCL1, SIG_GPIO_OUT_IDX, false, false);
  esp_rom_gpio_connect_out_signal(I2C_SDA1, SIG_GPIO_OUT_IDX, false, false);
}

void readMagSensor() {
  sVector_t mag = compass.readRaw();
  Serial.print(mag.XAxis);Serial.print(",");
  Serial.print(mag.YAxis);Serial.print(",");
  Serial.print(mag.ZAxis);Serial.print(",");
}


void setup() {

  Serial.begin(115200);  
  Serial.println("Tesing I2C Multiplexing");
  
  Wire.begin(I2C_SDA1, I2C_SCL1);

  activate_I2C_GPIO_a();
  while (!compass.begin()) {
    Serial.println("Could not find a valid 5883 sensor on first port, check wiring!");
    delay(500);
  } Serial.println("First sensor initialized");

  activate_I2C_GPIO_b();
  while (!compass.begin()) {
    Serial.println("Could not find a valid 5883 sensor on second port, check wiring!");
    delay(500);
  } Serial.println("Second sensor initialized");

}


void loop() {
  delay(20);

  activate_I2C_GPIO_a();
  readMagSensor();    

  activate_I2C_GPIO_b();
  readMagSensor();    

  Serial.println("");
}

P.S.: Also thanks to the ESP forum (link) who gave me very fast advice!

P.S.: Here the results with a common SCL line and only two seperate SDA lines. Works comparable nice :-)

6D Mouse DIY Link List

See the officale page I am maintening right now: link

The professional product tear down: link or link or link 

And here are all know DIY projects (only full 6D in this list)

Project Name	Author	link	Picture	Detection / Electronics	Mechanics
OS3M Mouse	colton.baldridge	link		inductance to digital sensors for distance to w/ metal object as Stewart platform	3D print (included printed spring mechanism)
Shamrock Sixnav	Brian Lu (GreenCap)	link		IR LED + Phototransistor 3D print with variable thickness (damping of IR light by displacement) 3x X/Y detectionin 120° setting	3D Printing + Springs
Space Mushroom	shiura	link1 link_video		Stewart platform made from potentiometers (3x 2D analog joysticks)	3D printed
spacefox	Pepijn de Vos	link1 link_video		Stewart platform made from potentiometers.	3D prints & cuts from triplex
6D (axsotic)	valentin heun	link
Simple  6D Space Mouse	Bastel Baus	link		linear hall sensors	3D printed with metal spring