Teensy 3.6 Wire library question

[heesups]

Hello,

My project is to read multiple slave microcontrollers' data (up to 8 microcontrollers, 16 Bytes per each) using one master microcontroller.
In the case of the slave microcontrollers, each slave reads 4 sensors data and the sampling rate of all four sensors' data is 40 Hz. Also, I have to use ATmega328P as a slave microcontroller.
My code was working fine when I used an Arduino Uno as a master. However, if I run the same code on Teensy 3.6, the code did not work.

One thing I have figured out is that on the contrary to Arduino, once Teensy is used as a master it can't be used as a slave.
In other words, once Wire.beginTransmission(), Wire.write(), Wire.endTransmission() are used in Teensy, Wire.onReceive doesn't work at all.
For example, in the below code, if I made "sendEvent(42);" as a comment, a master Teensy received data well from a slave ATmega328P.
However, if "sendEvent" function is used, the Teensy can't receive data from a slave.

#include <Wire.h>
#define num 4 //number of slaves
#define reqbyte 16 // Bytes to be requested to slaves
// flag
byte stat = 0;
const byte to_slave = 1;
volatile byte from_slave = 0;
// I2C Address
#define MY_ADDRESS 25
#define SLAVE_ADDRESS 42;

void setup()
{ 
  while (!Serial);
  delay(1000);
  
  Serial.begin(115200);  
  delay(15);
 
  Wire.begin(MY_ADDRESS);     // Join I2C bus with address "MY_ADDRESS"
  delay(100);
  // Initialize communication between slaves
  Wire.onReceive(receiveEvent); // register event
  //sendEvent(42); // Initialize the first slave uC
  Serial.println("********START!*********");   
}

void loop()
{
}
///////////////////////////// Functions ////////////////////////////////////////
void sendEvent(const byte ADDRESS){
  Wire.beginTransmission (ADDRESS);
  Wire.write (to_slave);
  Wire.endTransmission ();
}

void receiveEvent(int howMany)
 {
  from_slave = Wire.read(); //received event
  Serial.print(from_slave);
  Serial.println("Works!");   
 }

#include <Wire.h>

// I2C Address
#define MY_ADDRESS 42
#define OTHER_ADDRESS 25

// Slave status
volatile boolean stat = false;
// Send & receive event
const byte from_master = 1;
const byte to_master = 1; //should assign a unique number to each slave
//////////////////////////////////////////////////////////////////////////////////////////////////
void setup()
{
  while (!Serial);
  delay(1000);
  
  Serial.begin(115200); // set up baud rate for serial 
  delay(15);

  Wire.begin(MY_ADDRESS);  // Activate I2C network
  Wire.onReceive(receiveEvent); // interrupt handler for when data is wanted
}

void loop() {
sendEvent(OTHER_ADDRESS);
delay(100);
}
///////////////////////////// Functions ////////////////////////////////////////
void sendEvent(const byte ADDRESS){
  Wire.beginTransmission (ADDRESS);
  Wire.write (to_master);
  Wire.endTransmission ();
}

void receiveEvent()
 {
  byte c = Wire.read(); //received event
  if (c == from_master){ 
  stat = true;
  }
  else {}
 }

This is a bit critical because, in my code, a slave sends a byte to a master to set a flag to let the master know that 16 bytes data is ready to be transmitted.
Is there a way to make Wire.onReceive functional in a master Teensy?

 

[PaulStoffregen]

No, I'm sorry, this isn't supported. Teensy's Wire library supports master only and slave only modes, but not mixing the 2 modes.

I'll put this on my list of features to improve for the future. But I'm afraid the timeframe for supporting both modes is likely a very long way out.

 

[KurtE]

You might also look at the i2c_t3 library to see if it has the slave support you are looking for.