I2C between Trinkets and Mega not working

Projects Programming
1

here is my dilemma...FIRST - what i am trying to do:

I have 2 trinkets and a mega 1280 (i know the schematic says 2560...but it doesn't have my model) talking via I2C...i have the master trinket 5V take input from a button...when pressed it is supposed light the LED connected to it and send a "1" to the 2 slaves...when you let go it sends a "0"...the slave trinket 3.3V waits for message...when receiving a 1 it turns on the led...a 0 turns is off...the mega does the opposite...0 turns it on the led and 1 turns it off.

what i have got working:

Trinket to Trinket I2C is working fine...where my issue comes into play is when i add in the mega...so i tried just trinket to mega...still a no go...so is there something i am doing wrong on the mega side??? the trinkets and the 4 bit level shifter are brand new from adafruit...the mega i have had for a while and have used to talk to other megas...i have attached code and schematic.

Trinket Master code

#include <TinyWireM.h>
#define SWITCH 3
#define LED 4
void setup()
{
  TinyWireM.begin();
  pinMode(LED, OUTPUT);
  pinMode(SWITCH, INPUT);
  digitalWrite(SWITCH, HIGH);
}

void loop()
{
  if (! digitalRead(SWITCH)) {
    digitalWrite(LED, HIGH);
    TinyWireM.beginTransmission(4);
    TinyWireM.send(1);
    TinyWireM.endTransmission();
    TinyWireM.beginTransmission(5);
    TinyWireM.send(1);
    TinyWireM.endTransmission();
  } 
  else {
    digitalWrite(LED, LOW);
    TinyWireM.beginTransmission(4);
    TinyWireM.send(0);
    TinyWireM.endTransmission();
    TinyWireM.beginTransmission(5);
    TinyWireM.send(0);
    TinyWireM.endTransmission();
  }
}

Trinket Slave code

#include <TinyWireS.h>

void setup()
{
  TinyWireS.begin(4);
  pinMode(3, OUTPUT);
  digitalWrite(3, LOW);
}

void loop()
{
  while(0 < TinyWireS.available())
  {
    if (TinyWireS.receive() == 1) {    
      digitalWrite(3, HIGH);
    }
    else {    
      digitalWrite(3, LOW);
    }
  }
}

Mega Slave code

#include <Wire.h>

void setup() {
  Wire.begin(5);
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  Wire.onReceive(receiveEvent);
  Serial.begin(9600);
}

void loop() {
}

void receiveEvent(int howMany)
{
  while(0 < Wire.available())
  {
    byte c = Wire.read();
    Serial.println(c);
    if (0 == c) {    
      digitalWrite(13, HIGH);
    }
    else {    
      digitalWrite(13, LOW); 
    }  
  }
}

i2c-trinket-trinket-mega_schem.jpg
i2c-trinket-trinket-mega_schem.jpg2442×2667 271 KB

2

I didn't know WIRE and TinyWire protocols were compatible. I thought the ATtiny85 could not read WIRE and the Mega could not
read TinyWire. If they can I would like to know because then I can do the same thing with my UNO and my ATtiny85's .

3

from what i read...they are both I2C...and the TinyWire can read and write other I2C components...so i don't see why it wouldn't...but when i add the mega in the mix... i locks the trinkets...so i have no clue what is going on...i seen a vid of someone who is doing it here

4

vid not much help

5

i agree...doesn't show much...but the links say that it works

6

Did you do the schematic ? If so , what software ?

7

are you sure this is right ?

 while(0 < Wire.available())
  {
    byte c = Wire.read();
    Serial.println(c);
    if (0 == c) {             
      digitalWrite(13, HIGH);
    }
    else {    
      digitalWrite(13, LOW); 
    }  
  }

ARE YOU SURE IT SHOULDN'T BE if(c==0) ?

8

i did the schematic in Fritzing...it is easy to do there...and it doesn't matter which side the constant is on

int c = 3;
if (c == 3) {Serial.println("true");}else{Serial.println("false");}
if (3 == c) {Serial.println("true");}else{Serial.println("false");}

they will both return true...my issue happen only after connecting the mega...BUT...i got it to work...i took the code in the receiveEvent and put it in the loop...YAYAYAYAYAY

9

Can you post the corrected code ? (for the Mega)

10

SURE...i am also going to make a more detailed video on how to do this

#include <Wire.h>

void setup() {
  Wire.begin(5);
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  Wire.onReceive(receiveEvent);
  Serial.begin(9600);
}

void loop() {
    while(0 < Wire.available())
  {
    byte c = Wire.read();
    Serial.println(c);
    if (0 == c) {    
      digitalWrite(13, HIGH);
    }
    else {    
      digitalWrite(13, LOW); 
    }  
  }
}
11 
  #include <Wire.h>

void setup() {
  Wire.begin(5);
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  Wire.onReceive(receiveEvent);
  Serial.begin(9600);
}

void loop() {
}

void receiveEvent(int howMany)
{
  while(0 < Wire.available())
  {
    byte c = Wire.read();
    Serial.println(c);
    if (0 == c) {    
      digitalWrite(13, HIGH);
    }
    else {    
      digitalWrite(13, LOW); 
    }  
  }
}

/////////////////////////////-- CORRECTED ---////////////////////////////////////////

  #include <Wire.h>

void setup() {
  Wire.begin(5);
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  Wire.onReceive(receiveEvent);
  Serial.begin(9600);
}

void loop() {
    while(0 < Wire.available())
  {
    byte c = Wire.read();
    Serial.println(c);
    if (0 == c) {    
      digitalWrite(13, HIGH);
    }
    else {    
      digitalWrite(13, LOW); 
    }  
  }
}

I'm having a hard time finding the difference between your original Mega code and the corrected one you just posted.
Can you label the part you added so it is easier to see ?

12
13

Where's the link for Part-2 (both of the links are the same)

14

i am going to make part 2 tomorrow

15

I'm such an idiot. I didn't realize that was you doing the video. I thought you were posting the link for me to look at to answer my question until I read your last post. Nice vid ! That came out good.

16

thanks...i wanted to make something more than the others...but i didn't want to take 15 mins to explain how to hook everything up...part 1 is mostly for people who know I2C...but need to know how to link 5v and 3.3v devices together...part 2 will re-explain the I2C for arduino's and teach you it for the trinkets

17

Check out this video I did of a Police Car LED simulator that I made from a Scargill Youtube I saw. It's an ATtiny85 and four leds
two red and two blue.

18

Look at your schematic.
Level shifter LV input 3 not connected , HV 3 connected
LV input 4 connected HV 4 not connected

How does that work ?

Also, you don't show any current limiting resistors for the leds . Why ? (should be 220 ohms)
Why are there no 4.7k pullup resistors on SDA & SCL ? That's a standard requirement. I2C backpacks and lcds have them built in but when you DIY you have to include them to keep the bus stable and biased correctly.

I forgot to ask, does it matter what clock frequency the ATtiny85 is set for in the boards.txt file ? (will 1 Mhz work ?)

19

I programmed the chips and wired up the circuit and it's not working . I can't even get the leds to toggle.
Can you repost the working code for all three ?
The attached files are the code I am running (UNO instead of Mega)

MEGA_SLAVE.ino (409 Bytes)

TRINKET_MASTER.ino (665 Bytes)

TRINKET_SLAVE.ino (295 Bytes)

20

ARE YOU SURE IT SHOULDN'T BE if(c==0) ?

if ( 0 == c )

is perfectly valid, and is recommended practise by some experts. Possibly, the same experts who recommend ++i instead of i++, for no good reason in 99.9% of usages.

The ostensible reason for writing this way, is that if you write ( by mistake )

if ( 0 = c )

you will get a compilation error.

But if you write ( also by mistake )

if ( c = 0 )

then you won't get a compilation error, you will get a bug which sometimes may be very difficult to track down.