Timeout on I2C Write BUSY - not all the time [Adafruit 8x8 matrix backpack]

Surprised about duplicate setup in line 14 in post #7. I think that line should be removed...

Same for the duplicate setup in post #8: line 19 should be removed.

The time killer loops in lines 31..33, 39..41 and 51..53 cause problems because they hog the cpu and nothing else (js-wise) can happen during that time. Wait by burning cycles does not exist / does not work in Espruino... to the contrary, it will break the execution... 'Waiting' has to be done with 'deferred / timed-out resume (w/ setTimeout(...,...); ).

Does the module have a reset command? If so, I would send that before sending the command for turning on the oscillator.

Try something like that - my ugly chained steps with retries on timeouts...

var ini = function() { // first
  require("Font4x6").add(Graphics);
  clearInterval(); // not sure you need that, only w/ arg
  clearWatch(); // not sure you need that, only w/ arg
  // initialisation I2C
  console.log("setup I2C");
  I2C1.setup({scl: B6,sda: B7});
  // pinMode(B6, 'opendrain'); // even though I suggested it, remove it
  /* rajouter les init de connexion pour le display */
  console.log("init programme affichage matrice v2.2 - éric choisy ©2019");
  console.log("mém. utilisée: "+Math.round(process.memory().usage/process.memory().total*100)+"%");
}  
, res = function(tries) { if (tries>0) { // second w/ retries
  try { console.log("reset");
    // I2C1.writeTo(0x70, 0x??); // reset
    setTimeout(osc,250,2);
  } catch(e) { console.log(e);
    setTimeout(res,250,--tries);
  } } else trow "Unable to reset";
}
, osc = function(tries) { if (tries>0) { // third w/ retries
  try { console.log("turn OSC ON");
    I2C1.writeTo(0x70, 0x21); // turn on oscillator
    setTimeout(don,250,2)
  } catch(e) { console.log(e);
    setTimeout(osc,250,--tries);
  } } else trow "Unable to turn osc on";
}
, don = function(tries) { if (tries>0) { // fourth w/ retries
  try { console.log("turn display ON");
    I2C1.writeTo(0x70, 0x81); // display on
    setTimeout(lum,250,2)
  } catch(e) { console.log(e);
    setTimeout(don,250,--tries);
  } } else trow "Unable to turn display ON";
}
, lum = function(tries) { if (tries>0) { // fifth w/ retries
  try { console.log("set brightness");
    I2C1.writeTo(0x70, 0xE0 | 0); // luminosité 0-15
    setTimeout(envoieMatrice, 1000);
  } catch(e) { console.log(e);
    setTimeout(lum,250,--tries);
  } } else throw "Unable to set brightness";
}
;

const onInit = function() {
  ini();
  res(2); // starts the chain \:
};

Another - better looking approach would be nested/chained promises w/ (global) retries that is set / reset at the right spots.

PS: Code not tested (yet)