i2c newb questions

Hi, I ported PCA9865 functions over. I am trying to access it on the STM32F4Discovery. I am getting timeouts on both B6,B7 and B8,B9 pins. On B6,B7 I get
INTERNAL ERROR: Timeout on I2C Write BUSY
INTERNAL ERROR: Timeout on I2C Write SB
INTERNAL ERROR: Timeout on I2C Write Transmit Mode 2
INTERNAL ERROR: Timeout on I2C Write Transmit
INTERNAL ERROR: Timeout on I2C Write Transmit
at line 5 col 48
this.i2c.writeTo(this.a, [PCA9685_MODE1, 0x0]);

on B8,B9
INTERNAL ERROR: Timeout on I2C Write Transmit Mode 2
INTERNAL ERROR: Timeout on I2C Write Transmit
INTERNAL ERROR: Timeout on I2C Write Transmit
at line 5 col 48
this.i2c.writeTo(this.a, [PCA9685_MODE1, 0x0]);

Any advice on debugging?

Did you remember to do the I2C setup()?

Is it wired up correctly? If you aren't using a breakout board, you need to have the 10k pullups (these are included in I2C breakout boards).

Check talking to it manually, with I2C.writeTo() - check the datasheet for the I2C address to use, and see if it reacts. Some devices may take on an alternate address. Check that too - the module may be trying the other address.

Is the device known working?

Thanks. I can confirm the driver works with a generic breakout, so obviously something went wrong on the other test hardware.

So it's all sorted now?

Were you using 1v62? I'd added some code that should have given a slightly more helpful error message in the case of I2C errors :)

Yeah, it works. I tested against 1v60 and 1v62. I am still trying to clean it up and fix the 401 USB.

//Sources:
//https://github.com/technicalmachine/servo-pca9685
//https://github.com/adafruit/Adafruit-PWM-Servo-Driver-Library
//TODO:
//Add additional modes and functions, ie.
//such as from https://github.com/arc12/PCA9685/

var C = {
	PCA9685_SUBADR1 : 0x02,
    PCA9685_SUBADR2 : 0x03,
    PCA9685_SUBADR3 : 0x04,

    MAX : 4096,
    PCA9685_MODE1 : 0x00,
    PCA9685_MODE2 : 0x01,
    PCA9685_PRESCALE : 0xFE,

    /* MODE1 bits */
    PCA9685_RESTART : 0x80, //!< Restart logic. Default disabled. Not used.
    PCA9685_EXTCLK : 0x40, //!< External clock. Default disabled. Not used.
    PCA9685_AI : 0x20, //!< Register auto-increment. Enabled by initialise()
    PCA9685_SLEEP : 0x10, //!< Sleep (osc off). Device is sleeping on POR, brought out of sleep by initialise()
    PCA9685_SUB1 : 0x08,//!< Sub-address 1 enable. Default disabled. Not used.
    PCA9685_SUB2 : 0x04, //!< Sub-address 2 enable. Default disabled. Not used.
    PCA9685_SUB3 : 0x02, //!< Sub-address 3 enable. Default disabled. Not used.
    PCA9685_ALLCALL : 0x01, //!< Respond to all-call. Default enabled. Not used.

    /* MODE2 bits. These are not actually used at present */
    PCA9685_INVRT : 0x10,
    PCA9685_OCH : 0x08,
    PCA9685_OUTDRV : 0x04,
    PCA9685_OUTNE1 : 0x02,
    PCA9685_OUTNE0 : 0x01,

    // I2C Address for "all call" (7 bit form)
    PCA9685_ALLCALLADR : 0x70, //!< 0xE0 default "all call" I2C write address (7bit => 0x70)

    LED0_ON_L : 0x06,
    LED0_ON_H : 0x07,
    LED0_OFF_L : 0x08,
    LED0_OFF_H : 0x09,

    ALLLED_ON_L : 0xFA,
    ALLLED_ON_H : 0xFB,
    ALLLED_OFF_L : 0xFC,
    ALLLED_OFF_H : 0xFD
};

exports.connect = function(_i2c,freq) {
    return new PCA9685(_i2c,freq);
};

function PCA9685(i2c, freq, address) {
  this.i2c = i2c;
  freq = typeof freq != 'undefined' ? freq : 50;
  this.setPWMFreq(freq);
  this.a = typeof address ! == 'undefined' ? address : 0x40;

  this.resetPCA9685();
}

PCA9685.prototype.resetPCA9685 = function() {
  this.i2c.writeTo(this.a, [C.PCA9685_MODE1, 0x0]);
};

PCA9685.prototype.setPWMFreq = function(freq) {
  var prescaleval = (25000000/C.MAX)/freq - 1;
  var prescale = Math.floor(prescaleval);
  
  var oldmode = this.i2c.readFrom(this.a, C.PCA9685_MODE1) | 0x10;
  var newmode = (oldmode & 0x7F) | 0x10; // sleep
  this.i2c.writeTo(this.a, [C.PCA9685_MODE1, newmode]); // go to sleep
  this.i2c.writeTo(this.a, [C.PCA9685_PRESCALE, prescale]); // set the prescaler
  this.i2c.writeTo(this.a, [C.PCA9685_MODE1, oldmode]);
  setTimeout(this.i2c.writeTo(this.a, [C.PCA9685_MODE1, oldmode | 0x80]),1);
};

PCA9685.prototype.setPWM = function(num, on, off) {

  if (num < 1 || num > 16) {
    throw "Servos are 1-indexed. Servos can be between 1-16.";
  }

  this.i2c.writeTo(this.a, [C.LED0_ON_L + (num-1)*4, on]);
  this.i2c.writeTo(this.a, [C.LED0_ON_H + (num-1)*4, on >> 8]);
  this.i2c.writeTo(this.a, [C.LED0_OFF_L + (num-1)*4, off]);
  this.i2c.writeTo(this.a, [C.LED0_OFF_H + (num-1)*4, off >> 8]);
};

// 0...180
PCA9685.prototype.moveServo = function (num, val) {
  if (num < 1 || num > 16) {
    throw "Servos are 1-indexed. Servos can be between 1-16.";
  }

  this.setPWM(num, ((val/180) * (this.high - this.low)) + this.low, Math.floor(C.MAX/100*on));
};

//I2C1.setup({scl:B8, sda:B9});
//var driver = connect(I2C1, 50);
//driver.setPWM(1,400,20);