I am getting -1 on the screen when I save an unint32 and read it back? I am using BLEnano

[jay]

uint32_t value = 99999;

lcd.clear(); lcd.setPosition(0,1); lcd.printf("Writing bytes 0-16\n");

i2c.start();

data[0] = 0; data[1] = 0;
data[2] = ((value >> 24) & 0xFF); i2c.write(0xA0, data, 3); wait (0.1);

data[0] = 0; data[1] = 1;
data[2] = ((value >> 16) & 0xFF); i2c.write(0xA0, data, 3); wait (0.1);

data[0] = 0; data[1] = 2;
data[2] = ((value >> 8) & 0xFF); i2c.write(0xA0, data, 3); wait (0.1);

data[0] = 0; data[1] = 3;
data[2] = (value & 0xFF); i2c.write(0xA0, data, 3); wait (0.1);

//READ //Setting read pointer to 0 value = 0; data[0] = 0; // MSB address data[1] = 0; // LSB address

i2c.write(0xA0, data, 2);

char response[4]; i2c.read(0xA0+0x01, response, 4); value = ((response[0]<<24) | (response[1]<<16) | (response[2]<<8) | response[3]);

lcd.clear(); lcd.setPosition(0,0); lcd.printf("%d", value); wait(5);

[dingari]

For the first thing, have you tried reading the response array and check what the bytes contain? I'm guessing they're all 255.

Also, this part doesn't do what the comment says:

//READ //Setting read pointer to 0 value = 0; data[0] = 0; // MSB address data[1] = 0; // LSB address

i2c.write(0xA0, data, 2);

I have no idea what device you're communicating with, but when you call i2c.write(0xA0, data, 2), your array is still data[0] = 0, data[1] = 3 and data[2] = 159 from the previous command.

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Edit 2017-04-28:

Are you sure your i2c.read() function requires you to add the read bit to the address (0xA0+1)? I don't know what I2C driver you're using, but I'd think the function would be implemented in such a manner that you'd just pass the device address (0xA0) and it automatically adds the read bit.

Try this (untested):

uint32_t value = 99999;

lcd.clear(); 
lcd.setPosition(0,1); 
lcd.printf("Writing bytes 0-16\n");

data[0] = 0; 
data[1] = 0;
data[2] = ((value >> 24) & 0xFF); 
int err_code = i2c.write(0xA0, data, 3);
wait(0.1);
if(err_code != 0) {
	lcd.clear(); 
	lcd.setPosition(0,0); 
	lcd.printf("I2C write error: %d", err_code);
	wait(5);
}

data[0] = 0; 
data[1] = 1; 
data[2] = ((value >> 16) & 0xFF); 
i2c.write(0xA0, data, 3); 
wait(0.1);

data[0] = 0; 
data[1] = 2; 
data[2] = ((value >> 8) & 0xFF); 
i2c.write(0xA0, data, 3); 
wait(0.1);

data[0] = 0; 
data[1] = 3; 
data[2] = (value & 0xFF); 
i2c.write(0xA0, data, 3); 
wait(0.1);

// Read from address 0
data[0] = 0; // MSB address 
data[1] = 0; // LSB address
i2c.write(0xA0, data, 2);

char response[4]; 
i2c.read(0xA0, response, 4);
value = (response[0]<<24) | (response[1]<<16) | (response[2]<<8) | response[3];

lcd.clear(); 
lcd.setPosition(0,0); 
lcd.printf("%d", value); 
wait(5);

And please try to refrain from multiple statements per line. It makes the code very hard to read.

[dingari]

If you get non-zero return values from the I2C functions, that means the slave isn't responding. So it's probably a configuration issue.