I2C on DUE - only address is output on serial, no data!

Hardware Arduino Due
#1

Hi Guys,
after hours of struggling, i decided to ask the community...
my goal is very simple: i want to use the I2C (pin 20 & 21) on my DUE to output 8 bits.

I uploaded the SerialWrite sketch and i connected my DSO Nano scope to the SDA and SCL.
What i can see (sorry, the NanoDSO cant take snapshots....:stuck_out_tongue: ) is that the Due is sending out only the address part of my digital pattern.
i put 3 lines of code here:

Wire.beginTransmission(4); // transmit to device #4
Wire.write(0xF); // THIS LINE SEEMS USELESS BUT IT'S WHAT I NEED WORKING
Wire.endTransmission(); // stop transmitting

I'd expect to see a sequence of "ones" (0XF = 1111) after the address but the only thing that change the waveform is when i change the address, nO matter what value i put into the Wire.write.
The clock is set at 400KHz (i need the fastest).
Does anybody have any hint?
Thank you in advance!
A.

#2

It requires the slave device to ACK (acknowledge) or it won't send the data.

#3

Thank you Morgan! So simple!
pity I can't simulate the transmission with the Due and the scope and I need the whole system...
I hoped to be able to program all in the comfort of the office but i'll have to go to the lab... :grinning:

#4