https://devzone.nordicsemi.com/f/nordic-q-a/6044/why-doesn-t-the-twi-transmit-an-addressUsing the nRF51422 with the TWI hardware version. Just playing around to verify signals with the following code which just configures the TWI1 and then repeats continuously with a master transmit of one data byte=0x57. I get a 7 clock transitions onen-USTelligent Community 13Tue, 17 Mar 2015 19:16:13 GMThttps://devzone.nordicsemi.com/thread/21133?ContentTypeID=1Tue, 17 Mar 2015 19:16:13 GMT137ad170-7792-4731-bb38-c0d22fbe4515:61571fe7-1832-4227-9cf0-e33ce6ded42aStian R&#248;ed Hafskjold<p>You should set <code>NRF_TWI1-&gt;ENABLE = 5</code> not 1, to enable the twi.</p> <p>Now you code will output the address. Remember to shift the address one bit right, since the last bit is for ACK/NACK (and is automatically shifted left in the TWI HW):</p> <pre><code>NRF_TWI1-&gt;ADDRESS=(0x78 &gt;&gt; 1); </code></pre> <p>Also, if you do not have a slave that ACK the address, it will only transmit the address and stop, so you will not see the data byte.</p><div style="clear:both;"></div>