https://devzone.nordicsemi.com/f/nordic-q-a/3825/why-does-the-nrf51422-s210-device-reset-itself-if-i-send-more-than-9-bytes-to-the-uart-from-a-pcIf I have the PC insert 1msec byte spacing between data bytes sent to the NRF51422, it receives the message and doesn&#39;t reset. I can send messages less than 10 bytes to the NRF51422 all day long without any issues without the need of any byte spacingen-USTelligent Community 13Thu, 18 Sep 2014 02:52:57 GMThttps://devzone.nordicsemi.com/thread/13819?ContentTypeID=1Thu, 18 Sep 2014 02:52:57 GMT137ad170-7792-4731-bb38-c0d22fbe4515:14ab929a-c02e-4db2-b0a6-fa48aeef1e20michaelbester101<p>Well, it ended up being the FTDI USB to Serial Cable (3.3V version). I&#39;m not sure why, but if I reprogram the FTDI eeprom with a new descriptor and VID/PID, the 3.3V VCC power line sags whenever a serial transmission is being sent from the PC. The VCC line decays at a steady rate while TX is happing. It just happens that it takes 10 bytes sent at 115200 baudrate of time for the voltage to go below the minimum VCC operating voltage of the NRF51. When I added 1ms delay between bytes, the VCC line was able to go back to 3.3V prior to the next TX byte. I took an unaltered FTDI cable, read out the eeprom and program it&#39;s contents into my modified cables to get them back to &quot;factory state&quot;. VCC is now stiff, with no droop during TX. I need to look closer at what happened. I&#39;m curious to know what exactly caused this problem. :)</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/13818?ContentTypeID=1Wed, 17 Sep 2014 09:26:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fd4e32b0-e83f-4f64-9349-6ea58abb804dUlrich Myhre<p>Are you using any SDK modules? The default error handler in the SDK will reset the chip. If you set a breakpoint in there, you should be able to figure out what is happening by reading the UART0-&gt;EVENTS_ERROR register.</p><div style="clear:both;"></div>