https://devzone.nordicsemi.com/f/nordic-q-a/38446/nrf51822-resets-on-weird-situationsI was developing an green house system for plants which was based on nRF51822 SoC. The system was fully completed and working fine except one problem which was reset of nRF51822. I could not figure out what was causing this reset problem. Followingen-USTelligent Community 13Fri, 14 Sep 2018 13:32:09 GMThttps://devzone.nordicsemi.com/thread/148839?ContentTypeID=1Fri, 14 Sep 2018 13:32:09 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6925be9d-9f07-413b-8915-e04d64a33b9crun_ar<p>Can you measure vdd using a scope or power analyzer to check that it is stable when you enable uart? If it&#39;s not stable, what is the ripple?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/148826?ContentTypeID=1Fri, 14 Sep 2018 12:32:35 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c7b9569d-0852-48ff-a480-3f971658f0bcJamal<p>No, it does not only cause if communication is on going. It happens if UART is initialized.<br />One more thing which i noticed is from my other design was the following:</p> <p>I left two pads for UART RX and TX on the PCB. The UART peripheral was enabled. So whenever those pads come in contact with ground (earth or my work table) or my hand or finger while touching the board. nRF51 Resets.</p> <p>I have no idea what exactly happens if I enable UART.</p> <p>And in the same board if UART is disabled, I touch everywhere on the PCB, even on the TX and RX pads but nothing goes wrong.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/148809?ContentTypeID=1Fri, 14 Sep 2018 12:05:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:11cba693-49b2-42c0-914e-801c5dc5396arun_ar<p>Agree. Most likely there is to much ripple on the provided vdd voltage, so the chip is reset.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/148480?ContentTypeID=1Wed, 12 Sep 2018 16:48:37 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4f78d332-6a20-44ec-b016-97ac9169e38cAndre<p>A power on reset is also generated on a brown-out, as the quote from the nordic site says. So this could still be a brown-out. A poorly designed power supply could be sensitive to minor changes on the input power caused by plugging in plug in a socket.&nbsp;</p> <p>Does just initialising the UART trigger the issue, or does it only trigger when there is actual communication?&nbsp;</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/148376?ContentTypeID=1Wed, 12 Sep 2018 10:49:16 GMT137ad170-7792-4731-bb38-c0d22fbe4515:52c045c1-a09e-4536-9b34-b43a65e808daJamal<p>Hi,</p> <p>I checked the reset reason register also. It says the power on reset is generated!</p> <p>It not about the unstable input voltage i guess. Because it never happened when UART is not enabled.</p> <p>If enabled, the system works fine in normal conditions. Lets say i connect something like my laptop charger in any power socket in the room. The nRF51 resets. There is no direct connection between the nRF51 and other appliances except that the power supply(which is powering nRF51 system) is connected in the same place where we switch appliances.</p> <p>If we do not use the UART at all. This problem do not appear.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/148348?ContentTypeID=1Wed, 12 Sep 2018 08:34:10 GMT137ad170-7792-4731-bb38-c0d22fbe4515:df124166-2352-4966-8a5b-423da5e2665eAndre<p>Can you read the NRF_POWER-&gt;RESETREAS register to determine the reset reason.</p> <p style="padding-left:30px;"><span>If none of the reset sources are flagged, this indicates that the chip was reset from the on-chip reset generator, which will indicate a power-on-reset or a brownout reset.</span></p> <p>If the reason is a brown out, I suggest adding some capacitors between VCC and GND.&nbsp;</p><div style="clear:both;"></div>