https://devzone.nordicsemi.com/f/nordic-q-a/4358/nrf51822-dfuI can upgrade the firmware by MCP on air ,But there are one conditions: reset the device while holding down the Enter Bootloader Mode button or a invalid application is present in Bank 0 . because my device have not button ,so i want to updata the firmwareen-USTelligent Community 13Thu, 06 Nov 2014 17:55:29 GMThttps://devzone.nordicsemi.com/thread/15499?ContentTypeID=1Thu, 06 Nov 2014 17:55:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:47cc4124-71a3-440b-80c7-9d19c728198bJohn<p>You can use the GPREGRET register to store a flag before you reset. The bootloader can check for the flag and decide whether to enter bootloader mode or attempt to run the application. There are a couple of thread below that can provide you with the details:</p> <p><a href="https://devzone.nordicsemi.com/question/13020/start-bootloader-from-app/">DFU Thread 1</a></p> <p><a href="https://devzone.nordicsemi.com/question/2227/firmware-update-without-button-press/">DFU Thread 2</a></p><div style="clear:both;"></div>