How to perform reset on nRF51822 chip?

[Andrew]

We have made a custom board using nRF51822 connected to a MPU6050 accelerometer running on a battery.

Currently, we have issues performing reset on the chip. We have to reload the firmware to reset it. Is there a way to reset the device through unplugging the board from the battery then plugging it back on?

[Vidar Berg]

Do you mean that your application doesn't start if you do a power-cycle, but only when you perform re-flash? Both methods should result in a reset of the chip.

[Andrew]

Yes. Vidar Berg. That is exactly what happens. I would like to know how the nRF51822 chip resets. I may be able to know the problem if I had a better idea on the nRF51822 reset process.

[Vidar Berg]

It sounds strange. Is it possible that the board was still powered via the debug connection when you tried power-cycling the board? Also, do you see the same behavior with the SDK examples on your board?

[Andrew]

Hi Vidar. Actually this is a strange issue. I currently use a nRF51822 evaluation board with a MPU6050 module. My firmware uses the MPU6050's zero-G interrupt to detect falls. After flashing the board, everything works fine. Then after removing the power and connecting it back on, the fall detection doesn't work. It is only through re-flashing the board or pressing the reset button will the firmware works properly again.

Is it possible doing a power cycling doesn't completely reset the chip?

For our production boards, we might not have space for a button. So we have to do power on then off to do the resetting.

[Nicolas Tzovanis]

I'm having a similar issue using a MPU-6050. I initialize the IMU (set acceleration range, gyroscope range, etc) at startup, but I check that it wasn't initialized before using a global variable. The variable is initialized in 0 and after initializing the MPU is set to 1. When I power cycle the nRF (disconnect and reconnect the battery), the value of the variable is not set back to 1, thus not initializing the MPU. If I reset the nRF using Jlink, the variable is correctly set to 1 after reseting.