nrf51822 Chip wont restart after battery is below the operating voltage and get recharged(buttonless design)

[harry4951]

Hi,

We have a nrf51822 based custom board with no button, we use accelerometer tap detection to wake up the system. Currently there is no software protection for the battery voltage, which means the battery will drain until it is below the operating voltage. But the whole system wont restart even if the battery is fully charged again afterwards. I have to disconnect the battery and reconnect it to the board then the system will work again. 

I duplicate the issue with an external power supply and it has the same issue: Tune the voltage to the operating voltage(3.3V), connect it to the board(Now start to do advertising, LED blinking), then slowly reduce the voltage to around 2.7V until there is no advertising no blinking, after that increase the voltage to 3.3V again and now the board wont work. Only after I disconnect and reconnect the power will the board back to life again.

Is there any software setting to deal with this issue without the need to disconnect and reconnect the power? also the design is buttonless which means there is no button to press reset.

Thanks

CJ

[ketiljo]

There's no reason for the nRF51 to stop working at 2.7 V. I think maybe the regulator is playing with you here. Try to bypass the regulator and see if the error is still present.

[harry4951]

Hi, this post is different from the question I posted in the private channel. This is the design with non-rechargeable battery.

The issue was found out from the rechargeable solution but since I dont have the hardware at hand. I had to use the previous design, which I had hardware sample at hand. But in the end this non-rechargeable solution has the same issue. I used power supply to connect with BAT P1 P2, lower the voltage and increase back to the normal voltage, the system wont restart unless I disconnect the cable and reconnect.

[ketiljo]

Try connect a 1M resistor between SWDIO and ground. The reset function of the SWDIO pin will be upset when the voltage drops. 

[harry4951]

Problem solved, thank you!