Safety and Power Saving features of Nordic nrf52 series

[bio_student]

Hello All,

We are working on a medical device that requires BLE connectivity. We could either use the nRF52 series SOC to run the application and the BLE communications or use another MCU like the STM32 series with a BLE module. I am struggling to find any safety features like RAM parity check in the Nordic documentation. We need some inherent safety for this Class 2 medical device. STM32 series has some safety features that would suffice. So my questions are:

1.  Does the nRF52 series have safety features for error checking to ensure we can at least reset during a failure.

2. Power saving is critical and we want the CPU to operate in idle mode most of the time. How much CPU time does the BLE soft stack use or does it affect reduce the idle time significantly?

regards

Ankit

[Edvin]

Hello Ankit,

1. Unfortunately, there is no RAM parity check on the nRF Series. If there are some certain areas/variables in RAM you want to ensure isn't corrupted, you would need to implement this (writing the parity bit and checking it). There are some libraries for CRC checking, which you may be able to use instead of the parity. If you implement this, it is possible to do software resets (you may already be aware of that). For "long term" storage we have the FDS (Flash Data Storage) library, which has an included CRC check (SW), but I am not sure if this is what you are looking for.

2. The BLE stack for the nRF series is very power efficient. If you only maintain the connection (e.g. no payload), the only thing the CPU is used for is to calculate and set the channel being used in the next connection event (every connection interval). The rest is done in HW. Of course, if you transmit any actual payload data, the CPU needs to process this. But as I mentioned, the idle time is not reduced much. Most of the current being consumed comes from the radio.

Best regards,

Edvin

[bio_student]

Hello Edvin

Thank you for a prompt response. I understand your comments on power saving. Implementing a software parity check will need to be evaluated but is not preferred. We will review this information and make a decision. As of now STM option offers the safety features necessary for building a medical device.

regards

Ankit

[Edvin]

Hello Ankit,

I wish I could say that we had something similar, but that would be lying

Good luck with your review. Let me know if you have any other questions regarding the nRF52 series.

Best regards,

Edvin