nRF52832 Some periferals disabled when using BLE

[Claudio Ferraro]

I was reading a review of this product from a 3th party and they was claiming that a disadvantage about using this chip is that "Some peripherals and resources are not available, or are limited, when BLE is enabled". Anyway they wasn't specifying which peripherals. May somebody tell me exactly about which peripherals they're referring ? Regards

[Ole Bauck]

Hi,

Since our chip is a System On Chip with only one core, there will be limitation, but this is the case with all chips in this category.

He may be talking about the restricted or blocked hardware peripherals listed here.

Restricted peripherals are accessed through the SoftDevice API. This is to ensure that the SoftDevice runs as it is supposed to. Trying to access the restricted peripherals directly (not through the API) may lead to hardfault or unstable operation.

Blocked peripherals cannot normally be accessed by the application. These are peripherals that is required for Bluetooth connection as for example RADIO, TIMER0 and RTC0. You can however access these peripherals if you use the timeslot API. You will need this if you want to use the RADIO for other protocols than Bluetooth Low Energy. You can also use this if you have timing critical tasks you need to perform that involves the CPU (more on that later). For the timers there are multiple other timer peripherals you can use (TIMER1:4 or RTC1:2).

The CPU will be blocked for some time to do SoftDevice tasks. The highest interrupt priority levels is restricted to the SoftDevice. The SoftDevice will run most of the tasks at a priority level in between the ones available for the application, see here. This means that the SoftDevice, if enabled, may at any time interrupt the application and this should be in the developers mind. The time the SoftDevice blocks the application is often not long and is documented in the SoftDevice Specification here.

As Endnode says, DMA is nice to let peripherals run in parallel with the SoftDevice. The nRF52 has DMA on most of the hardware peripherals used for communication with other devices (like SPI, TWI, UART etc).

Hope this answered your question.

Ole