Restricted Memory Range + BLE concerns

RE: Restricted Memory Range + BLE concerns

Vidar Berg — Tue, 10 Oct 2023 06:48:05 GMT

sd_softdevice_enable() activates the Softdevice, which involves starting the LF clock. However, this has no direct relationship with the RTOS.

We are not creating a separate Freertos task for advertising_start(), but it is being called by the Softdevice task when it starts here:

[quote user="morpho"]Is the only reason to use nrf_sdh_freertos_init with advertising_start to prevent it from running before the scheduler starts? Why is advertising_start related to the scheduler in any way though?[/quote]

Connectable advertising should not be started before the Softdevice task is running, since the Softdevice task is required for retrieving connection and other Softdevice events.

[quote user="morpho"]I have a scheduler in my main application and that only runs after the BLE is initialized which involves setting up the advertisement so I don't know if there really is a need to set up a task for advertising_start in particular; we can just set up the LF clock and call it a day no?[/quote]

Calling advertising_start() will make the device start advertising immediately.

RE: Restricted Memory Range + BLE concerns

morpho — Mon, 09 Oct 2023 18:48:48 GMT

Setting optimization to 0 did it! That was a whacky experience.

[quote userid="4240" url="~/f/nordic-q-a/104368/restricted-memory-range-ble-concerns/449117"]The low-frequency (LF) clock is the 32 kHz clock used by the RTOS scheduler and the SoftDevice to keep track of time. The clock is started by sd_softdevice_enable() in nrf_sdh_enable_request().[/quote]

I see, so in short, it 1) enables the LF clock 2) creates a task for advertising_start

Is the only reason to use nrf_sdh_freertos_init with advertising_start to prevent it from running before the scheduler starts? Why is advertising_start related to the scheduler in any way though?

I have a scheduler in my main application and that only runs after the BLE is initialized which involves setting up the advertisement so I don't know if there really is a need to set up a task for advertising_start in particular; we can just set up the LF clock and call it a day no?

RE: Restricted Memory Range + BLE concerns

Vidar Berg — Fri, 06 Oct 2023 05:56:13 GMT

Hi,

Which compiler optimization level are you using when debugging the application? From your video, it appears the debugger might be displaying the r0 value, but it's hard to confirm without the project in front of me.

Optimization should be disabled here when debugging:

[quote user="morpho"]Sorry, what's LF clock? it's not enabled by nrf_sdh_freertos_init() I reckon? What function enables it?[/quote]

The low-frequency (LF) clock is the 32 kHz clock used by the RTOS scheduler and the SoftDevice to keep track of time. The clock is started by sd_softdevice_enable() in nrf_sdh_enable_request().

RE: Restricted Memory Range + BLE concerns

morpho — Wed, 04 Oct 2023 15:31:21 GMT

2. How is a function parameter pointing to an area outside an application region? How's it possible? Does it mean the memory is fully consumed?
I already have the Restricted Memory Access enabled

3. Sorry, what's LF clock? it's not enabled by nrf_sdh_freertos_init() I reckon? What function enables it?

Related to the first point: in the same function GetMessage, do you see why would val contain nothing and value gets set to 0 after the strcmp? Pls refer to the video

devzone.nordicsemi.com/.../cast_5F00_strange_5F00_behavior.mov

DataUnit is an alias for uint8_t

Weirdly, it happens with char* but I need char* to use strcmp

void UARTApp::UARTCallback(Fifo<DataUnit> fifoRx)        // within UART ISR
{
     char* ptr2 = reinterpret_cast<char*>(parsedInput); // Restricted Range
     unsigned char* ptr1 = reinterpret_cast<unsigned char*>(parsedInput); // OK
     uint8_t* ptr = reinterpret_cast< uint8_t*>(parsedInput); // OK
     
     // ...
 }

RE: Restricted Memory Range + BLE concerns

Vidar Berg — Wed, 04 Oct 2023 09:24:01 GMT

Hi,

1. Calling nrf_sdh_freertos_init() with advertising_start() ensures the advertiser is not started before the scheduler is running. The connection event will not be processed if the connection is established before the scheduler is started.

2. Restricted memory range indicates that the pointer is pointing to an area outside of the application region. You can set the setting shown below to 'No' to find out what the address is.

3. The Softdevice is responsible for starting the LF clock and the scheduler will not run without it.