Baseband and Kernel Functions

To maximize the Bluetooth Low Energy connection stability, the stack must be provided sufficient processing time. We recommended that you:

Set the stack interrupts to the highest priority to prevent preemp.tion or ISR processing delays.
Minimize the continuous time when interrupts are disabled
Have the application call BLE_Kernel_Process() at least once per Bluetooth connection interval.

In the current sample code, all Bluetooth and non-Bluetooth interrupt priorities are set to 0 (highest priority). In future SDK updates, the priority of non-Bluetooth interrupts will be lowered. We recommend that customers make this change to their own code to lower the priority of all non-Bluetooth interrupts to maximize the Bluetooth Low Energy connection stability.

Use of the event kernel and baseband are primarily supported by the functions described in the "Event Kernel Support Functions" table. These functions initialize and execute these components, while supporting transitions between different power modes. Function prototypes for these functions are included through ble.h, and these prototypes are defined in ble/rwip.h.

Table: Event Kernel Support Functions
Function	Description
BLE_Initialize	Initialize the event kernel and Bluetooth baseband for use within an application.
BLE_Baseband_Sleep	Place the Bluetooth baseband to sleep if the current Bluetooth Low Energy stack and the event kernel state indicate it is safe.
BLE_Kernel_Process	Execute any pending events that have been scheduled with the event kernel.
BLE_Baseband_Is_Awake	Check if the Bluetooth baseband is awake.

BLE_Initialize

Prototype:

void BLE_Initialize(uint8_t * param_ptr)

Parameters:

Table: BLE_Initialize Parameters
Type	Parameters	Description
uint8_t *	param_ptr	Reserved for future use (input/output parameter)

Return:

None

Description:

Initializes the Bluetooth Low Energy stack and the event kernel for use within an application.

Example

/* Initialize the kernel and Bluetooth stack */

uint8_t param;

BLE_Initialize(&param);

BLE_Baseband_Sleep

Prototype:

uint8_t BLE_Baseband_Sleep(struct ble_sleep_api_param_tag *param_ptr)

Parameters:

Table: BLE_Baseband_Sleep Parameters
Type	Parameters	Description
struct ble_sleep_api_param_tag *	param_ptr	param_ptr.app_sleep_request = Application sleep request; set to 1 if the Bluetooth baseband is intended to go to sleep when possible, 0 if the system is meant to stay awake param_ptr.max_sleep_duration = Requested maximum sleep duration in multiples of 312.5 μs (if set to zero, no maximum sleep duration is used) param_ptr.min_sleep_duration = Requested minimum sleep duration in μs param_ptr.calculated_sleep_duration = Return value, in low power baseband clock cycles, providing the calculated time written to the BB_DEEPSLWKUP register

NOTE: Minimum sleep duration that BLE_BASEBAND_SLEEP() sets is the maximum value of min_sleep_duration and the BB_ENBPRESET_TWOSC bit field from the BB_ENBPRESET register.

Return:

Allowed sleep state.

RWIP_DEEP_SLEEP if the baseband controller has been put to sleep, the baseband timer is set, and the core can switch to Sleep Mode (after saving the baseband and RF registers) or Standby Mode.
RWIP_CPU_SLEEP if the core can be put to sleep, but the system is not meant to enter Sleep Mode or Standby Mode.
RWIP_ACTIVE otherwise.

Description:

A user application needs to call this function when sending the Bluetooth Low Energy stack into Sleep Mode. This function checks whether it is the right time for the event kernel and Bluetooth Low Energy stack to go to sleep or not. If the return value is RWIP_DEEP_SLEEP, the BB controller is already in sleep and the BB timer has been started with the desired sleep duration.

Example:

/* Attempt to place the device to sleep */

struct ble_sleep_api_param_tag param;

param.app_sleep_request = 1;

param.max_sleep_duration = MAX_SLEEP_DURATION;

param.min_sleep_duration = MIN_SLEEP_DURATION;

switch(BLE_Baseband_Sleep(&param))

{

case RWIP_DEEP_SLEEP:

{

/* Save the baseband and RF registers, then go to sleep */

BB_Sleep(POWER_MODE);

break;

}

case RWIP_CPU_SLEEP:

{

/* Wait for interrupt */

__WFI();

break;

}

case RWIP_ACTIVE:

default:

{

}

BLE_Kernel_Process

Prototype:

void BLE_Kernel_Process(void)

Parameters:

None

Return:

None

Description:

Execute any pending events that have been scheduled with the event kernel.

Example:

/* Main application loop:

* - Run the kernel scheduler

* - Refresh the watchdog and wait for an interrupt before continuing */

while (1)

{

BLE_Kernel_Process();

/* Refresh the watchdog timer */

SYS_WATCHDOG_REFRESH();

/* Wait for an event before executing the scheduler again */

__WFI();

}

BLE_Baseband_Is_Awake

Prototype:

bool BLE_Baseband_Is_Awake(void)

Parameters:

None

Return:

True if the Bluetooth baseband is awake, false otherwise.

Description:

Check if the Bluetooth baseband is awake.

Example:

/* Check if the Bluetooth baseband is still awake */

if (BLE_Baseband_Is_Awake())

{

BLE_Baseband_Sleep(&param);

}