How to configure multiple notifications per connection event

[eyalasko]

Hi, 

I'm trying to improve throughput by increasing the notification buffer number to 6. (SD132, V 5.0.0, SDK14.2)

I tried to follow the sequence charts as well as use sd_ble_cfg_set() in ble_stack_init() but it does not seem to work.

	ble_cfg_t ble_cfg;
	ble_cfg.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = 6;	
	APP_ERROR_CHECK(sd_ble_cfg_set(APP_BLE_CONN_CFG_TAG, &ble_cfg, ram_start));

What is the correct way to do it?

Thanks

[eyalasko]

Hi Andy, 

Thanks for your prompt response. 

Unfortunately I think that the default queue depth is 1 which severely limits the throughput... 

[Andy]

Mm it seems you're right. However, if you queue a new notification as soon as you get the tx complete event, you shouldn't have any issues.

In any case what you're doing is alright, but you need to change APP_BLE_CONN_CFG_TAG to BLE_CONN_CFG_GATTS.

[eyalasko]

Thanks.

I've changed to BLE_CONN_CFG_GATTS as you advised and increased APP_RAM_START (+0x100 bytes)

Strangely, nrf_sdh_ble_enable() returns NRF_ERROR_NO_MEM, even if I explicitly set hvn_tx_queue_size= 1...

	ble_cfg_t ble_cfg;
	ble_cfg.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = 1;	// Tried 6
	err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_cfg, ram_start); 
	APP_ERROR_CHECK(err_code);	

    // Enable BLE stack.
    err_code = nrf_sdh_ble_enable(&ram_start);  // this call returns NRF_ERROR_NO_MEM
    APP_ERROR_CHECK(err_code);

[Andy]

You need to adjust your memory regions in the linker file. 

[eyalasko]

I've changed memory settings in the project properties page (Keil IDE)

Nevertheless, I expect  that setting hvn_tx_queue_size=1 which is the default value should not change the softdevice's memory footprint

[Andy]

Well the notifications need to be queued somewhere. If you increase the queue size, naturally the memory footprint will increase as well.