Peripheral_HRS example: Only notify when connected?

[Anton Maes]

I've adapted the peripheral_hr example for my purposes and its working but one thing I see is that the example never checks if the connection is established before calling notify. 

I guess this will just fill up the buffer and shouldn't massively impact battery life but is there a simple way to check if the connection is active before calling notify? 

[Anton Maes]

Here's what I was doing before. 

setting up a timer interrupt makes sense. 

what I tried to implement in connected was actually moving the loop inside the connected callback which obviously caused problems. Setting a flag makes a lot more sense. 

void measure(int readings)
{
	static struct sensor_value weight;
	int ret;
	
	int32_t avg;

	avia_hx711_power(hx711_dev,HX711_POWER_ON);

	ret = sensor_sample_fetch(hx711_dev);
	
	if (ret != 0) {
		LOG_ERR("Cannot take measurement: %d", ret);
	} else {
		readings = 100; 
		for (int i = 0; i < readings; i++) {
			sensor_channel_get(hx711_dev, HX711_SENSOR_CHAN_WEIGHT, &weight);
			avg += weight.val1;
		}
		
		int32_t adjusted = avg/readings;
		LOG_INF("Weight: %i", adjusted);
		bt_ws_notify(adjusted);
	}

	avia_hx711_power(hx711_dev, HX711_POWER_OFF);
}


void main(void)
{
	int err;
	
	int calibration_weight = 100; // grams
	hx711_dev = DEVICE_DT_GET_ANY(avia_hx711);
	__ASSERT(hx711_dev == NULL, "Failed to get device binding");

	LOG_INF("Device is %p, name is %s", hx711_dev, hx711_dev->name);
	LOG_INF("Calculating offset...");
	//avia_hx711_tare(hx711_dev, 5);

	struct hx711_data *data = hx711_dev->data;

	data->offset = -1*(2^23);
	data->slope.val1 = 1; 
	data->slope.val2 = 0; 


	err = bt_enable(NULL);
	if (err) {
		printk("Bluetooth init failed (err %d)\n", err);
		return;
	}

	bt_ready();

	bt_conn_auth_cb_register(&auth_cb_display);

	/* Implement notification. At the moment there is no suitable way
	 * of starting delayed work so we do it here
	 */

	
	while (1) {
		k_sleep(K_SECONDS(5));

		bt_conn_foreach(connect_active,NULL);

			//LOG_INF("BT Status : %i", default_conn);
		measure(100);
			/* Battery level simulation */
		//	bas_notify();

			//log_inf("disconnected");
		


	}
}

[Karl Ylvisaker]

I am glad to read that you found the comment helpful :) 
In general it is better to move processing outside of the interrupt context, since they should be kept as short as possible.

Are you sampling at a specific interval or frequency?
If so, you might benefit from starting a timer instead, and then having that RTC / TIMER instance trigger the sampling operation when it expires.
If you are sampling at high frequencies you should also consider setting this up using PPI to connect the RTC/TIMER EVENT and the sampling TASK.
This could reduce your power consumption since the CPU does not have to wake up to trigger each sampling.

Best regards,
Karl