Device freezes when jumping between main and Bluetooth write thread

RE: Device freezes when jumping between main and Bluetooth write thread

jksu — Tue, 14 Feb 2023 19:56:46 GMT

Hello Kenneth! Thanks for the quick reply, I've done as you advised and fixed the blocking behavior within that thread. I also discovered that I had areas in my main() that were blocking as well, which I corrected with the else sleep solution you recommended.

Once I corrected those, the issue went away! Thanks for figuring it out!

RE: Device freezes when jumping between main and Bluetooth write thread

Kenneth — Tue, 14 Feb 2023 10:01:48 GMT

Looking at the following you shared this thread is blocking if the if() statement is not true, so I added an else:

/* Function for writing messages from peripheral to central (mobile device, or other) */
void ble_write_thread(void)
{
	/* Don't go any further until BLE is initialized */
	k_sem_take(&ble_init_ok, K_FOREVER);

	//int i = 0;
	for (;;)
	{
		if ((current_conn != 0) && (databuf != 0))
		{
			bt_nus_send(NULL, databuf, 10);
			printk("\nMessage Sent!");
			k_msleep(100); //this is where the thread priority is passed back to main()
			printk("Returned to ble_write_thread\n");
		}
		else
		{
		    k_msleep(100); //nothing to do
		}
	}
}

Likely there are better ways to do this, but at least it avoid it to be blocking.

RE: Device freezes when jumping between main and Bluetooth write thread

jksu — Mon, 13 Feb 2023 21:27:46 GMT

Just an updated comment to include additional observed behavior

This error seems to have a higher chance to occur if I let the code run idly through main for a few minutes without sending a message.

So if I a) tile device to send a message, b) return to main thread, c) wait for 5-10 minutes, d) tilt device to send a message, this has a very high chance to get stuck before returning to main

Edit: I managed to replicate the issue while in Debug mode, and when the code got stuck, I clicked Pause, and ended up in cpu_idle.S, line 105, cpsie i

	/*
	 * Wait for all memory transactions to complete before entering low
	 * power state.
	 */
	dsb

	/* Enter low power state */
	wfi

	/*
	 * Clear PRIMASK and flush instruction buffer to immediately service
	 * the wake-up interrupt.
	 */
	cpsie	i
	isb

	bx	lr