nRF9160 HFINT accuracy problem.

RE: nRF9160 HFINT accuracy problem.

Håkon Alseth — Fri, 30 Oct 2020 11:51:20 GMT

[quote user="bbslhb"]So can I use HFXO as crystal source for nRF9160 "LTE_BLE_GATEWAY" 1M baud rate?[/quote]

Yes, you can use that as a HFCLK source. By default you use the HFINT, but by issuing TASKS_HFCLKSTART, you start up the HFXO.

[quote user="bbslhb"]Or HFXO can only be used by modem?[/quote]

It can be used by the application as well. Just start it using NRF_CLOCK->TASKS_HFCLKSTART and wait for it to start up (approx. 1 ms)

You can check the HFCLKSTAT register to see which is running.

Kind regards,

Håkon

RE: nRF9160 HFINT accuracy problem.

bbslhb — Fri, 30 Oct 2020 09:03:10 GMT

“There's an HFXO in the nRF9160 SIP, which is used by the modem for the radio communication etc.”

So can I use HFXO as crystal source for nRF9160 "LTE_BLE_GATEWAY" 1M baud rate?

Or HFXO can only be used by modem?

NRF_CLOCK->TASKS_HFCLKSTART=1 only use HFCLK but not defined HFINT or HFXO.

Both HFINT and HFXO can be the source of HFCLK.

RE: nRF9160 HFINT accuracy problem.

Håkon Alseth — Fri, 30 Oct 2020 08:38:11 GMT

Hi,

There's an HFXO in the nRF9160 SIP, which is used by the modem for the radio communication etc.

If you want to start the HFCLK, the simplest form is NRF_CLOCK->TASKS_HFCLKSTART=1;, then wait and clear the EVENTS_HFCLKSTARTED event.

To use the clock subsys, you can do it similar to this: https://github.com/nrfconnect/sdk-nrf/blob/master/samples/bluetooth/direct_test_mode/src/dtm.c#L462-L479

static int clock_init(void)
{
	int err;
	const struct device *clock;

	clock = device_get_binding("CLOCK");
	if (!clock) {
		printk("Unable to find clock device binding\n");
		return -ENODEV;
	}

	err = clock_control_on(clock, CLOCK_CONTROL_NRF_SUBSYS_HF);
	if (err) {
		printk("Unable to turn on the clock: %d", err);
	}

	return err;
}

[quote user=""] So will the HFINT accuracy cause problem if I run lte_ble_gateway on nRF9160 and hci_uart on nRF52840 in nRF9160DK platform because the default HCI baud rate is 1M?[/quote]

It can, especially for larger transmission (due to drift), as the max. tolerance is given to 5%: https://infocenter.nordicsemi.com/topic/ps_nrf9160/pmu_oscillators.html?cp=2_0_0_4_0_3_3#unique_847745536

Kind regards,

Håkon

RE: nRF9160 HFINT accuracy problem.

bbslhb — Fri, 30 Oct 2020 08:13:35 GMT

Or is there a way to use HFXO in nRF9160 to generate accurate 1M baud rate to run LTE_BLE_GATEWAY sample code?

The hardware platform is nRF9160DK and HCI_UART is run on nRF52840 of nRF9160DK.