| .. _nrf-clock-skew-sample: |
| |
| nRF5x Clock Skew Demo |
| ##################### |
| |
| Overview |
| ******** |
| |
| This sample uses the API for correlating time sources to measure the |
| skew between HFCLK (used for the CPU) and LFCLK (used for system time). |
| It also shows how to use this skew to correct durations measured in the |
| LFCLK domain to durations in the HFCLK domain. |
| |
| The ``CONFIG_APP_ENABLE_HFXO`` Kconfig option can be select to configure |
| the high frequency clock to use a crystal oscillator rather than the |
| default RC oscillator. (Capabilities like Bluetooth that require an |
| accurate high-frequency clock generally enable this source |
| automatically.) The relative error is significantly lower when HFXO is |
| enabled. |
| |
| Requirements |
| ************ |
| |
| This application uses any nRF51 DK or nRF52 DK board for the demo. |
| |
| Building, Flashing and Running |
| ****************************** |
| |
| .. zephyr-app-commands:: |
| :zephyr-app: samples/boards/nrf/clock_skew |
| :board: nrf52dk_nrf52840 |
| :goals: build flash |
| :compact: |
| |
| Running: |
| |
| |
| Sample Output |
| ============= |
| |
| .. code-block:: console |
| |
| *** Booting Zephyr OS build v2.5.0-rc3-94-g06a4b650467b *** |
| Power-up clocks: LFCLK[ON]: Running LFXO ; HFCLK[OFF]: Running HFINT |
| Start TIMER_0: 0 |
| Timer-running clocks: LFCLK[ON]: Running LFXO ; HFCLK[OFF]: Running HFINT |
| Checking TIMER_0 at 16000000 Hz against ticks at 32768 Hz |
| Timer wraps every 268 s |
| |
| Ty Latest Base Span Err |
| HF 00:00:00.015666 |
| LF 00:00:00.404937 |
| Started sync: 0 |
| |
| Ty Latest Base Span Err |
| HF 00:00:09.978436 00:00:00.015666 00:00:09.962769 |
| LF 00:00:10.414520 00:00:00.404937 00:00:10.009582 00:00:00.046813 |
| RHF 00:00:09.978435 -00:00:00.000000 |
| Skew 0.995323 ; err 4676818 ppb |
| |
| Ty Latest Base Span Err |
| HF 00:00:19.959136 00:00:00.015666 00:00:19.943469 |
| LF 00:00:20.441589 00:00:00.404937 00:00:20.036651 00:00:00.093182 |
| RHF 00:00:19.959117 -00:00:00.000018 |
| Skew 0.995349 ; err 4650592 ppb |
| |
| Ty Latest Base Span Err |
| HF 00:00:29.937181 00:00:00.015666 00:00:29.921514 |
| LF 00:00:30.468627 00:00:00.404937 00:00:30.063690 00:00:00.142176 |
| RHF 00:00:29.937175 -00:00:00.000005 |
| Skew 0.995271 ; err 4729151 ppb |
| |
| Ty Latest Base Span Err |
| HF 00:00:39.917347 00:00:00.015666 00:00:39.901680 |
| LF 00:00:40.495666 00:00:00.404937 00:00:40.090728 00:00:00.189048 |
| RHF 00:00:39.917339 -00:00:00.000008 |
| Skew 0.995284 ; err 4715502 ppb |
| |
| Ty Latest Base Span Err |
| HF 00:00:49.899493 00:00:00.015666 00:00:49.883826 |
| LF 00:00:50.522674 00:00:00.404937 00:00:50.117736 00:00:00.233910 |
| RHF 00:00:49.899486 -00:00:00.000007 |
| Skew 0.995333 ; err 4667222 ppb |
| |
| Ty Latest Base Span Err |
| HF 00:00:59.878166 00:00:00.015666 00:00:59.862499 |
| LF 00:01:00.549713 00:00:00.404937 00:01:00.144775 00:00:00.282276 |
| RHF 00:00:59.878154 -00:00:00.000011 |
| Skew 0.995307 ; err 4693269 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 00:02:59.654855 00:00:00.015666 00:02:59.639188 |
| LF 00:03:00.873901 00:00:00.404937 00:03:00.468963 00:00:00.829775 |
| RHF 00:02:59.654857 00:00:00.000001 |
| Skew 0.995402 ; err 4597902 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 00:04:59.410593 00:00:00.015666 00:04:59.394926 |
| LF 00:05:01.198181 00:00:00.404937 00:05:00.793243 00:00:01.398317 |
| RHF 00:04:59.410594 00:00:00.000001 |
| Skew 0.995351 ; err 4648745 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 00:09:58.829511 00:00:00.015666 00:09:58.813845 |
| LF 00:10:02.008911 00:00:00.404937 00:10:01.603973 00:00:02.790128 |
| RHF 00:09:58.829509 -00:00:00.000002 |
| Skew 0.995362 ; err 4637837 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 00:29:56.607589 00:00:00.015666 00:29:56.591923 |
| LF 00:30:05.250732 00:00:00.404937 00:30:04.845794 00:00:08.253871 |
| RHF 00:29:56.607585 -00:00:00.000004 |
| Skew 0.995427 ; err 4573166 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 00:59:43.781443 00:00:00.015666 00:59:43.765776 |
| LF 01:00:00.085113 00:00:00.404937 00:59:59.680175 00:00:15.914399 |
| RHF 00:59:43.781535 00:00:00.000092 |
| Skew 0.995579 ; err 4421055 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 01:59:37.666395 00:00:00.015666 01:59:37.650728 |
| LF 02:00:09.810913 00:00:00.404937 02:00:09.405975 00:00:31.755247 |
| RHF 01:59:37.666057 -00:00:00.000338 |
| Skew 0.995595 ; err 4404723 ppb |
| ... |
| Ty Latest Base Span Err |
| HF 05:58:33.905236 00:00:00.015666 05:58:33.889570 |
| LF 06:00:08.604980 00:00:00.404937 06:00:08.200042 00:01:34.310472 |
| RHF 05:58:33.904338 -00:00:00.000898 |
| .. |
| Skew 0.995635 ; err 4364550 ppb |
| Ty Latest Base Span Err |
| HF 11:56:59.503922 00:00:00.015666 11:56:59.488255 |
| LF 12:00:06.793182 00:00:00.404937 12:00:06.388244 00:03:06.899989 |
| RHF 11:56:59.503948 00:00:00.000025 |
| Skew 0.995674 ; err 4325747 ppb |
