README.rst
1.. _nrf53_sync_rtc_sample:
2
3Synchronized RTC
4################
5
6Overview
7********
8
9Sample is showing how RTC clocks used for system clock on application and network
10core are synchronized. The result of synchronization is an offset value on network
11core which can be applied to the system tick for logging timestamping.
12
13Sample is using IPM driver and IPC HAL to produce events which occur at same time on
14both cores. Application core periodically reads current system tick and stores it in
15the shared memory and triggers IPC task which results in the interrupt on the network
16core. In the context of the IPC interrupt handler, network core is logging timestamp
17from shared memory and local system tick updated by the offset. User can observe
18that before synchronization procedure is completed, timestamps differ significantly
19and once procedure is completed timestamps are synchronized. Network core timestamp
20may be slightly behind (usually 1 tick) due to latency introduced by the
21interrupt handling.
22
23For simplicity and low latency sample is not using more sophisticated IPM protocols.
24
25Building the application for nrf5340dk_nrf5340_cpuapp
26*****************************************************
27
28.. zephyr-app-commands::
29 :zephyr-app: samples/boards/nrf/nrf53_sync_rtc
30 :board: nrf5340dk_nrf5340_cpuapp
31 :goals: flash "flash --hex-file build/sync_rtc_net-prefix/src/sync_rtc_net-build/zephyr/zephyr.hex"
32
33Open a serial terminals (for example Minicom or PuTTY) and connect the board with the
34following settings:
35
36- Speed: 115200
37- Data: 8 bits
38- Parity: None
39- Stop bits: 1
40
41When you reset the development kit, the following messages (one for master and one for remote) will appear on the corresponding serial ports:
42
43.. code-block:: console
44
45 *** Booting Zephyr OS build v2.7.0-rc1-89-ge755863d66c9 ***
46 [00:00:00.306,915] <inf> main: IPC send at 10056 ticks
47 [00:00:00.356,903] <inf> main: IPC send at 11695 ticks
48 [00:00:00.406,921] <inf> main: IPC send at 13334 ticks
49 [00:00:00.456,939] <inf> main: IPC send at 14973 ticks
50 [00:00:00.506,958] <inf> main: IPC send at 16612 ticks
51 [00:00:00.556,976] <inf> main: IPC send at 18251 ticks
52 [00:00:00.606,994] <inf> main: IPC send at 19890 ticks
53 [00:00:00.657,012] <inf> main: IPC send at 21529 ticks
54 [00:00:00.707,031] <inf> main: IPC send at 23168 ticks
55 [00:00:00.757,049] <inf> main: IPC send at 24807 ticks
56
57
58.. code-block:: console
59
60 *** Booting Zephyr OS build v2.7.0-rc1-89-ge755863d66c9 ***
61 [00:00:00.054,534] <inf> main: Local timestamp: 1787, application core timestamp: 10056
62 [00:00:00.104,553] <inf> main: Local timestamp: 3426, application core timestamp: 11695
63 [00:00:00.154,571] <inf> main: Local timestamp: 5065, application core timestamp: 13334
64 [00:00:00.204,589] <inf> main: Local timestamp: 6704, application core timestamp: 14973
65 [00:00:00.254,608] <inf> main: Local timestamp: 8343, application core timestamp: 16612
66 [00:00:00.514,892] <inf> sync_rtc: Updated timestamp to synchronized RTC by 8270 ticks (252380us)
67 [00:00:00.557,006] <inf> main: Local timestamp: 18252, application core timestamp: 18251
68 [00:00:00.607,025] <inf> main: Local timestamp: 19891, application core timestamp: 19890
69 [00:00:00.657,043] <inf> main: Local timestamp: 21530, application core timestamp: 21529
70 [00:00:00.707,061] <inf> main: Local timestamp: 23169, application core timestamp: 23168
71 [00:00:00.757,080] <inf> main: Local timestamp: 24807, application core timestamp: 24807
72
73Observe that initially logging timestamps for the corresponding events on both cores
74do not match. Same with local and remote timestamps reported on network core. After
75RTC synchronization is completed they start to match.
76
