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logging: backend: add KConfig option for SWO sync packets #91745

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logging: backend: add KConfig option for SWO sync packets #91745

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4 changes: 4 additions & 0 deletions doc/releases/release-notes-4.2.rst
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Expand Up @@ -190,6 +190,10 @@ New APIs and options

* :c:func:`display_clear`

* Logging

* :kconfig:option:`CONFIG_LOG_BACKEND_SWO_SYNC_PACKETS`

* Networking:

* IPv4
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9 changes: 9 additions & 0 deletions subsys/logging/backends/Kconfig.swo
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Expand Up @@ -52,6 +52,15 @@ config LOG_BACKEND_SWO_PROTOCOL_MANCHESTER

endchoice

config LOG_BACKEND_SWO_SYNC_PACKETS
bool "Synchronization packet transmission"
default y
help
Generate synchronization packets with a unique pattern in the bitstream.
If the SWO pin is used for simple UART text output on a generic terminal application,
these packets show up as special characters in regular intervals.
You can avoid that by disabling this setting.

backend = SWO
backend-str = swo
source "subsys/logging/Kconfig.template.log_format_config"
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8 changes: 6 additions & 2 deletions subsys/logging/backends/log_backend_swo.c
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Expand Up @@ -110,9 +110,13 @@ static void log_backend_swo_init(struct log_backend const *const backend)
DWT->CTRL &= (DWT_CTRL_POSTPRESET_Msk | DWT_CTRL_POSTINIT_Msk | DWT_CTRL_CYCCNTENA_Msk);
DWT->CTRL |= (DWT_CTRL_POSTPRESET_Msk | DWT_CTRL_POSTINIT_Msk);
/* Configure Formatter and Flush Control Register */
TPI->FFCR = 0x00000100;
TPI->FFCR = TPI_FFCR_TrigIn_Msk;
/* Enable ITM, set TraceBusID=1, no local timestamp generation */
ITM->TCR = 0x0001000D;
uint32_t tcr = ITM_TCR_ITMENA_Msk | ITM_TCR_DWTENA_Msk | (1 << ITM_TCR_TRACEBUSID_Pos);
#if CONFIG_LOG_BACKEND_SWO_SYNC_PACKETS
tcr |= ITM_TCR_SYNCENA_Msk;
#endif
ITM->TCR = tcr;
/* Enable stimulus port used by the logger */
ITM->TER = 1 << ITM_PORT_LOGGER;

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