Using RTT with internal Clock

[Niclas Heitz]

Hello,

I am currently experiencing some problems, when i try using RTT output and the internal clock.

When using an external crystal, everything is working.

The following two code snippets are the configurations i use respectively.

#define NRF_CLOCK_LFCLKSRC_RC   {.source        = NRF_CLOCK_LF_SRC_RC,            \
                                 .rc_ctiv       = 16,                                \
                                 .rc_temp_ctiv  = 2,                                \
                                 .xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_500_PPM}

#define NRF_CLOCK_LFCLKSRC      {.source        = NRF_CLOCK_LF_SRC_XTAL,            \
                                 .rc_ctiv       = 0,                                \
                                 .rc_temp_ctiv  = 0,                                \
                                 .xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM}

I couldn't find any record specifying requirements for the clock to use RTT.

Any help would be appreciated.

Best regards,

Niclas

[bjorn-spockeli]

Hi Niclas, 

which SDK version are you using? Are you using a nRF52 DK or a custom nRF52823 board when you're seeing this issue?

Best regards

Bjørn 

[Niclas Heitz]

Hi Bjørn,

I am using SDK12.2.0.

I tested it on our custom board and also with the nRF52 DK  PCA10040 V1.1.0.

The results were identical.

Thanks,

Niclas

[bjorn-spockeli]

From a previous question I see that you're migrating from SDK 12.2.0 to SDK v14.0.0. 

I did a quick test in SDK v14.0.0 by modifying the ble_app_hrs example to use the internal RC and not the LFXO and enabling RTT logging I am seeing RTT output in Segger RTT Viewer. 

Best regards

Bjørn 

[bjorn-spockeli]

I also see the RTT log output in RTT Viewer if I do the same in the ble_app_hrs example in  SDK v12.2.0. SO in other words this should work fine. Are you able to reproduce it with a SDK example? I assume that you're seeing this issue with a custom application. 

[Niclas Heitz]

I tried modifying the ble_app_hrs example myself, but i don't see any RTT output.

I only replaced the NRF_CLOCK_LFCLKSRC with the NRF_CLOCK_LFCLKSRC_RC i posted above.

Is there something else i need to change?

I also tried the ble_app_hrs_pca10040_s132.hex for reference, but there was no RTT ouput either.

Is RTT not enabled in the precompiled hex?