nrf52840: RTT shell on the custom board not working

[amiramin]

Hi,

We want to enable zephyr shell over RTT on our custom board based on nrf52840. I tried the 'shell_module' sample with prj_minimal_rtt.conf and it works fine on nrf52840 devkit with nrf5340 (version command return the zephyr version in RTT viewer ).

When I tried the same sample on our custom board, the prompt is not visible and typing command does not return the zephyr version. 

We already have another working firmware with custom dts file with ncs v2.6 with RTT logging working. The shell_module sample also does not run on our custom board (as described above)

For this specific firmware, we will later integrate the 'radio_test' application and we will not need other hardware peripherals. At beginning, we are only aiming to run the zephyr shell sample. So bare minimum board dts will be OK. 

For our custom board, we connect to it using jlink-base to a pin header and 'SWO' pin is not connected to nrf chip. Is SWO pin a must for running RTT shell ? What else can we check ?

Thanks,

Amir

[Håkon Alseth]

Hi,

 

Does your design have DCDC inductors and/or external 32 kHz xtal?

 

If any of these is not present in your design, you can try to disable them:

# Select internal RC oscillator as 32KHz clock source
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
# Disable DCDC regulator
CONFIG_BOARD_ENABLE_DCDC=n

 

Kind regards,

Håkon

[amiramin]

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC option did the trick. RTT shell is working fine both with custom board DTS and nrf52840dk DTS