No printk on custom nRF9160, but ok on nRF9160DK

[okwestern]

I have a problem with printk/LOG in one program (samples/sensor/bmi160). All my programs, except this one, gives me serial output from both logging (LOG_INF etc) and printf/printk. The program in question gives me printk and LOG_xxx to my nRF9160DK board, but only LOG_xxx to my custom nRF9160 board. Very annoying. What parameter suppresses printk on one board but not the other, and is also program specific (since printk works with the custom board for all my other programs). I've compared application specific files (e.g. prj.conf) across working programs and the questionable program without luck.

Here is the prj.conf:

CONFIG_GPIO=y
CONFIG_GPIO_NRFX=y
CONFIG_STDOUT_CONSOLE=y
CONFIG_SERIAL=y
CONFIG_SENSOR=y

# SPI
CONFIG_SPI=y
CONFIG_SPI_NRFX=y
CONFIG_SPI_2=y
CONFIG_SPI_NRFX=y
CONFIG_MAIN_STACK_SIZE=4096
CONFIG_SPI_NRFX_RAM_BUFFER_SIZE=256
CONFIG_I2C=n

CONFIG_UART_INTERRUPT_DRIVEN=y

CONFIG_BMI160=y
CONFIG_BMI160_TRIGGER_OWN_THREAD=y
CONFIG_BMI160_TRIGGER=y

#Debug Specific
CONFIG_DEBUG=n
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=4
CONFIG_LOG_MAX_LEVEL=4
CONFIG_LOG_BACKEND_UART=y

I also tried to add this to the bmi160 driver Kconfig:

config PRINTK
    bool "Send printk() to console"
    default y
    help
      This option directs printk() debugging output to the supported
      console device, rather than suppressing the generation
      of printk() output entirely. Output is sent immediately, without
      any mutual exclusion or buffering.

[okwestern]

When I disabled config_sensor=y, it would print.

I found that the bmi160 driver would hang, and since the drivers are initiated at boot, it never reached main() where the printk happens. All good now, except the provided bmi160 driver doesn't work. But that's another ticket.