nRF52840 Custom board wont start under Zephyr

[Jeff Seaman]

I am working with the nRF52840 under Zephyr to develop some wireless sensors.  The issue I am having I build a test module using the nrf/samples/light.  This running on the development board worked great for the purpose of testing some functions on the main unit.  I wanted to run two of these boards, I have a custom board with LED_1 on the same pins as the Development kit.  I program the custom board it runs fine through the debugger.  I disconnect the debugger and the board will not start from a power up. 

I also tested using the zephyr/samples/hello_world example as it is much simpler.  I added the LED so there was no back biasing powering the board from the USB/serial adapter.

I have also tried using a custom board definition for the Adafruit nRF52840 Sensor board that runs as expected.

1) power up the board no LEDs

2) pull the reset pin low and bring high no response

If I plug in the Jlink and Connect LED comes on2451.hello_world.zip

I have attached the schematic and project fileReceiver board Rev D.pdf

[Jeff Seaman]

From the Raytac MBT50Q data sheet pg 38

32MHz crystal and RF (VDD) DC/DC inductor (Reg1) are already inside the module.

From Nordic 

• Case ID: 251512   nRF52840 REG0 & REG1

• There is a surprising amount of passives under the RF can of the module - including above capacitor(s).

I think that is answering the Question.

The needed parts are on the Raytac module but not on my board so I have to use the LDO regulator by  setting BOARD_ENABLE_DCDC to disabled.

This can be done in the Configure nRF Connect SDK Project tool

or by changing the setting in the board Kconfig file when creating a custom board

config BOARD_ENABLE_DCDC
           bool "Enable DCDC mode"
           select SOC_DCDC_NRF52X
           default y
           depends on BOARD_NRF52840DK_NRF52840

Thank you for setting me on the correct path I did not look into the module for the differences in the two boards just the Adafruit schematic