Trying to use dev kit without nRFGo Starter kit

[John Vourvoulakis]

Hi,

I am trying to use the PCA10004 board in a custom application without the use of starter kit. When I burn the nRF51822 chip with my custom program, in my custom hardware everything is working properly. But when I disconnect the segger programmer (that is purchased with nordic's dev kit) the application is not running. When I have the PCA10004 connected to the nRFGo Starter kit then my application is working properly even if I disconnect the segger programmer. The only way I found that PCA10004 can work properly in my custom hardware even if I have the segger programmer disconnected is to solder a pull up resistor to the pin SWDIO (the resistor R1 in the PCA10004 schematic files). This pull up resistor is not necessary when the board is connected to the Starter kit. I cannot find what more has starter kit against my custom hardware. It is not a major issue since I have a working application but obviously there is something that I am missing here. Does anyone know what is it? Thank you in advance.

Best Regards, John

[Stefan Birnir Sverrisson]

Hi John

On the first hardware revision of nRF51 (XLR1), a pulldown resistor was needed on the SWDCLK pin. On the second revision (XLR2) the resistor is not needed as it is present internally on the nRF51. However, a few customers have applied also an external pulldown resistor to make the pulldown stronger. These few customers were experiencing some signal noise on their PCB, causing a spike on the SWDCLK line and putting the nRF51 therefore into debug mode. We have tested 470ohm external resistor on the SWDCLK pin and that has proven to be good for most programmers/debuggers, they can still drive the SWDCLK line. So having the internal ~12k resistor and the 12k external resistor in paralell is quite ok, although in most cases it would not be necessary to add an external resistor.