Setting XL1 & XL2 as GPIO does not work.

[Cecylia]

Hi there,

We are not using external Crystal for this design and thinking of reusing XL1 & XL2 (Pin 0 and Pin 1) for SPI (MISO & MOSI).  But I found that I can't set properly set these pins as GPIO output.

Something as simple as:

nrf_gpio_cfg_output(0);
nrf_gpio_pin_set(0);

will not bring the line up (I checked with a scope).  Are there additional steps needed to make these pins GPIO? Or, it's not possible to use them as regular GPIO?


Thanks,
Cecylia

[Stian Røed Hafskjold]

Hi, yes you have to make sure that LFCLKSRC is set to 0. If you haven't set this register in your project it defaults to 0 already.

Are you using custom HW or the PCA10056 DK? If you are using the DK pin 0 and 1 are routed to the crystal and you need to cut SB1/2 and solder SB3/4 in order to route the pins out to the GPIO header. Please check out the schematics or this list.

[Cecylia]

I'm using custom HW.  I did not explicitly set the source ---or so I thought--- but the sdk_config.h that I copied over apparently set it to XTAL.  So when I called 'nrf_drv_clock_init()' then it sets it to XTAL instead of RC.


When I change this CLOCK_CONFIG_LF_SRC  to 0 then I can use XL0 and XL1.  Yay!  Thanks!

// <o> CLOCK_CONFIG_LF_SRC - LF Clock Source

// <0=> RC
// <1=> XTAL
// <2=> Synth

#ifndef CLOCK_CONFIG_LF_SRC
#define CLOCK_CONFIG_LF_SRC 1
#endif