Hello,
This is in continuation of my previous question about the wrong UART speed. I got it working by starting the HF oscillator. However now the latest revision of our custon nrf52 board has external LF oscillator instead of xtal. I found a support question about enabling it:
And used that to enable the LF oscillator. However when using softdevice I can't put "3" as the source in to sd_softdevice_enable. If I do, the code to start HF will not work (sd_clock_hfclk_is_running returns false every time). If I use NRF_CLOCK_LF_SRC_Xtal, the UART baud rate is off by really lot: 115200 => 125000.
Thanks in advance, Petri L.
My "with sd" code is below:
// XXXX NOTE: Not in nrf SDK!
#define NRF_CLOCK_LF_SRC_BYPASS 3
// Low frequency clock source to be used by the SoftDevice
#define NRF_CLOCK_LFCLKSRC {.source = NRF_CLOCK_LF_SRC_BYPASS, \
.rc_ctiv = 0, \
.rc_temp_ctiv = 0, \
.xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM}
nrf_clock_lf_cfg_t clock_lf_cfg = NRF_CLOCK_LFCLKSRC;
// Initialize the SoftDevice handler module.
SOFTDEVICE_HANDLER_INIT(&clock_lf_cfg, NULL);
// Start HF clock
(void) sd_clock_hfclk_request();
uint32_t hfclk_running=0;
do
{
(void) sd_clock_hfclk_is_running(&hfclk_running);
}
while(!hfclk_running);
EDIT:
Here's the code that initializes the LF clock bypass:
void hardware_init(void)
{
// Setup board clock source, LF is given by external LF oscillator
// see: devzone.nordicsemi.com/.../
uint32_t clkSrc = NRF_CLOCK->LFCLKSRC;
app_trace_log("Before: NRF_CLOCK->LFCLKSRC: 0x%08x\r\n", clkSrc);
clkSrc |= ((1<<16) + (1<<17)); // Set BYPASS = 1, EXTERNAL = 1
app_trace_log("After: NRF_CLOCK->LFCLKSRC: 0x%08x\r\n", clkSrc);
NRF_CLOCK->LFCLKSRC = clkSrc;
}
