Add support for nrf boards that don't have an external crystal

2 files changed, 37 insertions, 7 deletions

diff --git a/ports/nrf/common-hal/bleio/Adapter.c b/ports/nrf/common-hal/bleio/Adapter.c
index 936dfcb9b..70e87cf78 100644
--- a/ports/nrf/common-hal/bleio/Adapter.c
+++ b/ports/nrf/common-hal/bleio/Adapter.c
@@ -39,17 +39,37 @@
 #include "supervisor/usb.h"
 #include "shared-bindings/bleio/Adapter.h"
 #include "shared-bindings/bleio/Address.h"
+#include "mpconfigboard.h" // for BOARD_HAS_CRYSTAL
 
 STATIC void softdevice_assert_handler(uint32_t id, uint32_t pc, uint32_t info) {
     mp_raise_msg_varg(&mp_type_AssertionError,
                       translate("Soft device assert, id: 0x%08lX, pc: 0x%08lX"), id, pc);
 }
 
+static inline bool board_has_crystal(void) {
+#ifdef BOARD_HAS_CRYSTAL
+    return BOARD_HAS_CRYSTAL == 1;
+#else
+    return false;
+#endif
+}
+
 STATIC uint32_t ble_stack_enable(void) {
-    nrf_clock_lf_cfg_t clock_config = {
-        .source = NRF_CLOCK_LF_SRC_XTAL,
-        .accuracy = NRF_CLOCK_LF_ACCURACY_20_PPM
-    };
+    nrf_clock_lf_cfg_t clock_config;
+
+    // Set low-frequency clock source to be either an external 32.768kHz crystal if one exists on the board
+    // or an internal 32.768 kHz RC oscillator otherwise
+    if (board_has_crystal()) {
+        clock_config = (nrf_clock_lf_cfg_t){
+            .source = NRF_CLOCK_LF_SRC_XTAL,
+            .accuracy = NRF_CLOCK_LF_ACCURACY_20_PPM};
+    } else {
+        clock_config = (nrf_clock_lf_cfg_t){
+            .source = NRF_CLOCK_LF_SRC_RC,
+            .rc_ctiv = 16,
+            .rc_temp_ctiv = 2,
+            .accuracy = NRF_CLOCK_LF_ACCURACY_250_PPM};
+    }
 
     uint32_t err_code = sd_softdevice_enable(&clock_config, softdevice_assert_handler);
     if (err_code != NRF_SUCCESS)
diff --git a/ports/nrf/peripherals/nrf/clocks.c b/ports/nrf/peripherals/nrf/clocks.c
index 4acb878db..de9eec6b5 100644
--- a/ports/nrf/peripherals/nrf/clocks.c
+++ b/ports/nrf/peripherals/nrf/clocks.c
@@ -26,11 +26,21 @@
  */
 
 #include "nrfx.h"
+#include "mpconfigboard.h" // for BOARD_HAS_CRYSTAL
+
+static inline bool board_has_crystal(void) {
+#ifdef BOARD_HAS_CRYSTAL
+    return BOARD_HAS_CRYSTAL == 1;
+#else
+    return false;
+#endif
+}
 
 void nrf_peripherals_clocks_init(void) {
-    // Set low-frequency clock source to be crystal. If there's a crystalless board, this will need to be
-    // generalized.
-    NRF_CLOCK->LFCLKSRC = (uint32_t)((CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos) & CLOCK_LFCLKSRC_SRC_Msk);
+    // Set low-frequency clock source to be either an external 32.768kHz crystal if one exists on the board
+    // or an internal 32.768 kHz RC oscillator otherwise
+    uint32_t clock_src = board_has_crystal() ? CLOCK_LFCLKSRC_SRC_Xtal : CLOCK_LFCLKSRC_SRC_RC;
+    NRF_CLOCK->LFCLKSRC = (uint32_t)((clock_src << CLOCK_LFCLKSRC_SRC_Pos) & CLOCK_LFCLKSRC_SRC_Msk);
     NRF_CLOCK->TASKS_LFCLKSTART = 1UL;
 
     // Wait for clocks to start.