fix UICR check; do not use NULL for no MISO

1 files changed, 14 insertions, 4 deletions

diff --git a/ports/nrf/peripherals/nrf/nrf52840/power.c b/ports/nrf/peripherals/nrf/nrf52840/power.c
index 794872c5d..d64c536bb 100644
--- a/ports/nrf/peripherals/nrf/nrf52840/power.c
+++ b/ports/nrf/peripherals/nrf/nrf52840/power.c
@@ -25,16 +25,26 @@
  */
 
 #include "nrfx.h"
-#include "nrfx_nvmc.h"
+#include "hal/nrf_nvmc.h"
 
 void nrf_peripherals_power_init(void) {
     // Set GPIO reference voltage to 3.3V if it isn't already. REGOUT0 will get reset to 0xfffffff
     // if flash is erased, which sets the default to 1.8V
     // This matters only when "high voltage mode" is enabled, which is true on the PCA10059,
     // and might be true on other boards.
-    if (NRF_UICR->REGOUT0 == 0xffffffff) {
-        nrfx_nvmc_word_write((uint32_t) &NRF_UICR->REGOUT0, UICR_REGOUT0_VOUT_3V3 << UICR_REGOUT0_VOUT_Pos);
-        // Must reset to make enable change.
+    if (NRF_UICR->REGOUT0 == 0xffffffff && NRF_POWER->MAINREGSTATUS & 1) {
+        // Expand what nrf_nvmc_word_write() did.
+        // It's missing from nrfx V2.0.0, and nrfx_nvmc_word_write() does bounds
+        // checking which prevents writes to UICR.
+        // Reported: https://devzone.nordicsemi.com/f/nordic-q-a/57243/nrfx_nvmc-h-api-cannot-write-to-uicr
+        NRF_NVMC->CONFIG = NRF_NVMC_MODE_WRITE;
+        while (!(NRF_NVMC->READY & NVMC_READY_READY_Msk)) {}
+        NRF_UICR->REGOUT0 = UICR_REGOUT0_VOUT_3V3 << UICR_REGOUT0_VOUT_Pos;
+        __DMB();
+        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
+        NRF_NVMC->CONFIG = NRF_NVMC_MODE_READONLY;
+
+        // Must reset to enable change.
         NVIC_SystemReset();
     }
 }