From d6019ded26bf8b5dd3a9ad7a0ae0231868c8fc13 Mon Sep 17 00:00:00 2001
From: geeksville <kevinh@geeksville.com>
Date: Thu, 4 Jun 2020 16:45:31 -0700
Subject: [PATCH 1/2] Place data from .uicrREGOUT0 into UICR.REGOUT0 flash
 word.

Used to set VCC voltage upon power-up.
---
 linker/nrf52840.ld | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/linker/nrf52840.ld b/linker/nrf52840.ld
index fcfa425e..bc1adc12 100644
--- a/linker/nrf52840.ld
+++ b/linker/nrf52840.ld
@@ -41,6 +41,9 @@ MEMORY
   
   /** Location in UICR where mbr params page address is stored. */
   UICR_MBR_PARAM_PAGE(r) : ORIGIN = 0x10001018, LENGTH = 0x04
+
+  /** Location in UICR of REGOUT0 (used to set voltage levels for VCC at boot) */
+  UICR_REGOUT0(r) : ORIGIN = 0x10001304, LENGTH = 0x04
 }
 
 SECTIONS
@@ -81,6 +84,12 @@ SECTIONS
     KEEP(*(.uicrMbrParamsPageAddress))
   } > UICR_MBR_PARAM_PAGE
 
+  /* Write REGOUT0 in UICR. */
+  .uicrREGOUT0 :
+  {
+    KEEP(*(.uicrREGOUT0))
+  } > UICR_REGOUT0
+
   .dbl_reset(NOLOAD) :
   {
 

From 9478eb7ed3eebe0cd41a3a137e9673e376ca8a23 Mon Sep 17 00:00:00 2001
From: geeksville <kevinh@geeksville.com>
Date: Tue, 16 Jun 2020 09:29:46 -0700
Subject: [PATCH 2/2] address comments from review (warn users, also support
 833)

---
 linker/nrf52833.ld | 16 ++++++++++++++++
 linker/nrf52840.ld |  9 ++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/linker/nrf52833.ld b/linker/nrf52833.ld
index 46a23dca..4cac961e 100644
--- a/linker/nrf52833.ld
+++ b/linker/nrf52833.ld
@@ -39,6 +39,16 @@ MEMORY
     
   /** Location in UICR where mbr params page address is stored. */
   UICR_MBR_PARAM_PAGE(r) : ORIGIN = 0x10001018, LENGTH = 0x04
+
+  /** Location in UICR of REGOUT0 (used to set voltage levels for VCC at boot)
+   *
+   * IMPORTANT NOTE: This controls the voltage provided on the VCC output of the CPU. Changing this value from the default
+   * can physically damage parts on your board.  If using a SWD debugger you should consider connecting the Vref input
+   * for that debugger to the VCC rail. Think carefully before using this feature.
+   * Example usage:
+   * __attribute__ ((section(".uicrREGOUT0"))) volatile uint32_t m_uicr_regout0 = 0xfffffff4;
+   */
+  UICR_REGOUT0(r) : ORIGIN = 0x10001304, LENGTH = 0x04
 }
 
 SECTIONS
@@ -74,6 +84,12 @@ SECTIONS
     KEEP(*(.uicrMbrParamsPageAddress))
   } > UICR_MBR_PARAM_PAGE
 
+  /* Write REGOUT0 in UICR. */
+  .uicrREGOUT0 :
+  {
+    KEEP(*(.uicrREGOUT0))
+  } > UICR_REGOUT0
+
   .dbl_reset(NOLOAD) :
   {
 
diff --git a/linker/nrf52840.ld b/linker/nrf52840.ld
index bc1adc12..dfd11e2d 100644
--- a/linker/nrf52840.ld
+++ b/linker/nrf52840.ld
@@ -42,7 +42,14 @@ MEMORY
   /** Location in UICR where mbr params page address is stored. */
   UICR_MBR_PARAM_PAGE(r) : ORIGIN = 0x10001018, LENGTH = 0x04
 
-  /** Location in UICR of REGOUT0 (used to set voltage levels for VCC at boot) */
+  /** Location in UICR of REGOUT0 (used to set voltage levels for VCC at boot)
+   *
+   * IMPORTANT NOTE: This controls the voltage provided on the VCC output of the CPU. Changing this value from the default
+   * can physically damage parts on your board.  If using a SWD debugger you should consider connecting the Vref input
+   * for that debugger to the VCC rail. Think carefully before using this feature.
+   * Example usage:
+   * __attribute__ ((section(".uicrREGOUT0"))) volatile uint32_t m_uicr_regout0 = 0xfffffff4;
+   */
   UICR_REGOUT0(r) : ORIGIN = 0x10001304, LENGTH = 0x04
 }