nrf5340: add internal capacitor config

1 files changed, 155 insertions, 1 deletions

diff --git a/embassy-nrf/src/lib.rs b/embassy-nrf/src/lib.rs
index 23888b390..f2cf0d77e 100644
--- a/embassy-nrf/src/lib.rs
+++ b/embassy-nrf/src/lib.rs
@@ -360,6 +360,133 @@ pub mod config {
         pub regmain: bool,
     }
 
+    /// Settings for the internal capacitors.
+    #[cfg(feature = "nrf5340-app-s")]
+    pub struct InternalCapacitors {
+        /// Config for the internal capacitors on pins XC1 and XC2.
+        pub hfxo: Option<HfxoCapacitance>,
+        /// Config for the internal capacitors between pins XL1 and XL2.
+        pub lfxo: Option<LfxoCapacitance>,
+    }
+
+    /// Internal capacitance value for the HFXO.
+    #[cfg(feature = "nrf5340-app-s")]
+    #[derive(Copy, Clone)]
+    pub enum HfxoCapacitance {
+        /// 7.0 pF
+        _7_0pF,
+        /// 7.5 pF
+        _7_5pF,
+        /// 8.0 pF
+        _8_0pF,
+        /// 8.5 pF
+        _8_5pF,
+        /// 9.0 pF
+        _9_0pF,
+        /// 9.5 pF
+        _9_5pF,
+        /// 10.0 pF
+        _10_0pF,
+        /// 10.5 pF
+        _10_5pF,
+        /// 11.0 pF
+        _11_0pF,
+        /// 11.5 pF
+        _11_5pF,
+        /// 12.0 pF
+        _12_0pF,
+        /// 12.5 pF
+        _12_5pF,
+        /// 13.0 pF
+        _13_0pF,
+        /// 13.5 pF
+        _13_5pF,
+        /// 14.0 pF
+        _14_0pF,
+        /// 14.5 pF
+        _14_5pF,
+        /// 15.0 pF
+        _15_0pF,
+        /// 15.5 pF
+        _15_5pF,
+        /// 16.0 pF
+        _16_0pF,
+        /// 16.5 pF
+        _16_5pF,
+        /// 17.0 pF
+        _17_0pF,
+        /// 17.5 pF
+        _17_5pF,
+        /// 18.0 pF
+        _18_0pF,
+        /// 18.5 pF
+        _18_5pF,
+        /// 19.0 pF
+        _19_0pF,
+        /// 19.5 pF
+        _19_5pF,
+        /// 20.0 pF
+        _20_0pF,
+    }
+
+    #[cfg(feature = "nrf5340-app-s")]
+    impl HfxoCapacitance {
+        /// The capacitance value times two.
+        pub(crate) const fn value2(self) -> i32 {
+            match self {
+                HfxoCapacitance::_7_0pF => 14,
+                HfxoCapacitance::_7_5pF => 15,
+                HfxoCapacitance::_8_0pF => 16,
+                HfxoCapacitance::_8_5pF => 17,
+                HfxoCapacitance::_9_0pF => 18,
+                HfxoCapacitance::_9_5pF => 19,
+                HfxoCapacitance::_10_0pF => 20,
+                HfxoCapacitance::_10_5pF => 21,
+                HfxoCapacitance::_11_0pF => 22,
+                HfxoCapacitance::_11_5pF => 23,
+                HfxoCapacitance::_12_0pF => 24,
+                HfxoCapacitance::_12_5pF => 25,
+                HfxoCapacitance::_13_0pF => 26,
+                HfxoCapacitance::_13_5pF => 27,
+                HfxoCapacitance::_14_0pF => 28,
+                HfxoCapacitance::_14_5pF => 29,
+                HfxoCapacitance::_15_0pF => 30,
+                HfxoCapacitance::_15_5pF => 31,
+                HfxoCapacitance::_16_0pF => 32,
+                HfxoCapacitance::_16_5pF => 33,
+                HfxoCapacitance::_17_0pF => 34,
+                HfxoCapacitance::_17_5pF => 35,
+                HfxoCapacitance::_18_0pF => 36,
+                HfxoCapacitance::_18_5pF => 37,
+                HfxoCapacitance::_19_0pF => 38,
+                HfxoCapacitance::_19_5pF => 39,
+                HfxoCapacitance::_20_0pF => 40,
+            }
+        }
+    }
+
+    /// Internal capacitance value for the LFXO.
+    #[cfg(feature = "nrf5340-app-s")]
+    pub enum LfxoCapacitance {
+        /// 6 pF
+        _6pF = 1,
+        /// 7 pF
+        _7pF = 2,
+        /// 9 pF
+        _9pF = 3,
+    }
+
+    #[cfg(feature = "nrf5340-app-s")]
+    impl From<LfxoCapacitance> for super::pac::oscillators::vals::Intcap {
+        fn from(t: LfxoCapacitance) -> Self {
+            match t {
+                LfxoCapacitance::_6pF => Self::C6PF,
+                LfxoCapacitance::_7pF => Self::C7PF,
+                LfxoCapacitance::_9pF => Self::C9PF,
+            }
+        }
+    }
+
     /// Configuration for peripherals. Default configuration should work on any nRF chip.
     #[non_exhaustive]
     pub struct Config {
@@ -367,6 +494,10 @@ pub mod config {
         pub hfclk_source: HfclkSource,
         /// Low frequency clock source.
         pub lfclk_source: LfclkSource,
+        #[cfg(feature = "nrf5340-app-s")]
+        /// Internal capacitor configuration, for use with the `ExternalXtal` clock source. See
+        /// nrf5340-PS §4.12.
+        pub internal_capacitors: InternalCapacitors,
         #[cfg(not(any(feature = "_nrf5340-net", feature = "_nrf54l")))]
         /// DCDC configuration.
         pub dcdc: DcdcConfig,
@@ -388,6 +519,8 @@ pub mod config {
                 // xtals if they know they have them.
                 hfclk_source: HfclkSource::Internal,
                 lfclk_source: LfclkSource::InternalRC,
+                #[cfg(feature = "nrf5340-app-s")]
+                internal_capacitors: InternalCapacitors { hfxo: None, lfxo: None },
                 #[cfg(not(any(feature = "_nrf5340", feature = "_nrf91", feature = "_nrf54l")))]
                 dcdc: DcdcConfig {
                     #[cfg(feature = "nrf52840")]
@@ -687,6 +820,27 @@ pub fn init(config: config::Config) -> Peripherals {
         cortex_m::peripheral::SCB::sys_reset();
     }
 
+    // Configure internal capacitors
+    #[cfg(feature = "nrf5340-app-s")]
+    {
+        if let Some(cap) = config.internal_capacitors.hfxo {
+            let mut slope = pac::FICR.xosc32mtrim().read().slope() as i32;
+            let offset = pac::FICR.xosc32mtrim().read().offset() as i32;
+            // slope is a signed 5-bit integer
+            if slope >= 16 {
+                slope -= 32;
+            }
+            let capvalue = (((slope + 56) * (cap.value2() - 14)) + ((offset - 8) << 4) + 32) >> 6;
+            pac::OSCILLATORS.xosc32mcaps().write(|w| {
+                w.set_capvalue(capvalue as u8);
+                w.set_enable(true);
+            });
+        }
+        if let Some(cap) = config.internal_capacitors.lfxo {
+            pac::OSCILLATORS.xosc32ki().intcap().write(|w| w.set_intcap(cap.into()));
+        }
+    }
+
     let r = pac::CLOCK;
 
     // Start HFCLK.
@@ -753,7 +907,7 @@ pub fn init(config: config::Config) -> Peripherals {
             config::LfclkSource::ExternalLowSwing => lfxo = true,
             #[cfg(not(feature = "lfxo-pins-as-gpio"))]
             config::LfclkSource::ExternalFullSwing => {
-                #[cfg(all(feature = "_nrf5340-app"))]
+                #[cfg(feature = "_nrf5340-app")]
                 pac::OSCILLATORS.xosc32ki().bypass().write(|w| w.set_bypass(true));
                 lfxo = true;
             }