nrf/system: add configure

embassy-nrf/Cargo.toml

@@ -31,8 +31,8 @@ embedded-hal    = { version = "0.2.4" }
 embedded-dma    = { version = "0.1.2" }
 futures     = { version = "0.3.5", default-features = false }
 
-nrf52810-pac  = { version = "0.9.0", optional = true }
-nrf52811-pac  = { version = "0.9.1", optional = true }
-nrf52832-pac  = { version = "0.9.0", optional = true }
-nrf52833-pac  = { version = "0.9.0", optional = true }
-nrf52840-pac  = { version = "0.9.0", optional = true }
+nrf52810-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
+nrf52811-pac  = { version = "0.9.1", optional = true, features = [ "rt" ]}
+nrf52832-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
+nrf52833-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
+nrf52840-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}

embassy-nrf/src/lib.rs

@@ -92,6 +92,7 @@ pub mod qspi;
 pub mod rtc;
 pub mod saadc;
 pub mod spim;
+pub mod system;
 pub mod timer;
 pub mod uarte;
 

embassy-nrf/src/system.rs

@@ -0,0 +1,76 @@
+use crate::pac;
+
+pub enum HfclkSource {
+    Internal,
+    ExternalXtal,
+}
+
+pub enum LfclkSource {
+    InternalRC,
+    Synthesized,
+    ExternalXtal,
+    ExternalLowSwing,
+    ExternalFullSwing,
+}
+
+#[non_exhaustive]
+pub struct Config {
+    pub hfclk_source: HfclkSource,
+    pub lfclk_source: LfclkSource,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            // There are hobby nrf52 boards out there without external XTALs...
+            // Default everything to internal so it Just Works. User can enable external
+            // xtals if they know they have them.
+            hfclk_source: HfclkSource::Internal,
+            lfclk_source: LfclkSource::InternalRC,
+        }
+    }
+}
+
+/// safety: must only call once.
+pub unsafe fn configure(config: Config) {
+    let r = &*pac::CLOCK::ptr();
+
+    // Start HFCLK.
+    match config.hfclk_source {
+        HfclkSource::Internal => {}
+        HfclkSource::ExternalXtal => {
+            // Datasheet says this is likely to take 0.36ms
+            r.events_hfclkstarted.write(|w| unsafe { w.bits(0) });
+            r.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
+            while r.events_hfclkstarted.read().bits() == 0 {}
+        }
+    }
+
+    // Configure LFCLK.
+    match config.lfclk_source {
+        LfclkSource::InternalRC => r.lfclksrc.write(|w| w.src().rc()),
+        LfclkSource::Synthesized => r.lfclksrc.write(|w| w.src().synth()),
+
+        LfclkSource::ExternalXtal => r.lfclksrc.write(move |w| w.src().xtal()),
+
+        LfclkSource::ExternalLowSwing => r.lfclksrc.write(move |w| {
+            w.src().xtal();
+            w.external().enabled();
+            w.bypass().disabled();
+            w
+        }),
+        LfclkSource::ExternalFullSwing => r.lfclksrc.write(move |w| {
+            w.src().xtal();
+            w.external().enabled();
+            w.bypass().enabled();
+            w
+        }),
+    }
+
+    // Start LFCLK.
+    // Datasheet says this could take 100us from synth source
+    // 600us from rc source, 0.25s from an external source.
+    r.events_lfclkstarted.write(|w| unsafe { w.bits(0) });
+    r.tasks_lfclkstart.write(|w| unsafe { w.bits(1) });
+    while r.events_lfclkstarted.read().bits() == 0 {}
+}