continue CAN

va416xx-hal/src/can/mod.rs

@@ -1,6 +1,6 @@
-use arbitrary_int::{u2, u3, u4, u7};
+use arbitrary_int::{u2, u3, u4, u7, Number};
 
-use crate::{clock::Clocks, enable_peripheral_clock, PeripheralSelect};
+use crate::{clock::Clocks, enable_peripheral_clock, time::Hertz, PeripheralSelect};
 
 pub mod regs;
 
@@ -38,16 +38,62 @@ pub struct ClockConfig {
     sjw: u2,
 }
 
+#[derive(Debug, thiserror::Error)]
+#[error("sjw must be less than or equal to the smaller tseg value")]
+pub struct InvalidSjwError(u2);
+
+/// Sample point between 0 and 1.0 for the given time segments.
+pub const fn sample_point(tseg1: u4, tseg2: u3) -> f32 {
+    let tseg1_val = tseg1.value() as f32;
+    (tseg1_val + 1.0) / (1.0 + tseg1_val + tseg2.value() as f32)
+}
+
+#[derive(Debug, thiserror::Error)]
+#[error("invalid sample point {sample_point} for tseg1 {tseg1} and tseg2 {tseg2}.")]
+pub struct InvalidSamplePointError {
+    tseg1: u4,
+    tseg2: u3,
+    /// Sample point, should be larger than 0.5 (50 %) but was not.
+    sample_point: f32,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum ClockConfigError {
+    #[error("invalid sjw: {0}")]
+    InvalidSjw(#[from] InvalidSjwError),
+    #[error("invalid sample point: {0}")]
+    InvalidSamplePoint(#[from] InvalidSamplePointError),
+}
+
 impl ClockConfig {
     /// New clock configuration from the raw configuration values.
-    pub fn new(prescaler: u7, tseg1: u4, tseg2: u3, sjw: u2) -> Self {
-        Self {
+    ///
+    /// The synchronization jump width MUST be smaller than the smaller of the time segment
+    /// configuration values. The sample point must also be larger than 50 %.
+    pub fn new(prescaler: u7, tseg1: u4, tseg2: u3, sjw: u2) -> Result<Self, ClockConfigError> {
+        let smaller_tseg = core::cmp::min(tseg1.value(), tseg2.value());
+        if sjw.value() > smaller_tseg {
+            return Err(InvalidSjwError(sjw).into());
+        }
+        let sample_point = sample_point(tseg1, tseg2);
+        if sample_point < 0.5 {
+            return Err(InvalidSamplePointError {
+                tseg1,
+                tseg2,
+                sample_point,
+            }.into());
+        }
+        Ok(Self {
             prescaler,
             tseg1,
             tseg2,
             sjw,
-        }
+        })
     }
+
+    pub fn from_bitrate(clocks: &Clocks, bitrate: Hertz, prescaler: u7, tseg1: u4, tseg2: u3, sjw: u2) {}
+
+    pub fn from_sample_point(clocks: &Clocks, bitrate: Hertz, sample_point: f32) {}
 }
 
 impl Can {