initial commit, working 48k version for tortilla hardware

src/hw.rs

@@ -0,0 +1,56 @@
+pub(crate) struct PllConstants {
+    pub m: u16,   // 1-65535
+    pub n: u8,    // 1-255
+    pub p: u8,    // 1-31
+    pub selp: u8, // 5 bits
+    pub seli: u8, // 6 bits
+}
+
+impl PllConstants {
+    pub(crate) const fn new(n: u8, m: u16, p: u8) -> Self {
+        assert!(n != 0, "1 <= N <= 255");
+        assert!(m != 0, "1 <= M <= 65535");
+        assert!(p != 0 && p <= 31, "1 <= P <= 31");
+
+        // Following ripped from lpc55-hal and made const
+        // UM 4.6.6.3.2
+        let selp = {
+            let v = (m >> 2) + 1;
+            if v < 31 { v } else { 31 }
+        } as u8;
+
+        let seli = {
+            let v = match m {
+                m if m >= 8000 => 1,
+                m if m >= 122 => 8000 / m,
+                _ => 2 * (m >> 2) + 3,
+            };
+
+            if v < 63 { v } else { 63 }
+        } as u8;
+        // let seli = min(2*(m >> 2) + 3, 63);
+        Self {
+            n,
+            m,
+            p,
+            selp,
+            seli,
+        }
+    }
+}
+impl defmt::Format for PllConstants {
+    fn format(&self, fmt: defmt::Formatter) {
+        let factor = f32::from(self.m) / (f32::from(self.n) * 2.0 * f32::from(self.p));
+
+        defmt::write!(
+            fmt,
+            "m: {} n: {} p: {} selp: {} seli: {} fout: fin * {}",
+            self.m,
+            self.n,
+            self.p,
+            self.selp,
+            self.seli,
+            factor
+        );
+    }
+}