Rewrite MAX5719 Driver into a separated file

src/laser_diode/max5719.rs

@@ -0,0 +1,53 @@
+use crate::device::sys_timer::sleep;
+use fugit::MegahertzU32;
+use stm32f4xx_hal::{
+    hal::{blocking::spi::Transfer, digital::v2::OutputPin},
+    spi,
+};
+
+pub const SPI_MODE: spi::Mode = spi::Mode {
+    polarity: spi::Polarity::IdleLow,
+    phase: spi::Phase::CaptureOnFirstTransition,
+};
+pub const SPI_CLOCK_MHZ: MegahertzU32 = MegahertzU32::from_raw(30);
+
+pub const MAX_VALUE: u32 = 0xFFFFF;
+
+pub struct Dac<SPI: Transfer<u8>, S1: OutputPin, S2:OutputPin> {
+    spi: SPI,
+    cs_n: S1,
+    load_n: S2,
+}
+
+impl<SPI: Transfer<u8>, S1: OutputPin, S2: OutputPin> Dac<SPI, S1, S2> {
+    pub fn new(spi: SPI, mut cs_n: S1, mut load_n: S2) -> Self {
+        let _ = cs_n.set_high();
+        let _ = load_n.set_high();
+
+        Dac { spi, cs_n, load_n}
+    }
+
+    fn write(&mut self, buf: &mut [u8]) -> Result<(), SPI::Error> {
+        let _ = self.cs_n.set_low();
+        self.spi.transfer(buf)?;
+        let _ = self.cs_n.set_high();
+        sleep(1);
+        // must be high for >= 20 ns
+        let _ = self.load_n.set_low();
+        // must be low for >= 20 ns
+        sleep(1);
+        let _ = self.load_n.set_high();
+        Ok(())
+    }
+
+    pub fn set(&mut self, value: u32) -> Result<u32, SPI::Error> {
+        let value = value.min(MAX_VALUE) << 4;
+        let mut buf = [
+            ((value >> 16) & 0xFF) as u8,
+            ((value >> 8) & 0xFF) as u8,
+            ((value >> 0) & 0xFF) as u8,
+        ];
+        self.write(&mut buf)?;
+        Ok(value)
+    }
+}

src/laser_diode/mod.rs

@@ -1 +1,2 @@
-pub mod current_sources;
+pub mod current_sources;
+pub mod max5719;