1 files changed, 71 insertions, 0 deletions
diff --git a/sw/deps/hd44780-driver/src/bus/i2c.rs b/sw/deps/hd44780-driver/src/bus/i2c.rs
new file mode 100644
index 0000000..160e205
--- /dev/null
+++ b/sw/deps/hd44780-driver/src/bus/i2c.rs
@@ -0,0 +1,71 @@
+use embedded_hal::blocking::delay::{DelayMs, DelayUs};
+use embedded_hal::blocking::i2c::Write;
+
+use crate::{bus::DataBus, error::Result};
+
+/// This module supports I2C backpacks with a PCF8574 IC.
+/// Connections as follows:
+///
+/// <table>
+/// <tr><th>PCF8574 pin</th><th>name</th><th>LCD pin</th></tr>
+/// <tr><td>P0</td><td>RS</td><td>4</td></tr>
+/// <tr><td>P1</td><td>RW</td><td>5</td></tr>
+/// <tr><td>P2</td><td>E</td><td>6</td></tr>
+/// <tr><td>P3</td><td>Backlight</td><td></td></tr>
+/// <tr><td>P4</td><td>DB4</td><td>11</td></tr>
+/// <tr><td>P5</td><td>DB5</td><td>12</td></tr>
+/// <tr><td>P6</td><td>DB6</td><td>13</td></tr>
+/// <tr><td>P7</td><td>DB7</td><td>14</td></tr>
+/// </table>
+
+pub struct I2CBus<I2C: Write> {
+    i2c_bus: I2C,
+    address: u8,
+}
+
+const BACKLIGHT: u8 = 0b0000_1000;
+const ENABLE: u8 = 0b0000_0100;
+// const READ_WRITE: u8 = 0b0000_0010; // Not used as no reading of the `HD44780` is done
+const REGISTER_SELECT: u8 = 0b0000_0001;
+
+impl<I2C: Write> I2CBus<I2C> {
+    pub fn new(i2c_bus: I2C, address: u8) -> I2CBus<I2C> {
+        I2CBus { i2c_bus, address }
+    }
+
+    /// Write a nibble to the lcd
+    /// The nibble should be in the upper part of the byte
+    fn write_nibble<D: DelayUs<u16> + DelayMs<u8>>(
+        &mut self,
+        nibble: u8,
+        data: bool,
+        delay: &mut D,
+    ) {
+        let rs = match data {
+            false => 0u8,
+            true => REGISTER_SELECT,
+        };
+        let byte = nibble | rs | BACKLIGHT;
+
+        let _ = self.i2c_bus.write(self.address, &[byte, byte | ENABLE]);
+        delay.delay_ms(2u8);
+        let _ = self.i2c_bus.write(self.address, &[byte]);
+    }
+}
+
+impl<I2C: Write> DataBus for I2CBus<I2C> {
+    fn write<D: DelayUs<u16> + DelayMs<u8>>(
+        &mut self,
+        byte: u8,
+        data: bool,
+        delay: &mut D,
+    ) -> Result<()> {
+        let upper_nibble = byte & 0xF0;
+        self.write_nibble(upper_nibble, data, delay);
+
+        let lower_nibble = (byte & 0x0F) << 4;
+        self.write_nibble(lower_nibble, data, delay);
+
+        Ok(())
+    }
+}