1 files changed, 102 insertions, 0 deletions
diff --git a/sw/deps/hd44780-driver/src/bus/i2c_mcp23008.rs b/sw/deps/hd44780-driver/src/bus/i2c_mcp23008.rs
new file mode 100644
index 0000000..1ccb479
--- /dev/null
+++ b/sw/deps/hd44780-driver/src/bus/i2c_mcp23008.rs
@@ -0,0 +1,102 @@
+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 MCP23008 IC, like
+/// the one from adafruit.
+/// Connections as follows:
+///
+/// <table>
+/// <tr><th>MCP23008 pin</th><th>name</th><th>LCD pin</th></tr>
+/// <tr><td>0</td><td>N/C</td><td></td></tr>
+/// <tr><td>1</td><td>RS</td><td>4</td></tr>
+/// <tr><td>2</td><td>E</td><td>6</td></tr>
+/// <tr><td>3</td><td>DB4</td><td>11</td></tr>
+/// <tr><td>4</td><td>DB5</td><td>12</td></tr>
+/// <tr><td>5</td><td>DB6</td><td>13</td></tr>
+/// <tr><td>6</td><td>DB7</td><td>14</td></tr>
+/// <tr><td>7</td><td>Backlight</td><td></td></tr>
+/// </table>
+
+pub struct I2CMCP23008Bus<I2C: Write> {
+    i2c_bus: I2C,
+    address: u8,
+}
+
+const REG_IODIR : u8 = 0x00;
+const REG_GPIO : u8 = 0x09;
+
+impl<I2C: Write> I2CMCP23008Bus<I2C> {
+
+    /// Create a new instance of the MCP23008 I2C driver. The address of those
+    /// devices is 0b010_0xxx where x is configured by bootstrap pins.
+    pub fn new(i2c_bus: I2C, address: u8) -> Result<I2CMCP23008Bus<I2C>> {
+        let mut mcp23008 = I2CMCP23008Bus { i2c_bus, address };
+        // Set to reset values according to datasheet
+        mcp23008.write_reg(REG_IODIR, 0b1111_1111)?;
+        for reg in 0x01usize..0x0A {
+            mcp23008.write_reg(reg as u8, 0)?;
+        }
+        // Configure pins 1..=7 as outputs, see pin mapping above
+        mcp23008.write_reg(REG_IODIR, 0b0000_0001)?;
+        Ok(mcp23008)
+    }
+
+    fn write_reg(&mut self, reg: u8, value: u8) -> Result<()> {
+        let data = [reg, value];
+        self.i2c_bus.write(self.address, &data)
+            .map_err(|_| crate::error::Error)
+    }
+
+    fn set_pins(&mut self, pins: u8) -> Result<()> {
+        self.write_reg(REG_GPIO, pins)
+    }
+
+}
+
+impl<I2C: Write> DataBus for I2CMCP23008Bus<I2C> {
+    fn write<D: DelayUs<u16> + DelayMs<u8>>(
+        &mut self,
+        byte: u8,
+        data: bool,
+        delay: &mut D,
+    ) -> Result<()> {
+        let rs = if data { 0b10 } else { 0b00 };
+        let en = 0b0000_0100;
+        let backlight = 0b1000_0000; // always enable backlight
+
+        let upper_nibble = (byte & 0xF0) >> 4;
+        let lower_nibble = byte & 0x0F;
+
+        // upper nibble: [d7 d6 d5 d4]
+        // Pulse EN
+        // lower nibble: [d3 d2 d1 d0]
+        // Pulse EN
+
+        let pins = rs | backlight | (upper_nibble << 3);
+        self.set_pins(pins)?;
+
+        delay.delay_ms(1);
+
+        let pins = rs | en | backlight | (upper_nibble << 3);
+        self.set_pins(pins)?;
+
+        delay.delay_ms(1);
+
+        let pins = rs | backlight | (lower_nibble << 3);
+        self.set_pins(pins)?;
+
+        delay.delay_ms(1);
+
+        let pins = rs | en | backlight | (lower_nibble << 3);
+        self.set_pins(pins)?;
+
+        delay.delay_ms(1);
+
+        let pins = backlight | (lower_nibble << 3);
+        self.set_pins(pins)?;
+
+        Ok(())
+    }
+}