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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(())
}
}
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