add lcd-writer

.gitignore

@@ -0,0 +1,2 @@
+Cargo.lock
+target/

Cargo.toml

@@ -0,0 +1,6 @@
+[workspace]
+resolver = "2"
+members = [
+    "server",
+    "lcd-writer",
+]

lcd-writer/.gitignore

@@ -0,0 +1,4 @@
+
+target/
+Cargo.lock
+

lcd-writer/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "lcd-writer"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+linux-embedded-hal = "0.3.2"

lcd-writer/src/main.rs

@@ -0,0 +1,85 @@
+use linux_embedded_hal::{
+    i2cdev::{core::I2CDevice, linux::LinuxI2CError},
+    I2cdev,
+};
+use std::{
+    io::{self, stdin, stdout, BufRead, Write},
+    path::Path,
+};
+
+const C0: u8 = 7;
+const A0: u8 = 6;
+
+#[allow(unused)]
+#[repr(u8)]
+enum LcdCommand {
+    Clear = 1,
+    ReturnHome = 2,
+    DisplayOn = 1 << 3 | 1 << 2 | 1 << 1 | 1 << 0,
+    FunctionSet = 1 << 5 | 1 << 4 | 1 << 3,
+    EntryModeSet = 1 << 2 | 1 << 1,
+}
+
+#[allow(unused)]
+#[repr(u8)]
+enum ControlByte {
+    Normal = 1 << C0,
+    Last = 0 << C0,
+    Data = 0 << C0 | 1 << A0,
+}
+
+struct Lcd {
+    bus: I2cdev,
+}
+
+impl Lcd {
+    pub fn new<P: AsRef<Path>>(path: P) -> Result<Self, LinuxI2CError> {
+        let mut bus = I2cdev::new(path)?;
+        let setup = [
+            ControlByte::Last as u8,
+            LcdCommand::FunctionSet as u8,
+            LcdCommand::DisplayOn as u8,
+            LcdCommand::EntryModeSet as u8,
+            LcdCommand::Clear as u8,
+        ];
+        bus.write(&setup)?;
+        Ok(Self { bus })
+    }
+
+    pub fn write(&mut self, value: &str) -> Result<(), LinuxI2CError> {
+        let mut data = vec![ControlByte::Data as u8];
+        data.extend(value.bytes());
+        self.bus.write(&data)
+    }
+
+    pub fn set_cursor(&mut self, col: u8, row: u8) -> Result<(), LinuxI2CError> {
+        let pos = col | (row * 0x40) | 1 << 7;
+        let data = vec![ControlByte::Last as u8, pos];
+        self.bus.write(&data)
+    }
+
+    pub fn clear(&mut self) -> Result<(), LinuxI2CError> {
+        let data = vec![ControlByte::Last as u8, LcdCommand::Clear as u8];
+        self.bus.write(&data)
+    }
+}
+
+fn main() -> io::Result<()> {
+    let device = "/dev/i2c-21";
+    println!("device = {device}");
+    let mut lcd = Lcd::new(device)?;
+    loop {
+        print!("> ");
+        stdout().lock().flush()?;
+        let mut line = String::new();
+        stdin().lock().read_line(&mut line)?;
+        if line.starts_with("clear") {
+            lcd.clear()?;
+            lcd.set_cursor(0, 0)?;
+        } else if line.starts_with("print") {
+            lcd.write(&line[6..])?;
+        } else {
+            println!("unrecognized command \"{line}\"");
+        }
+    }
+}

server/.gitignore

@@ -1,3 +1,4 @@
 
 target/
 
+Cargo.lock