Showcase i2c writing from linux

red/Cargo.toml

@@ -10,6 +10,7 @@ bytes = "1.2.1"
 euclid = "0.22.7"
 futures = "0.3.24"
 gilrs = "0.10.1"
+i2c-linux = "0.1.2"
 lazy_static = "1.4.0"
 regex = "1.6.0"
 tokio = { version = "1.21.0", features = ["full"] }

red/src/main.rs

@@ -1,18 +1,58 @@
 #![warn(rust_2018_idioms)]
 use futures::never::Never;
+use i2c_linux::I2c;
 use red::jogger;
 use red::printer::gcode::*;
 use red::printer::Printer;
 use std::time::Duration;
 
 const DEFAULT_TTY: &str = "/dev/ttyUSB0";
+const I2C_ADDRESS_EXTENDER: u8 = 25;
+const I2C_REGISTER_SPINDLE_SPEED: u8 = 0;
+
+// available i2c functionality on the device as reported from
+// the i2c library
+//  TENBIT_ADDR
+//  SMBUS_PEC
+//  SMBUS_QUICK
+//  SMBUS_READ_BYTE
+//  SMBUS_WRITE_BYTE
+//  SMBUS_READ_BYTE_DATA
+//  SMBUS_WRITE_BYTE_DATA
+//  SMBUS_READ_WORD_DATA
+//  SMBUS_WRITE_WORD_DATA
+//  SMBUS_PROC_CALL
+//  SMBUS_WRITE_BLOCK_DATA
+//  SMBUS_READ_I2C_BLOCK
+//  SMBUS_WRITE_I2C_BLOCK
+//  SMBUS_BYTE
+//  SMBUS_BYTE_DATA
+//  SMBUS_WORD_DATA
+//  SMBUS_I2C_BLOCK
+//  SMBUS_EMUL
 
 #[tokio::main]
 async fn main() -> Never {
-    communicate().await
+    write_to_spindle().await
 }
 
-async fn communicate() -> Never {
+async fn write_to_spindle() -> Never {
+    let mut i2c = I2c::from_path("/dev/i2c-0").unwrap();
+    let mut value = 0;
+    println!("functionality: {:?}", i2c.i2c_functionality());
+    i2c.smbus_set_slave_address(I2C_ADDRESS_EXTENDER.into(), false)
+        .unwrap();
+    loop {
+        value = u16::MAX - value;
+        match i2c.smbus_write_word_data(I2C_REGISTER_SPINDLE_SPEED, value) {
+            Ok(()) => println!("Wrote {} successfully", value),
+            Err(e) => println!("Error writing to device: {}", e),
+        };
+        tokio::time::sleep(Duration::from_secs(1)).await;
+    }
+}
+
+async fn write_to_printer() -> Never {
     let mut printer = Printer::connect(DEFAULT_TTY).await.unwrap();
     printer
         .send_gcode(Box::new(M114Command::new()))