wip

Cargo.lock

@@ -36,6 +36,13 @@ version = "0.2.153"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
 
+[[package]]
+name = "linux_realtime"
+version = "0.1.0"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "nix"
 version = "0.28.0"
@@ -54,6 +61,7 @@ version = "0.1.0"
 dependencies = [
  "interrupts",
  "libc",
+ "linux_realtime",
  "rppal",
 ]
 

Cargo.toml

@@ -10,3 +10,6 @@ rppal = "0.17.1"
 #rumqttc = "0.24.0"
 interrupts = "0.1.5"
 libc = "0.2.153"
+
+[dependencies.linux_realtime]
+path = "../linux_realtime"

src/dht11.rs

@@ -1,8 +1,4 @@
-use std::{
-    error::Error,
-    thread,
-    time::{Duration, Instant},
-};
+use std::{error::Error, time::Duration};
 
 use rppal::gpio::Gpio;
 
@@ -19,45 +15,47 @@ impl Dht11Sensor {
         Ok(Dht11Sensor { pin })
     }
 
-    fn expect_pulse(&mut self, expected_level: bool) -> Result<Duration, Box<dyn Error>> {
-        let started = Instant::now();
+    fn expect_pulse(&mut self, expected_level: bool) -> Result<u32, Box<dyn Error>> {
+        let _guard = interrupts::disable();
+        let mut count: u32 = 0;
+        let mut rtclock = linux_realtime::Clock::new()?;
         loop {
             if self.pin.is_high() != expected_level {
                 break;
             }
-            if started.elapsed() >= Duration::from_micros(1000) {
+            if count >= 1000 {
                 return Err(std::io::Error::new(
                     std::io::ErrorKind::InvalidData,
                     "Timeout while reading pulse",
                 )
                 .into());
             }
-
-            thread::sleep(Duration::from_micros(1));
+            count += 1;
+            rtclock.sleep(Duration::from_micros(1))?;
         }
-        Ok(started.elapsed())
+        Ok(count)
     }
 
     pub fn read(&mut self) -> Result<Dht11Data, Box<dyn Error>> {
         use rppal::gpio::{Bias, Mode};
 
         let mut data = [0; 5];
-        let mut cycles: [Duration; 80] = [Duration::from_micros(0); 80];
+        let mut cycles: [u32; 80] = [0; 80];
 
-        let guard = interrupts::disable();
+        let mut rtclock = linux_realtime::Clock::new()?;
 
         self.pin.set_mode(Mode::Input);
         self.pin.set_bias(Bias::PullUp);
-        thread::sleep(Duration::from_millis(1));
+        rtclock.sleep(Duration::from_millis(1))?;
 
         self.pin.set_mode(Mode::Output);
         self.pin.set_low();
-        thread::sleep(Duration::from_millis(20));
+        rtclock.sleep(Duration::from_millis(20))?;
 
         // Timing Critical Code
         self.pin.set_mode(Mode::Input);
         self.pin.set_bias(Bias::PullUp);
-        thread::sleep(Duration::from_micros(55));
+        rtclock.sleep(Duration::from_micros(55))?;
 
         self.expect_pulse(false)?;
         self.expect_pulse(true)?;

src/main.rs

@@ -1,15 +1,21 @@
-use std::{error::Error, thread, time::Duration};
+use std::{error::Error, time::Duration};
 
 use dht11::Dht11Sensor;
+use linux_realtime::ThreadAttributes;
 
 mod dht11;
 
 fn main() -> Result<(), Box<dyn Error>> {
-    unsafe {
-        libc::setpriority(libc::PRIO_PROCESS, 0, -20);
-    }
     let mut sensor = Dht11Sensor::new(2)?;
+    let t = linux_realtime::JoinHandle::spawn(
+        ThreadAttributes {
+            stack_size: libc::PTHREAD_STACK_MIN,
+            scheduler_policy: linux_realtime::SchedulerPolicy::Fifo,
+            thread_priority: 99,
+        },
+        move || -> Result<(), Box<dyn Error>> {
             loop {
+                let mut rtclock = linux_realtime::Clock::new()?;
                 match sensor.read() {
                     Ok(data) => println!(
                         "Humidity: {}; Temperature: {}",
@@ -17,8 +23,13 @@ fn main() -> Result<(), Box<dyn Error>> {
                     ),
                     Err(msg) => println!("Error: {}", msg),
                 }
-        thread::sleep(Duration::from_millis(2000));
+                for n in 1..10 {
+                    rtclock.sleep(Duration::from_millis(500))?;
+                }
             }
+        },
+    )?;
+    _ = t.join();
 
     Ok(())
 }