Add debug info when motors or sensor not connected

src/display.rs

@@ -21,6 +21,30 @@ pub enum Parameter {
     Speed,
 }
 
+#[allow(clippy::similar_names)]
+pub fn draw_debug<'a>(screen: &mut Screen, text: impl IntoIterator<Item = &'a str>, font: &Font) {
+    #[allow(clippy::cast_precision_loss)]
+    let scale = Scale {
+        x: screen.xres() as f32 / 10.0,
+        y: screen.yres() as f32 / 4.0 - 8.0,
+    };
+    let xres = i32::try_from(screen.xres()).expect("range checked");
+    let yres = i32::try_from(screen.yres()).expect("range checked");
+    let center = xres / 2;
+    clear(screen);
+    for (i, line) in text.into_iter().enumerate().take(4) {
+        draw_centered_text(
+            screen,
+            center,
+            yres * i32::try_from(i).expect("there is only place for 4 lines") / 4 + 4,
+            scale,
+            font,
+            line,
+        );
+    }
+    screen.update();
+}
+
 #[allow(clippy::similar_names)]
 pub fn draw_calibration(screen: &mut Screen, parameter: &str, value: impl Display, font: &Font) {
     #[allow(clippy::cast_precision_loss)]

src/main.rs

@@ -2,25 +2,43 @@ mod buttons;
 mod display;
 
 use buttons::SmartEv3Buttons;
-use display::{draw_calibration, draw_driving, draw_finished, draw_settings, font, Parameter};
-use ev3dev_lang_rust::{motors::LargeMotor, sensors::ColorSensor, Ev3Error, Ev3Result, Screen};
+use display::{
+    draw_calibration, draw_debug, draw_driving, draw_finished, draw_settings, font, Parameter,
+};
+use ev3dev_lang_rust::{
+    motors::LargeMotor, sensors::ColorSensor, Device, Ev3Error, Ev3Result, Screen,
+};
 use pid::Pid;
 use rand::{thread_rng, Rng};
 use rusttype::Font;
 use std::{
     error::Error,
+    iter,
     thread::sleep,
     time::{Duration, Instant},
 };
 use thiserror::Error;
 
-fn main() -> Result<(), Box<dyn Error>> {
-    let motors = LargeMotor::list()?;
-    let [right_motor, left_motor] = &motors[..] else {println!("motors: {motors:?}"); Err("need two motors")?};
-    let sensor = ColorSensor::find()?;
-    let mut buttons = SmartEv3Buttons::new()?;
-    let mut screen = Screen::new()?;
+fn main() {
+    while try_main().is_err() {
+        sleep(Duration::from_millis(10));
+    }
+}
+
+fn try_main() -> Result<(), Box<dyn Error>> {
     let font = font();
+    let mut screen = Screen::new()?;
+    let motors = LargeMotor::list()?;
+    let [right_motor, left_motor] = &motors[..] else {
+        let motor_texts: Vec<_> = motors.iter().map(|motor| format!("{:?}", motor.get_driver_name())).collect();
+        draw_debug(&mut screen, iter::once("motors:").chain(motor_texts.iter().map(String::as_str)), &font);
+        Err("need two motors")?
+    };
+    let sensor = ColorSensor::find().map_err(|e| {
+        draw_debug(&mut screen, ["no color sensor"], &font);
+        e
+    })?;
+    let mut buttons = SmartEv3Buttons::new()?;
 
     left_motor.set_polarity(LargeMotor::POLARITY_INVERSED)?;
     right_motor.set_polarity(LargeMotor::POLARITY_INVERSED)?;