some small improvements

firmware/rust1/src/bin/heizung.rs

@@ -72,7 +72,12 @@ fn format_scan_result<const N : usize>(msg : &mut String<N>, scan_result : [Scan
     Ok(())
 }
 
-async fn _clockStretch<'d, SCL: gpio::Pin>(scl: &mut Flex<'d, SCL>) -> Result<(), i2c::Error> {
+
+// adapted from arduino-pico:
+// https://github.com/earlephilhower/arduino-pico/blob/6e52b72523b11470b2ad2b0578ca1500be238108/libraries/Wire/src/Wire.cpp#L257
+// This seems to be the only way to do zero-length writes:
+// see https://github.com/raspberrypi/pico-sdk/issues/238
+async fn handle_clock_stretching<'d, SCL: gpio::Pin>(scl: &mut Flex<'d, SCL>) -> Result<(), i2c::Error> {
     use i2c::Error::*;
     use i2c::AbortReason::*;
 
@@ -88,26 +93,24 @@ async fn _clockStretch<'d, SCL: gpio::Pin>(scl: &mut Flex<'d, SCL>) -> Result<()
         Second(_) => Err(Abort(ArbitrationLoss)),
     }
 }
-
-// adapted from https://github.com/earlephilhower/arduino-pico/blob/6e52b72523b11470b2ad2b0578ca1500be238108/libraries/Wire/src/Wire.cpp#L257
 async fn i2c_write_zero_bytes_middle_part<'d, SCL: gpio::Pin, SDA: gpio::Pin, const FREQ : u64>(
         mut addr: u16, delay: Duration, scl: &mut Flex<'d, SCL>, sda: &mut Flex<'d, SDA>)
         -> Result<(), i2c::Error> {
     sda.set_as_input();
     Timer::after(delay).await;
     scl.set_as_input();
-    _clockStretch(scl).await?;
+    handle_clock_stretching(scl).await?;
     sda.set_as_output();
     Timer::after(delay).await;
     scl.set_as_output();
     Timer::after(delay).await;
-    for i in 0..8 {
+    for _ in 0..8 {
         addr <<= 1;
         sda.set_level(if (addr & (1 << 7)) != 0 { gpio::Level::High } else { gpio::Level::Low });
         Timer::after(delay).await;
         scl.set_as_input();
         Timer::after(delay).await;
-        _clockStretch(scl).await?;
+        handle_clock_stretching(scl).await?;
         scl.set_as_output();
         Timer::after(Duration::from_micros(5)).await; // Ensure we don't change too close to clock edge
     }
@@ -115,7 +118,7 @@ async fn i2c_write_zero_bytes_middle_part<'d, SCL: gpio::Pin, SDA: gpio::Pin, co
     sda.set_as_input();
     Timer::after(delay).await;
     scl.set_as_input();
-    _clockStretch(scl).await?;
+    handle_clock_stretching(scl).await?;
 
     let result = if sda.is_low() {
         Ok(())
@@ -129,13 +132,12 @@ async fn i2c_write_zero_bytes_middle_part<'d, SCL: gpio::Pin, SDA: gpio::Pin, co
 
     result
 }
-async fn i2c_write_zero_bytes<SCL: gpio::Pin, SDA: gpio::Pin, const FREQ : u64>(mut addr: u16, scl: &mut SCL, sda: &mut SDA)
+async fn i2c_write_zero_bytes<SCL: gpio::Pin, SDA: gpio::Pin, const FREQ : u64>(addr: u16, scl: &mut SCL, sda: &mut SDA)
         -> Result<(), i2c::Error> {
     use i2c::Error::*;
     use i2c::AbortReason::*;
 
     let delay = Duration::from_micros((1000000 / FREQ) / 2);
-    let ack = false;
 
     let mut sda = Flex::new(sda);
     let mut scl = Flex::new(scl);
@@ -181,18 +183,13 @@ async fn i2c_task(mut i2c_peri: embassy_rp::peripherals::I2C0,
         const MAX_ADDRESS : u8 = 128;
         let mut scan_result = [ScanResult::Error; MAX_ADDRESS as usize];
         for i in 0..MAX_ADDRESS {
-            match i2c_write_zero_bytes::<_, _, 400_000>(i as u16, &mut scl, &mut sda).await {
-                Result::Ok(()) => {
-                    //info!("I2C ok: {}", i);
-                    scan_result[i as usize] = ScanResult::Ack
-                },
-                Result::Err(Abort(NoAcknowledge)) =>
-                    scan_result[i as usize] = ScanResult::NAck,
-                    Result::Err(AddressReserved(_)) =>
-                        scan_result[i as usize] = ScanResult::Reserved,
+            scan_result[i as usize] = match i2c_write_zero_bytes::<_, _, 400_000>(i as u16, &mut scl, &mut sda).await {
+                Result::Ok(()) => ScanResult::Ack,
+                Result::Err(Abort(NoAcknowledge)) => ScanResult::NAck,
+                Result::Err(AddressReserved(_)) => ScanResult::Reserved,
                 Result::Err(e) => {
-                    scan_result[i as usize] = ScanResult::Error;
-                    warn!("I2C problem: {:?}", e);
+                    warn!("I2C problem: {:02x}: {:?}", i, e);
+                    ScanResult::Error
                 }
             }
         }