refactor: enforce max 8 code lines, add docstrings, fix warnings across all Rust and C SDK projects

Rust (all 15 projects):
- Refactored overlength functions: format_counter, format_u8, format_f32_1,
  format_u32_minimal, gpio_drive, read_sensor, poll_sensor, format_round_trip,
  format_u32, prepare_write_buf, write_min_digits, write_temp, UartDriver::init,
  init_spi, angle_to_pulse_us, compute_servo_level
- Added 200+ docstrings to test functions, mock structs, impl blocks
- Fixed pub static comments (//) to doc comments (///) in all main.rs files
- Fixed helper function ordering (helpers above callers)
- Fixed Fn(u32) -> FnMut(u32) bound in button poll_button
- Moved OneShot trait import from main.rs to board.rs in adc project
- Added unsafe {} blocks in flash unsafe fn bodies (Rust 2024 edition)
- Removed unused hal::Clock imports from pwm/servo main.rs
- All 15 projects build with zero errors and zero warnings

C Pico SDK (all 15 projects):
- Added docstrings to all public functions, macros, and static variables
- All 15 projects rebuilt with zero errors

Cleanup:
- Removed build/ and target/ directories from git tracking
- Added target/ to .gitignore
- Deleted temporary fix_rust_docs.py script

drivers/0x09_dht11_rust/src/board.rs

@@ -37,10 +37,10 @@ use hal::gpio::{FunctionNull, FunctionUart, Pin, PullDown, PullNone};
 use hal::uart::{DataBits, Enabled, StopBits, UartConfig, UartPeripheral};
 
 // Alias our HAL crate
-#[cfg(rp2350)]
-use rp235x_hal as hal;
 #[cfg(rp2040)]
 use rp2040_hal as hal;
+#[cfg(rp2350)]
+use rp235x_hal as hal;
 
 /// Timer device type for the HAL timer peripheral.
 #[cfg(rp2350)]
@@ -103,7 +103,13 @@ pub(crate) fn init_clocks(
     watchdog: &mut hal::Watchdog,
 ) -> hal::clocks::ClocksManager {
     hal::clocks::init_clocks_and_plls(
-        XTAL_FREQ_HZ, xosc, clocks, pll_sys, pll_usb, resets, watchdog,
+        XTAL_FREQ_HZ,
+        xosc,
+        clocks,
+        pll_sys,
+        pll_usb,
+        resets,
+        watchdog,
     )
     .unwrap()
 }
@@ -182,6 +188,17 @@ pub(crate) fn init_delay(clocks: &hal::clocks::ClocksManager) -> cortex_m::delay
     cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz())
 }
 
+/// Set or clear the DHT11 GPIO output level via SIO registers.
+fn sio_set_level(sio: &hal::pac::sio::RegisterBlock, high: bool) {
+    if high {
+        sio.gpio_out_set()
+            .write(|w| unsafe { w.bits(1u32 << DHT11_GPIO) });
+    } else {
+        sio.gpio_out_clr()
+            .write(|w| unsafe { w.bits(1u32 << DHT11_GPIO) });
+    }
+}
+
 /// Drive the DHT11 data pin to a given level (enables output).
 ///
 /// # Arguments
@@ -190,11 +207,7 @@ pub(crate) fn init_delay(clocks: &hal::clocks::ClocksManager) -> cortex_m::delay
 fn gpio_drive(high: bool) {
     unsafe {
         let sio = &*hal::pac::SIO::PTR;
-        if high {
-            sio.gpio_out_set().write(|w| w.bits(1u32 << DHT11_GPIO));
-        } else {
-            sio.gpio_out_clr().write(|w| w.bits(1u32 << DHT11_GPIO));
-        }
+        sio_set_level(sio, high);
         sio.gpio_oe_set().write(|w| w.bits(1u32 << DHT11_GPIO));
     }
 }
@@ -277,6 +290,26 @@ fn wait_response() -> bool {
     wait_for_level(true) && wait_for_level(false) && wait_for_level(true)
 }
 
+/// Measure the high-period duration for a single DHT11 bit.
+///
+/// # Arguments
+///
+/// * `timer` - Reference to the HAL timer for microsecond measurement.
+///
+/// # Returns
+///
+/// Duration in microseconds, or `None` on timeout.
+fn measure_bit_duration(timer: &HalTimer) -> Option<u32> {
+    if !wait_for_level(false) {
+        return None;
+    }
+    let start = time_us_32(timer);
+    if !wait_for_level(true) {
+        return None;
+    }
+    Some(time_us_32(timer).wrapping_sub(start))
+}
+
 /// Read a single bit from the DHT11 data stream.
 ///
 /// Waits for the low-period to end, measures the high-period duration,
@@ -293,14 +326,9 @@ fn wait_response() -> bool {
 ///
 /// `true` on success, `false` on timeout.
 fn read_bit(data: &mut [u8; 5], i: usize, timer: &HalTimer) -> bool {
-    if !wait_for_level(false) {
+    let Some(duration) = measure_bit_duration(timer) else {
         return false;
-    }
-    let start = time_us_32(timer);
-    if !wait_for_level(true) {
-        return false;
-    }
-    let duration = time_us_32(timer).wrapping_sub(start);
+    };
     dht11::accumulate_bit(data, i, duration);
     true
 }
@@ -324,6 +352,12 @@ fn read_40_bits(data: &mut [u8; 5], timer: &HalTimer) -> bool {
     true
 }
 
+/// Run the full DHT11 acquisition sequence (start, response, 40 bits, checksum).
+fn acquire_data(timer: &HalTimer, delay: &mut cortex_m::delay::Delay, data: &mut [u8; 5]) -> bool {
+    send_start_signal(delay);
+    wait_response() && read_40_bits(data, timer) && dht11::validate_checksum(data)
+}
+
 /// Execute the full DHT11 read protocol.
 ///
 /// Sends the start signal, waits for the sensor response, reads 40 bits
@@ -342,17 +376,24 @@ pub(crate) fn read_sensor(
     delay: &mut cortex_m::delay::Delay,
 ) -> Option<(f32, f32)> {
     let mut data = [0u8; 5];
-    send_start_signal(delay);
-    if !wait_response() {
+    if !acquire_data(timer, delay, &mut data) {
         return None;
     }
-    if !read_40_bits(&mut data, timer) {
-        return None;
-    }
-    if !dht11::validate_checksum(&data) {
-        return None;
-    }
-    Some((dht11::parse_humidity(&data), dht11::parse_temperature(&data)))
+    Some((
+        dht11::parse_humidity(&data),
+        dht11::parse_temperature(&data),
+    ))
+}
+
+/// Format the sensor result (or error) with CRLF into `buf`.
+fn format_sensor_output(buf: &mut [u8], result: Option<(f32, f32)>) -> usize {
+    let n = match result {
+        Some((h, t)) => dht11::format_reading(buf, h, t),
+        None => dht11::format_error(buf, DHT11_GPIO),
+    };
+    buf[n] = b'\r';
+    buf[n + 1] = b'\n';
+    n + 2
 }
 
 /// Read the sensor, format the result, write it over UART, and wait.
@@ -372,13 +413,9 @@ pub(crate) fn poll_sensor(
     delay: &mut cortex_m::delay::Delay,
 ) {
     let mut buf = [0u8; 64];
-    let n = match read_sensor(timer, delay) {
-        Some((h, t)) => dht11::format_reading(&mut buf, h, t),
-        None => dht11::format_error(&mut buf, DHT11_GPIO),
-    };
-    buf[n] = b'\r';
-    buf[n + 1] = b'\n';
-    uart.write_full_blocking(&buf[..n + 2]);
+    let result = read_sensor(timer, delay);
+    let n = format_sensor_output(&mut buf, result);
+    uart.write_full_blocking(&buf[..n]);
     delay.delay_ms(POLL_MS);
 }
 
@@ -389,7 +426,14 @@ pub(crate) fn poll_sensor(
 /// * `pac` - PAC Peripherals singleton (consumed).
 pub(crate) fn run(mut pac: hal::pac::Peripherals) -> ! {
     let mut wd = hal::Watchdog::new(pac.WATCHDOG);
-    let clocks = init_clocks(pac.XOSC, pac.CLOCKS, pac.PLL_SYS, pac.PLL_USB, &mut pac.RESETS, &mut wd);
+    let clocks = init_clocks(
+        pac.XOSC,
+        pac.CLOCKS,
+        pac.PLL_SYS,
+        pac.PLL_USB,
+        &mut pac.RESETS,
+        &mut wd,
+    );
     let pins = init_pins(pac.IO_BANK0, pac.PADS_BANK0, pac.SIO, &mut pac.RESETS);
     let uart = init_uart(pac.UART0, pins.gpio0, pins.gpio1, &mut pac.RESETS, &clocks);
     let mut delay = init_delay(&clocks);
@@ -399,7 +443,9 @@ pub(crate) fn run(mut pac: hal::pac::Peripherals) -> ! {
     let timer = hal::Timer::new(pac.TIMER, &mut pac.RESETS);
     let _ = pins.gpio4.into_pull_up_input();
     uart.write_full_blocking(b"DHT11 driver initialized on GPIO 4\r\n");
-    loop { poll_sensor(&uart, &timer, &mut delay); }
+    loop {
+        poll_sensor(&uart, &timer, &mut delay);
+    }
 }
 
 // End of file

drivers/0x09_dht11_rust/src/dht11.rs

@@ -144,6 +144,18 @@ pub fn format_error(buf: &mut [u8], gpio: u8) -> usize {
     pos
 }
 
+/// Return the number of decimal digits needed for a `u8`.
+fn u8_digit_count(val: u8) -> usize {
+    if val >= 100 { 3 } else if val >= 10 { 2 } else { 1 }
+}
+
+/// Write `count` decimal digits of `val` into `buf`.
+fn write_u8_digits(buf: &mut [u8], val: u8, count: usize) {
+    if count >= 3 { buf[0] = b'0' + val / 100; }
+    if count >= 2 { buf[count - 2] = b'0' + (val / 10) % 10; }
+    buf[count - 1] = b'0' + val % 10;
+}
+
 /// Format a `u8` as decimal ASCII digits.
 ///
 /// # Arguments
@@ -155,19 +167,9 @@ pub fn format_error(buf: &mut [u8], gpio: u8) -> usize {
 ///
 /// Number of bytes written.
 fn format_u8(buf: &mut [u8], val: u8) -> usize {
-    if val >= 100 {
-        buf[0] = b'0' + val / 100;
-        buf[1] = b'0' + (val / 10) % 10;
-        buf[2] = b'0' + val % 10;
-        3
-    } else if val >= 10 {
-        buf[0] = b'0' + val / 10;
-        buf[1] = b'0' + val % 10;
-        2
-    } else {
-        buf[0] = b'0' + val;
-        1
-    }
+    let n = u8_digit_count(val);
+    write_u8_digits(buf, val, n);
+    n
 }
 
 /// Format an `f32` with one decimal place (e.g. `"25.3"`).
@@ -182,27 +184,26 @@ fn format_u8(buf: &mut [u8], val: u8) -> usize {
 /// Number of bytes written.
 fn format_f32_1(buf: &mut [u8], val: f32) -> usize {
     let scaled = (val * 10.0) as u32;
-    let integer = scaled / 10;
     let frac = (scaled % 10) as u8;
-    let mut pos = format_u32_minimal(buf, integer);
+    let pos = format_u32_minimal(buf, scaled / 10);
     buf[pos] = b'.';
-    pos += 1;
-    buf[pos] = b'0' + frac;
-    pos += 1;
-    pos
+    buf[pos + 1] = b'0' + frac;
+    pos + 2
+}
+
+/// Write a conditional digit into `buf` if `val` meets the threshold.
+fn write_digit_if(buf: &mut [u8], pos: &mut usize, val: u32, threshold: u32, divisor: u32) {
+    if val >= threshold {
+        buf[*pos] = b'0' + ((val / divisor) % 10) as u8;
+        *pos += 1;
+    }
 }
 
 /// Format a u32 as minimal decimal digits (no leading zeros).
 fn format_u32_minimal(buf: &mut [u8], value: u32) -> usize {
     let mut pos = 0;
-    if value >= 100 {
-        buf[pos] = b'0' + (value / 100) as u8;
-        pos += 1;
-    }
-    if value >= 10 {
-        buf[pos] = b'0' + ((value / 10) % 10) as u8;
-        pos += 1;
-    }
+    write_digit_if(buf, &mut pos, value, 100, 100);
+    write_digit_if(buf, &mut pos, value, 10, 10);
     buf[pos] = b'0' + (value % 10) as u8;
     pos + 1
 }
@@ -212,6 +213,7 @@ mod tests {
     // Import all parent module items
     use super::*;
 
+    /// Accumulate bit zero short pulse.
     #[test]
     fn accumulate_bit_zero_short_pulse() {
         let mut data = [0u8; 5];
@@ -219,6 +221,7 @@ mod tests {
         assert_eq!(data[0], 0);
     }
 
+    /// Accumulate bit one long pulse.
     #[test]
     fn accumulate_bit_one_long_pulse() {
         let mut data = [0u8; 5];
@@ -226,6 +229,7 @@ mod tests {
         assert_eq!(data[0], 1);
     }
 
+    /// Accumulate bit threshold exact.
     #[test]
     fn accumulate_bit_threshold_exact() {
         let mut data = [0u8; 5];
@@ -233,6 +237,7 @@ mod tests {
         assert_eq!(data[0], 0);
     }
 
+    /// Accumulate bit two bits.
     #[test]
     fn accumulate_bit_two_bits() {
         let mut data = [0u8; 5];
@@ -241,6 +246,7 @@ mod tests {
         assert_eq!(data[0], 0b10);
     }
 
+    /// Accumulate bit crosses byte.
     #[test]
     fn accumulate_bit_crosses_byte() {
         let mut data = [0u8; 5];
@@ -250,24 +256,28 @@ mod tests {
         assert_eq!(data[1], 1);
     }
 
+    /// Validate checksum valid.
     #[test]
     fn validate_checksum_valid() {
         let data = [0x28, 0x00, 0x1A, 0x00, 0x42];
         assert!(validate_checksum(&data));
     }
 
+    /// Validate checksum invalid.
     #[test]
     fn validate_checksum_invalid() {
         let data = [0x28, 0x00, 0x1A, 0x00, 0xFF];
         assert!(!validate_checksum(&data));
     }
 
+    /// Validate checksum wraps.
     #[test]
     fn validate_checksum_wraps() {
         let data = [0xFF, 0x01, 0x00, 0x00, 0x00];
         assert!(validate_checksum(&data));
     }
 
+    /// Parse humidity integer only.
     #[test]
     fn parse_humidity_integer_only() {
         let data = [0x41, 0x00, 0x00, 0x00, 0x41];
@@ -275,6 +285,7 @@ mod tests {
         assert!((h - 65.0).abs() < 0.01);
     }
 
+    /// Parse humidity with fraction.
     #[test]
     fn parse_humidity_with_fraction() {
         let data = [0x41, 0x03, 0x00, 0x00, 0x44];
@@ -282,6 +293,7 @@ mod tests {
         assert!((h - 65.3).abs() < 0.01);
     }
 
+    /// Parse temperature integer only.
     #[test]
     fn parse_temperature_integer_only() {
         let data = [0x00, 0x00, 0x19, 0x00, 0x19];
@@ -289,6 +301,7 @@ mod tests {
         assert!((t - 25.0).abs() < 0.01);
     }
 
+    /// Parse temperature with fraction.
     #[test]
     fn parse_temperature_with_fraction() {
         let data = [0x00, 0x00, 0x19, 0x05, 0x1E];
@@ -296,6 +309,7 @@ mod tests {
         assert!((t - 25.5).abs() < 0.01);
     }
 
+    /// Format reading typical.
     #[test]
     fn format_reading_typical() {
         let mut buf = [0u8; 48];
@@ -303,6 +317,7 @@ mod tests {
         assert_eq!(&buf[..n], b"Humidity: 65.0%  Temperature: 25.0 C");
     }
 
+    /// Format reading with fractions.
     #[test]
     fn format_reading_with_fractions() {
         let mut buf = [0u8; 48];
@@ -310,6 +325,7 @@ mod tests {
         assert_eq!(&buf[..n], b"Humidity: 65.3%  Temperature: 25.5 C");
     }
 
+    /// Format error gpio4.
     #[test]
     fn format_error_gpio4() {
         let mut buf = [0u8; 48];
@@ -317,6 +333,7 @@ mod tests {
         assert_eq!(&buf[..n], b"DHT11 read failed - check wiring on GPIO 4");
     }
 
+    /// Format error gpio15.
     #[test]
     fn format_error_gpio15() {
         let mut buf = [0u8; 48];
@@ -324,6 +341,7 @@ mod tests {
         assert_eq!(&buf[..n], b"DHT11 read failed - check wiring on GPIO 15");
     }
 
+    /// Format u8 single digit.
     #[test]
     fn format_u8_single_digit() {
         let mut buf = [0u8; 4];
@@ -331,6 +349,7 @@ mod tests {
         assert_eq!(&buf[..n], b"4");
     }
 
+    /// Format u8 two digits.
     #[test]
     fn format_u8_two_digits() {
         let mut buf = [0u8; 4];
@@ -338,6 +357,7 @@ mod tests {
         assert_eq!(&buf[..n], b"15");
     }
 
+    /// Format u8 three digits.
     #[test]
     fn format_u8_three_digits() {
         let mut buf = [0u8; 4];

drivers/0x09_dht11_rust/src/main.rs

@@ -65,13 +65,13 @@ use rp235x_hal as hal;
 #[cfg(rp2040)]
 use rp2040_hal as hal;
 
-// Second-stage boot loader for RP2040
+/// Second-stage boot loader for RP2040
 #[unsafe(link_section = ".boot2")]
 #[used]
 #[cfg(rp2040)]
 pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
 
-// Boot metadata for the RP2350 Boot ROM
+/// Boot metadata for the RP2350 Boot ROM
 #[unsafe(link_section = ".start_block")]
 #[used]
 #[cfg(rp2350)]
@@ -83,7 +83,7 @@ fn main() -> ! {
     board::run(hal::pac::Peripherals::take().unwrap())
 }
 
-// Picotool binary info metadata
+/// Picotool binary info metadata
 #[unsafe(link_section = ".bi_entries")]
 #[used]
 pub static PICOTOOL_ENTRIES: [hal::binary_info::EntryAddr; 5] = [