feat: add 0x08_lcd1602_rust driver with 14 unit tests

2026-05-27 01:32:25 +02:00 · 2026-03-25 17:31:05 -04:00
parent b0299bf95e
commit c68e158f16
18 changed files with 1639 additions and 0 deletions
@@ -0,0 +1,143 @@
+/// PCF8574 -> LCD control pin: Register Select.
+pub const PIN_RS: u8 = 0x01;
+
+/// PCF8574 -> LCD control pin: Read/Write.
+pub const PIN_RW: u8 = 0x02;
+
+/// PCF8574 -> LCD control pin: Enable.
+pub const PIN_EN: u8 = 0x04;
+
+/// Build a PCF8574 output byte for a 4-bit LCD nibble.
+pub fn build_nibble(nibble: u8, nibble_shift: u8, mode: u8, backlight_mask: u8) -> u8 {
+    let mut data = (nibble & 0x0F) << nibble_shift;
+    if mode != 0 { data |= PIN_RS; }
+    data |= backlight_mask;
+    data
+}
+
+/// Build the PCF8574 byte with EN asserted.
+pub fn nibble_with_en(nibble_byte: u8) -> u8 {
+    nibble_byte | PIN_EN
+}
+
+/// Build the PCF8574 byte with EN de-asserted.
+pub fn nibble_without_en(nibble_byte: u8) -> u8 {
+    nibble_byte & !PIN_EN
+}
+
+/// HD44780 row-offset lookup.
+const ROW_OFFSETS: [u8; 2] = [0x00, 0x40];
+
+/// Compute the DDRAM address byte for `lcd_set_cursor`.
+pub fn cursor_address(line: u8, position: u8) -> u8 {
+    let row = if line > 1 { 1 } else { line as usize };
+    0x80 | (position + ROW_OFFSETS[row])
+}
+
+/// Format a counter value as `"Count: NNNNNN"` (right-justified, 6 digits).
+pub fn format_counter(buf: &mut [u8], count: u32) -> usize {
+    let prefix = b"Count: ";
+    buf[..7].copy_from_slice(prefix);
+    let mut pos = 7;
+    let digits = [
+        ((count / 100000) % 10) as u8,
+        ((count / 10000) % 10) as u8,
+        ((count / 1000) % 10) as u8,
+        ((count / 100) % 10) as u8,
+        ((count / 10) % 10) as u8,
+        (count % 10) as u8,
+    ];
+    let mut leading = true;
+    for (i, &d) in digits.iter().enumerate() {
+        if i == 5 || d != 0 { leading = false; }
+        buf[pos] = if leading { b' ' } else { b'0' + d };
+        pos += 1;
+    }
+    pos
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn build_nibble_command_mode() {
+        let b = build_nibble(0x03, 4, 0, 0x08);
+        assert_eq!(b, 0x38);
+    }
+
+    #[test]
+    fn build_nibble_data_mode() {
+        let b = build_nibble(0x04, 4, 1, 0x08);
+        assert_eq!(b, 0x49);
+    }
+
+    #[test]
+    fn build_nibble_no_backlight() {
+        let b = build_nibble(0x0F, 4, 0, 0x00);
+        assert_eq!(b, 0xF0);
+    }
+
+    #[test]
+    fn nibble_with_en_sets_bit() {
+        assert_eq!(nibble_with_en(0x38), 0x3C);
+    }
+
+    #[test]
+    fn nibble_without_en_clears_bit() {
+        assert_eq!(nibble_without_en(0x3C), 0x38);
+    }
+
+    #[test]
+    fn cursor_address_line0_col0() {
+        assert_eq!(cursor_address(0, 0), 0x80);
+    }
+
+    #[test]
+    fn cursor_address_line1_col0() {
+        assert_eq!(cursor_address(1, 0), 0xC0);
+    }
+
+    #[test]
+    fn cursor_address_line0_col5() {
+        assert_eq!(cursor_address(0, 5), 0x85);
+    }
+
+    #[test]
+    fn cursor_address_line1_col15() {
+        assert_eq!(cursor_address(1, 15), 0xCF);
+    }
+
+    #[test]
+    fn cursor_address_clamps_line() {
+        assert_eq!(cursor_address(5, 0), 0xC0);
+    }
+
+    #[test]
+    fn format_counter_zero() {
+        let mut buf = [0u8; 16];
+        let n = format_counter(&mut buf, 0);
+        assert_eq!(&buf[..n], b"Count:      0");
+    }
+
+    #[test]
+    fn format_counter_one() {
+        let mut buf = [0u8; 16];
+        let n = format_counter(&mut buf, 1);
+        assert_eq!(&buf[..n], b"Count:      1");
+    }
+
+    #[test]
+    fn format_counter_large() {
+        let mut buf = [0u8; 16];
+        let n = format_counter(&mut buf, 123456);
+        assert_eq!(&buf[..n], b"Count: 123456");
+    }
+
+    #[test]
+    fn format_counter_six_digits() {
+        let mut buf = [0u8; 16];
+        let n = format_counter(&mut buf, 999999);
+        assert_eq!(&buf[..n], b"Count: 999999");
+    }
+}
@@ -0,0 +1,3 @@
+#![no_std]
+
+pub mod lcd1602;
@@ -0,0 +1,326 @@
+//! @file main.rs
+//! @brief HD44780 16x2 LCD (PCF8574 I2C backpack) demonstration
+//! @author Kevin Thomas
+//! @date 2025
+//!
+//! MIT License
+//!
+//! Copyright (c) 2025 Kevin Thomas
+//!
+//! Permission is hereby granted, free of charge, to any person obtaining a copy
+//! of this software and associated documentation files (the "Software"), to deal
+//! in the Software without restriction, including without limitation the rights
+//! to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//! copies of the Software, and to permit persons to whom the Software is
+//! furnished to do so, subject to the following conditions:
+//!
+//! The above copyright notice and this permission notice shall be included in
+//! all copies or substantial portions of the Software.
+//!
+//! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//! IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//! FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//! AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//! LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//! OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//! SOFTWARE.
+//!
+//! -----------------------------------------------------------------------------
+//!
+//! Demonstrates 16x2 HD44780 LCD connected via a PCF8574 I2C backpack using
+//! the lcd1602 driver (lcd1602.rs). Line 0 shows a static title and line 1
+//! displays a live up-counter that increments every second. The counter
+//! value is also printed over UART for debugging.
+//!
+//! Wiring:
+//!   GPIO2 (SDA) -> PCF8574 backpack SDA  (4.7 kohm pull-up to 3.3 V)
+//!   GPIO3 (SCL) -> PCF8574 backpack SCL  (4.7 kohm pull-up to 3.3 V)
+//!   3.3V or 5V  -> PCF8574 backpack VCC
+//!   GND         -> PCF8574 backpack GND
+
+#![no_std]
+#![no_main]
+
+#[allow(dead_code)]
+mod lcd1602;
+
+use defmt_rtt as _;
+#[cfg(target_arch = "riscv32")]
+use panic_halt as _;
+#[cfg(target_arch = "arm")]
+use panic_probe as _;
+
+use embedded_hal::i2c::I2c;
+use fugit::RateExtU32;
+use hal::entry;
+use hal::Clock;
+use hal::gpio::{FunctionI2C, FunctionNull, FunctionUart, Pin, PullDown, PullNone, PullUp};
+use hal::uart::{DataBits, Enabled, StopBits, UartConfig, UartPeripheral};
+
+#[cfg(rp2350)]
+use rp235x_hal as hal;
+
+#[cfg(rp2040)]
+use rp2040_hal as hal;
+
+#[unsafe(link_section = ".boot2")]
+#[used]
+#[cfg(rp2040)]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
+
+#[unsafe(link_section = ".start_block")]
+#[used]
+#[cfg(rp2350)]
+pub static IMAGE_DEF: hal::block::ImageDef = hal::block::ImageDef::secure_exe();
+
+const XTAL_FREQ_HZ: u32 = 12_000_000u32;
+
+const UART_BAUD: u32 = 115_200;
+const I2C_BAUD: u32 = 100_000;
+const LCD_I2C_ADDR: u8 = 0x27;
+const NIBBLE_SHIFT: u8 = 4;
+const BACKLIGHT_MASK: u8 = 0x08;
+const COUNTER_DELAY_MS: u32 = 1_000;
+
+type TxPin = Pin<hal::gpio::bank0::Gpio0, FunctionUart, PullNone>;
+type RxPin = Pin<hal::gpio::bank0::Gpio1, FunctionUart, PullNone>;
+type TxPinDefault = Pin<hal::gpio::bank0::Gpio0, FunctionNull, PullDown>;
+type RxPinDefault = Pin<hal::gpio::bank0::Gpio1, FunctionNull, PullDown>;
+type EnabledUart = UartPeripheral<Enabled, hal::pac::UART0, (TxPin, RxPin)>;
+
+/// Initialise system clocks and PLLs from the external 12 MHz crystal.
+///
+/// # Arguments
+///
+/// * `xosc` - XOSC peripheral singleton.
+/// * `clocks` - CLOCKS peripheral singleton.
+/// * `pll_sys` - PLL_SYS peripheral singleton.
+/// * `pll_usb` - PLL_USB peripheral singleton.
+/// * `resets` - Mutable reference to the RESETS peripheral.
+/// * `watchdog` - Mutable reference to the watchdog timer.
+///
+/// # Returns
+///
+/// Configured clocks manager.
+///
+/// # Panics
+///
+/// Panics if clock initialisation fails.
+fn init_clocks(
+    xosc: hal::pac::XOSC,
+    clocks: hal::pac::CLOCKS,
+    pll_sys: hal::pac::PLL_SYS,
+    pll_usb: hal::pac::PLL_USB,
+    resets: &mut hal::pac::RESETS,
+    watchdog: &mut hal::Watchdog,
+) -> hal::clocks::ClocksManager {
+    hal::clocks::init_clocks_and_plls(
+        XTAL_FREQ_HZ, xosc, clocks, pll_sys, pll_usb, resets, watchdog,
+    )
+    .unwrap()
+}
+
+/// Unlock the GPIO bank and return the pin set.
+///
+/// # Arguments
+///
+/// * `io_bank0` - IO_BANK0 peripheral singleton.
+/// * `pads_bank0` - PADS_BANK0 peripheral singleton.
+/// * `sio` - SIO peripheral singleton.
+/// * `resets` - Mutable reference to the RESETS peripheral.
+///
+/// # Returns
+///
+/// GPIO pin set for the entire bank.
+fn init_pins(
+    io_bank0: hal::pac::IO_BANK0,
+    pads_bank0: hal::pac::PADS_BANK0,
+    sio: hal::pac::SIO,
+    resets: &mut hal::pac::RESETS,
+) -> hal::gpio::Pins {
+    let sio = hal::Sio::new(sio);
+    hal::gpio::Pins::new(io_bank0, pads_bank0, sio.gpio_bank0, resets)
+}
+
+/// Initialise UART0 for serial output (stdio equivalent).
+///
+/// # Arguments
+///
+/// * `uart0` - PAC UART0 peripheral singleton.
+/// * `tx_pin` - GPIO pin to use as UART0 TX (GPIO 0).
+/// * `rx_pin` - GPIO pin to use as UART0 RX (GPIO 1).
+/// * `resets` - Mutable reference to the RESETS peripheral.
+/// * `clocks` - Reference to the initialised clock configuration.
+///
+/// # Returns
+///
+/// Enabled UART0 peripheral ready for blocking writes.
+///
+/// # Panics
+///
+/// Panics if the HAL cannot achieve the requested baud rate.
+fn init_uart(
+    uart0: hal::pac::UART0,
+    tx_pin: TxPinDefault,
+    rx_pin: RxPinDefault,
+    resets: &mut hal::pac::RESETS,
+    clocks: &hal::clocks::ClocksManager,
+) -> EnabledUart {
+    let pins = (
+        tx_pin.reconfigure::<FunctionUart, PullNone>(),
+        rx_pin.reconfigure::<FunctionUart, PullNone>(),
+    );
+    let cfg = UartConfig::new(UART_BAUD.Hz(), DataBits::Eight, None, StopBits::One);
+    UartPeripheral::new(uart0, pins, resets)
+        .enable(cfg, clocks.peripheral_clock.freq())
+        .unwrap()
+}
+
+/// Create a blocking delay timer from the ARM SysTick peripheral.
+///
+/// # Arguments
+///
+/// * `clocks` - Reference to the initialised clock configuration.
+///
+/// # Returns
+///
+/// Blocking delay provider.
+///
+/// # Panics
+///
+/// Panics if the cortex-m core peripherals have already been taken.
+fn init_delay(clocks: &hal::clocks::ClocksManager) -> cortex_m::delay::Delay {
+    let core = cortex_m::Peripherals::take().unwrap();
+    cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz())
+}
+
+/// Write one raw byte to the PCF8574 expander over I2C.
+fn pcf_write_byte(i2c: &mut impl I2c, addr: u8, data: u8) {
+    let _ = i2c.write(addr, &[data]);
+}
+
+/// Toggle EN to latch a nibble into the LCD controller.
+fn pcf_pulse_enable(i2c: &mut impl I2c, addr: u8, data: u8, delay: &mut cortex_m::delay::Delay) {
+    pcf_write_byte(i2c, addr, lcd1602::nibble_with_en(data));
+    delay.delay_us(1);
+    pcf_write_byte(i2c, addr, lcd1602::nibble_without_en(data));
+    delay.delay_us(50);
+}
+
+/// Write one 4-bit nibble to the LCD.
+fn lcd_write4(i2c: &mut impl I2c, addr: u8, nibble: u8, mode: u8, delay: &mut cortex_m::delay::Delay) {
+    let data = lcd1602::build_nibble(nibble, NIBBLE_SHIFT, mode, BACKLIGHT_MASK);
+    pcf_pulse_enable(i2c, addr, data, delay);
+}
+
+/// Send one full 8-bit command/data value as two nibbles.
+fn lcd_send(i2c: &mut impl I2c, addr: u8, value: u8, mode: u8, delay: &mut cortex_m::delay::Delay) {
+    lcd_write4(i2c, addr, (value >> 4) & 0x0F, mode, delay);
+    lcd_write4(i2c, addr, value & 0x0F, mode, delay);
+}
+
+/// Execute the HD44780 4-bit mode power-on reset sequence.
+fn lcd_hd44780_reset(i2c: &mut impl I2c, addr: u8, delay: &mut cortex_m::delay::Delay) {
+    lcd_write4(i2c, addr, 0x03, 0, delay);
+    delay.delay_ms(5);
+    lcd_write4(i2c, addr, 0x03, 0, delay);
+    delay.delay_us(150);
+    lcd_write4(i2c, addr, 0x03, 0, delay);
+    delay.delay_us(150);
+    lcd_write4(i2c, addr, 0x02, 0, delay);
+    delay.delay_us(150);
+}
+
+/// Send post-reset configuration commands to the HD44780.
+fn lcd_hd44780_configure(i2c: &mut impl I2c, addr: u8, delay: &mut cortex_m::delay::Delay) {
+    lcd_send(i2c, addr, 0x28, 0, delay);
+    lcd_send(i2c, addr, 0x0C, 0, delay);
+    lcd_send(i2c, addr, 0x01, 0, delay);
+    delay.delay_ms(2);
+    lcd_send(i2c, addr, 0x06, 0, delay);
+}
+
+/// Set the LCD cursor position.
+fn lcd_set_cursor(i2c: &mut impl I2c, addr: u8, line: u8, position: u8, delay: &mut cortex_m::delay::Delay) {
+    lcd_send(i2c, addr, lcd1602::cursor_address(line, position), 0, delay);
+}
+
+/// Write a byte slice as character data to the LCD.
+fn lcd_puts(i2c: &mut impl I2c, addr: u8, s: &[u8], delay: &mut cortex_m::delay::Delay) {
+    for &ch in s {
+        lcd_send(i2c, addr, ch, 1, delay);
+    }
+}
+
+/// Initialize the LCD, display the title, and log over UART.
+fn setup_display(
+    i2c: &mut impl I2c,
+    uart: &EnabledUart,
+    delay: &mut cortex_m::delay::Delay,
+) {
+    lcd_hd44780_reset(i2c, LCD_I2C_ADDR, delay);
+    lcd_hd44780_configure(i2c, LCD_I2C_ADDR, delay);
+    lcd_set_cursor(i2c, LCD_I2C_ADDR, 0, 0, delay);
+    lcd_puts(i2c, LCD_I2C_ADDR, b"Reverse Eng.", delay);
+    uart.write_full_blocking(b"LCD 1602 driver initialized at I2C addr 0x27\r\n");
+}
+
+/// Format and display the next counter value on LCD line 1.
+fn update_counter(
+    i2c: &mut impl I2c,
+    uart: &EnabledUart,
+    delay: &mut cortex_m::delay::Delay,
+    count: &mut u32,
+) {
+    let mut buf = [0u8; 16];
+    let n = lcd1602::format_counter(&mut buf, *count);
+    *count += 1;
+    lcd_set_cursor(i2c, LCD_I2C_ADDR, 1, 0, delay);
+    lcd_puts(i2c, LCD_I2C_ADDR, &buf[..n], delay);
+    uart.write_full_blocking(&buf[..n]);
+    uart.write_full_blocking(b"\r\n");
+    delay.delay_ms(COUNTER_DELAY_MS);
+}
+
+/// Application entry point for the LCD 1602 counter demo.
+///
+/// Initializes the LCD over I2C with a static title on line 0 and
+/// continuously increments a counter on line 1 every second.
+///
+/// # Returns
+///
+/// Does not return.
+#[entry]
+fn main() -> ! {
+    let mut pac = hal::pac::Peripherals::take().unwrap();
+    let clocks = init_clocks(
+        pac.XOSC, pac.CLOCKS, pac.PLL_SYS, pac.PLL_USB, &mut pac.RESETS,
+        &mut hal::Watchdog::new(pac.WATCHDOG),
+    );
+    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);
+    let sda_pin = pins.gpio2.reconfigure::<FunctionI2C, PullUp>();
+    let scl_pin = pins.gpio3.reconfigure::<FunctionI2C, PullUp>();
+    let mut i2c = hal::I2C::i2c1(
+        pac.I2C1, sda_pin, scl_pin, I2C_BAUD.Hz(),
+        &mut pac.RESETS, clocks.system_clock.freq(),
+    );
+    setup_display(&mut i2c, &uart, &mut delay);
+    let mut count: u32 = 0;
+    loop {
+        update_counter(&mut i2c, &uart, &mut delay, &mut count);
+    }
+}
+
+#[unsafe(link_section = ".bi_entries")]
+#[used]
+pub static PICOTOOL_ENTRIES: [hal::binary_info::EntryAddr; 5] = [
+    hal::binary_info::rp_cargo_bin_name!(),
+    hal::binary_info::rp_cargo_version!(),
+    hal::binary_info::rp_program_description!(c"LCD 1602 Counter Demo"),
+    hal::binary_info::rp_cargo_homepage_url!(),
+    hal::binary_info::rp_program_build_attribute!(),
+];
+
+// End of file