Port HD44780 display example from rp2040-hal to rp-pico (#347)

boards/rp-pico/Cargo.toml

@@ -33,6 +33,7 @@ smart-leds = "0.3.0"
 ws2812-pio = { git = "https://github.com/ithinuel/ws2812-pio-rs", rev = "fd6b6604d65a66242b52ccf7f24a95ca325991dd" }
 ssd1306 = "0.7.0"
 embedded-graphics = "0.7.1"
+hd44780-driver = "0.4.0"
 
 defmt = "0.2.0"
 defmt-rtt = "0.2.0"

boards/rp-pico/examples/pico_hd44780_display.rs

@@ -0,0 +1,138 @@
+//! # LCD Display Example
+//!
+//! In this example, the RP2040 is configured to drive a small two-line
+//! alphanumeric LCD using the
+//! [HD44780](https://crates.io/crates/hd44780-driver) driver.
+//!
+//! This example drives the LCD by pushing data out of six GPIO pins, writing
+//! the data four bits at a time. A faster alternative can be created using
+//! HD44780::new_8bit() but requiring an additional four GPIO pins.
+//!
+//! See the `Cargo.toml` file for Copyright and license details.
+//!
+//! ```text
+//!                      /--------------------------------------\
+//!  ____________        |        /-------------------------\   |
+//! | 1       GND|-------+---\    |           _|USB|_       |   |
+//! | 2       VDD|-------+---+----/          |1  R 40|-VBUS-o   v
+//! | 3        VS|-------/   |               |2  P 39|       ||POT||
+//! | 4        RS|--\        o-----------GND-|3    38|-GND----------o
+//! | 5        RW|--+--------/    /------GP2-|4  P 37|
+//! | 6        EN|--+-\        /--+------GP3-|5  I 36|
+//! | 7          |  | |     /--+--+------GP4-|6  C   |
+//! | 8          |  | |  /--+--+--+------GP5-|7  O   |
+//! | 9          |  | \--+--+--+--+---\      |8      |
+//! | 10         |  \----+--+--+--+-\  \-GP6-|9      |
+//! | 11       D4|-------/  |  |  |  \---GP7-|10     |
+//! | 12       D5|----------/  |  |          .........
+//! | 13       D6|-------------/  |          |20   21|
+//! | 14       D7|----------------/           """""""
+//! ..............
+//! Symbols:
+//!     - (+) crossing lines, not connected
+//!     - (o) connected lines
+//! ```
+//!
+//! See the `Cargo.toml` file for Copyright and license details.
+
+#![no_std]
+#![no_main]
+
+// The macro for our start-up function
+use cortex_m_rt::entry;
+
+// Ensure we halt the program on panic (if we don't mention this crate it won't
+// be linked)
+use panic_halt as _;
+
+// Pull in any important traits
+use rp_pico::hal::prelude::*;
+
+// GPIO traits
+use embedded_hal::digital::v2::OutputPin;
+
+// Time handling traits
+use embedded_time::rate::*;
+
+// For LCD display
+use hd44780_driver::HD44780;
+
+#[entry]
+fn main() -> ! {
+    // Grab our singleton objects
+    let mut pac = rp_pico::hal::pac::Peripherals::take().unwrap();
+    let core = rp_pico::hal::pac::CorePeripherals::take().unwrap();
+
+    // Set up the watchdog driver - needed by the clock setup code
+    let mut watchdog = rp_pico::hal::Watchdog::new(pac.WATCHDOG);
+
+    // Configure the clocks
+    // The default is to generate a 125 MHz system clock
+    let clocks = rp_pico::hal::clocks::init_clocks_and_plls(
+        rp_pico::XOSC_CRYSTAL_FREQ,
+        pac.XOSC,
+        pac.CLOCKS,
+        pac.PLL_SYS,
+        pac.PLL_USB,
+        &mut pac.RESETS,
+        &mut watchdog,
+    )
+    .ok()
+    .unwrap();
+
+    // The single-cycle I/O block controls our GPIO pins
+    let sio = rp_pico::hal::Sio::new(pac.SIO);
+
+    // Set the pins up according to their function on this particular board
+    let pins = rp_pico::Pins::new(
+        pac.IO_BANK0,
+        pac.PADS_BANK0,
+        sio.gpio_bank0,
+        &mut pac.RESETS,
+    );
+
+    let mut led_pin = pins.led.into_push_pull_output();
+
+    // The delay object lets us wait for specified amounts of time
+    let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
+
+    // Init pins
+    let rs = pins.gpio7.into_push_pull_output();
+    let en = pins.gpio6.into_push_pull_output();
+    let d4 = pins.gpio5.into_push_pull_output();
+    let d5 = pins.gpio4.into_push_pull_output();
+    let d6 = pins.gpio3.into_push_pull_output();
+    let d7 = pins.gpio2.into_push_pull_output();
+
+    // LCD Init
+    let mut lcd = HD44780::new_4bit(rs, en, d4, d5, d6, d7, &mut delay).unwrap();
+
+    loop {
+        // Clear the screen
+        lcd.reset(&mut delay).unwrap();
+        lcd.clear(&mut delay).unwrap();
+
+        // Write to the top line
+        lcd.write_str("rp-hal on", &mut delay).unwrap();
+
+        // Move the cursor
+        lcd.set_cursor_pos(40, &mut delay).unwrap();
+
+        // Write more more text
+        lcd.write_str("HD44780! ", &mut delay).unwrap();
+        let mut char_count = 9;
+        for ch in "move along!.. ".chars() {
+            if char_count > 15 {
+                // Switch autoscroll on
+                lcd.set_autoscroll(true, &mut delay).unwrap();
+            }
+            led_pin.set_high().unwrap();
+            lcd.write_char(ch, &mut delay).unwrap();
+            char_count += 1;
+            delay.delay_us(400_000); //0.4s
+            led_pin.set_low().unwrap();
+            delay.delay_us(100_000); //0.1s
+        }
+        lcd.set_autoscroll(false, &mut delay).unwrap();
+    }
+}