From 0afda7192c30a16ca14dc15939b0a0ccb9fceecc Mon Sep 17 00:00:00 2001
From: Adam Macdonald <72780006+twokilohertz@users.noreply.github.com>
Date: Thu, 20 Feb 2025 14:06:46 +0000
Subject: [PATCH] Hello, UART

---
 Cargo.lock       |  1 +
 Cargo.toml       |  1 +
 src/constants.rs |  2 ++
 src/main.rs      | 36 +++++++++++++++++++++++-------------
 4 files changed, 27 insertions(+), 13 deletions(-)
 create mode 100644 src/constants.rs

diff --git a/Cargo.lock b/Cargo.lock
index 10985ee..a6b49fe 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -263,6 +263,7 @@ name = "pico-enviro-sensor"
 version = "0.1.0"
 dependencies = [
  "embedded-hal 1.0.0",
+ "fugit",
  "panic-halt",
  "rp235x-hal",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index b470140..a84cab0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,6 +9,7 @@ edition = "2021"
 
 [dependencies]
 embedded-hal = "1.0.0"
+fugit = "0.3.7"
 panic-halt = "1.0.0"
 rp235x-hal = { version = "0.2.0", features = [
     "critical-section-impl",
diff --git a/src/constants.rs b/src/constants.rs
new file mode 100644
index 0000000..3141208
--- /dev/null
+++ b/src/constants.rs
@@ -0,0 +1,2 @@
+/// Pico 2 W on-board crystal oscillator frequency (AEL 12.0)
+pub const XTAL_FREQ_HZ: u32 = 12_000_000u32;
diff --git a/src/main.rs b/src/main.rs
index 5e33c9c..cd5cd11 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,22 +1,26 @@
 #![no_std]
 #![no_main]
 
-use panic_halt as _;
+use embedded_hal::delay::DelayNs;
+use fugit::RateExtU32;
+use panic_halt as _; // Needed so its built & linked correctly
 
 // Alias for our HAL crate
 use rp235x_hal as hal;
 
-// Some things we need
-use embedded_hal::delay::DelayNs;
-use embedded_hal::digital::OutputPin;
+// RP235x HAL
+use hal::uart::DataBits;
+use hal::uart::StopBits;
+use hal::uart::UartConfig;
+use hal::uart::UartPeripheral;
+use hal::Clock;
+
+mod constants;
 
 #[link_section = ".start_block"]
 #[used]
 pub static IMAGE_DEF: hal::block::ImageDef = hal::block::ImageDef::secure_exe();
 
-/// Pico 2 W on-board crystal oscillator frequency (AEL 12.0)
-const XTAL_FREQ_HZ: u32 = 12_000_000u32;
-
 #[hal::entry]
 fn main() -> ! {
     let mut peripherals = hal::pac::Peripherals::take().unwrap();
@@ -24,7 +28,7 @@ fn main() -> ! {
     let mut watchdog = hal::Watchdog::new(peripherals.WATCHDOG);
 
     let clocks = hal::clocks::init_clocks_and_plls(
-        XTAL_FREQ_HZ,
+        constants::XTAL_FREQ_HZ,
         peripherals.XOSC,
         peripherals.CLOCKS,
         peripherals.PLL_SYS,
@@ -45,12 +49,18 @@ fn main() -> ! {
         &mut peripherals.RESETS,
     );
 
-    let mut led_pin = pins.gpio19.into_push_pull_output();
+    let uart0_pins = (pins.gpio0.into_function(), pins.gpio1.into_function());
+
+    let uart = UartPeripheral::new(peripherals.UART0, uart0_pins, &mut peripherals.RESETS)
+        .enable(
+            UartConfig::new(9600_u32.Hz(), DataBits::Eight, None, StopBits::One),
+            clocks.peripheral_clock.freq(),
+        )
+        .unwrap();
+
     loop {
-        led_pin.set_high().unwrap();
-        timer.delay_ms(1000);
-        led_pin.set_low().unwrap();
-        timer.delay_ms(1000);
+        uart.write_full_blocking(b"hello, world!\r\n");
+        timer.delay_ms(500);
     }
 }