From 37fb18c9ef0dda81c3fe82b16a1b6256eb3b2d5b Mon Sep 17 00:00:00 2001
From: Jihyun Yu <yjh0502@gmail.com>
Date: Sun, 19 Apr 2020 21:12:55 +0900
Subject: [PATCH] initial CRC support

---
 examples/crc.rs | 27 +++++++++++++++++++++++++++
 src/crc.rs      | 39 +++++++++++++++++++++++++++++++++++++++
 src/lib.rs      |  2 ++
 src/prelude.rs  |  7 ++++---
 4 files changed, 72 insertions(+), 3 deletions(-)
 create mode 100644 examples/crc.rs
 create mode 100644 src/crc.rs

diff --git a/examples/crc.rs b/examples/crc.rs
new file mode 100644
index 00000000..da58af53
--- /dev/null
+++ b/examples/crc.rs
@@ -0,0 +1,27 @@
+//! CRC calculation
+
+#![deny(unsafe_code)]
+#![no_main]
+#![no_std]
+
+use panic_halt as _;
+
+use cortex_m_rt::entry;
+use cortex_m_semihosting::hprintln;
+use stm32f1xx_hal::{pac, prelude::*};
+
+#[entry]
+fn main() -> ! {
+    let p = pac::Peripherals::take().unwrap();
+
+    let mut rcc = p.RCC.constrain();
+    let mut crc = p.CRC.new(&mut rcc.ahb);
+
+    crc.reset();
+    crc.write(0x12345678);
+
+    let val = crc.read();
+    hprintln!("found={:08x}, expected={:08x}", val, 0xdf8a8a2bu32).ok();
+
+    loop {}
+}
diff --git a/src/crc.rs b/src/crc.rs
new file mode 100644
index 00000000..6d99b99b
--- /dev/null
+++ b/src/crc.rs
@@ -0,0 +1,39 @@
+//! CRC
+
+use crate::pac::CRC;
+use crate::rcc::{Enable, AHB};
+
+/// Extension trait to constrain the CRC peripheral
+pub trait CrcExt {
+    /// Constrains the CRC peripheral to play nicely with the other abstractions
+    fn new(self, ahb: &mut AHB) -> Crc;
+}
+
+impl CrcExt for CRC {
+    fn new(self, ahb: &mut AHB) -> Crc {
+        CRC::enable(ahb);
+        Crc { crc: self }
+    }
+}
+
+/// Constrained CRC peripheral
+pub struct Crc {
+    crc: CRC,
+}
+
+impl Crc {
+    pub fn read(&self) -> u32 {
+        self.crc.dr.read().bits()
+    }
+
+    pub fn write(&mut self, val: u32) {
+        unsafe { self.crc.dr.write(|w| w.bits(val)) }
+    }
+
+    pub fn reset(&self) {
+        self.crc.cr.write(|w| w.reset().set_bit());
+        // calling CRC::dr::write() just after CRC::cr::reset() will not work as expected, and
+        // inserting single nop() seems to solve the problem.
+        cortex_m::asm::nop();
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 49319bd2..543f1556 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -106,6 +106,8 @@ pub mod backup_domain;
 #[cfg(feature = "device-selected")]
 pub mod bb;
 #[cfg(feature = "device-selected")]
+pub mod crc;
+#[cfg(feature = "device-selected")]
 pub mod delay;
 #[cfg(feature = "device-selected")]
 pub mod dma;
diff --git a/src/prelude.rs b/src/prelude.rs
index a6691ab1..ff349473 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -1,6 +1,10 @@
 pub use crate::adc::ChannelTimeSequence as _stm32_hal_adc_ChannelTimeSequence;
 pub use crate::afio::AfioExt as _stm32_hal_afio_AfioExt;
+pub use crate::crc::CrcExt as _stm32_hal_crc_CrcExt;
+pub use crate::dma::CircReadDma as _stm32_hal_dma_CircReadDma;
 pub use crate::dma::DmaExt as _stm32_hal_dma_DmaExt;
+pub use crate::dma::ReadDma as _stm32_hal_dma_ReadDma;
+pub use crate::dma::WriteDma as _stm32_hal_dma_WriteDma;
 pub use crate::flash::FlashExt as _stm32_hal_flash_FlashExt;
 pub use crate::gpio::GpioExt as _stm32_hal_gpio_GpioExt;
 pub use crate::hal::adc::OneShot as _embedded_hal_adc_OneShot;
@@ -8,7 +12,4 @@ pub use crate::hal::digital::v2::StatefulOutputPin as _embedded_hal_digital_Stat
 pub use crate::hal::digital::v2::ToggleableOutputPin as _embedded_hal_digital_ToggleableOutputPin;
 pub use crate::hal::prelude::*;
 pub use crate::rcc::RccExt as _stm32_hal_rcc_RccExt;
-pub use crate::dma::CircReadDma as _stm32_hal_dma_CircReadDma;
-pub use crate::dma::ReadDma as _stm32_hal_dma_ReadDma;
-pub use crate::dma::WriteDma as _stm32_hal_dma_WriteDma;
 pub use crate::time::U32Ext as _stm32_hal_time_U32Ext;