Add Arm Cortex-M0+ delayer

docs/delayer.md

@@ -0,0 +1,8 @@
+# Blocking Delay Facilities
+The `::picolibrary::Arm::Cortex::M0PLUS::Delayer` blocking delay nullary functor is
+defined in the
+[`include/picolibrary/arm/cortex/m0plus/delayer.h`](https://github.com/apcountryman/picolibrary-arm-cortex-m0plus/blob/main/include/picolibrary/arm/cortex/m0plus/delayer.h)/`source/picolibrary/arm/cortex/m0plus/delayer.cc`](https://github.com/apcountryman/picolibrary-arm-cortex-m0plus/blob/main/source/picolibrary/arm/cortex/m0plus/delayer.cc)
+header/source file pair.
+`::picolibrary::Arm::Cortex::M0PLUS::Delayer` supports the following operations:
+- To delay, use the `::picolibrary::Arm::Cortex::M0PLUS::Delayer::operator()()` member
+  function.

docs/index.md

@@ -9,3 +9,4 @@
 1. [Library Configuration](library_configuration.md)
 1. [Peripheral Facilities](peripheral.md)
 1. [Interrupt Facilities](interrupt.md)
+1. [Blocking Delay Facilities](delayer.md)

include/picolibrary/arm/cortex/m0plus/delayer.h

@@ -0,0 +1,144 @@
+/**
+ * picolibrary-arm-cortex-m0plus
+ *
+ * Copyright 2023, Andrew Countryman <apcountryman@gmail.com> and the
+ * picolibrary-arm-cortex-m0plus contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this
+ * file except in compliance with the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under
+ * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+/**
+ * \file
+ * \brief picolibrary::Arm::Cortex::M0PLUS::Delayer interface.
+ */
+
+#ifndef PICOLIBRARY_ARM_CORTEX_M0PLUS_DELAYER_H
+#define PICOLIBRARY_ARM_CORTEX_M0PLUS_DELAYER_H
+
+#include <cstdint>
+
+#include "picolibrary/arm/cortex/m0plus/peripheral/systick.h"
+#include "picolibrary/utility.h"
+
+namespace picolibrary::Arm::Cortex::M0PLUS {
+
+/**
+ * \brief Blocking delayer.
+ */
+class Delayer {
+  public:
+    /**
+     * \brief SYSTICK clock source.
+     */
+    enum class Clock_Source : std::uint32_t {
+        EXTERNAL_REFERENCE_CLOCK = 0 << Peripheral::SYSTICK::CSR::Bit::CLKSOURCE, ///< External reference clock.
+        PROCESSOR_CLOCK = 1 << Peripheral::SYSTICK::CSR::Bit::CLKSOURCE, ///< Processor clock.
+    };
+
+    /**
+     * \brief Constructor.
+     */
+    constexpr Delayer() noexcept = default;
+
+    /**
+     * \brief Constructor.
+     *
+     * \param[in] systick The SYSTICK peripheral instance to use to create blocking
+     *            delays.
+     * \param[in] clock_source The SYSTICK peripheral clock source to use.
+     * \param[in] reload_value The SYSTICK peripheral counter reload value to use to
+     *            create blocking delays of the desired duration.
+     *
+     * \attention The delayer will use processor clock if the external reference clock is
+     *            requested but is not available.
+     */
+    constexpr Delayer( Peripheral::SYSTICK & systick, Clock_Source clock_source, std::uint32_t reload_value ) noexcept
+        :
+        m_systick{ &systick }
+    {
+        m_systick->rvr = reload_value;
+        m_systick->cvr = 0;
+        m_systick->csr = to_underlying( clock_source ) | Peripheral::SYSTICK::CSR::Mask::ENABLE;
+    }
+
+    /**
+     * \brief Constructor.
+     *
+     * \param[in] source The source of the move.
+     */
+    constexpr Delayer( Delayer && source ) noexcept : m_systick{ source.m_systick }
+    {
+        source.m_systick = nullptr;
+    }
+
+    Delayer( Delayer const & ) = delete;
+
+    /**
+     * \brief Destructor.
+     */
+    ~Delayer() noexcept
+    {
+        disable();
+    }
+
+    /**
+     * \brief Assignment operator.
+     *
+     * \param[in] expression The expression to be assigned.
+     *
+     * \return The assigned to object.
+     */
+    constexpr auto operator=( Delayer && expression ) noexcept -> Delayer &
+    {
+        if ( &expression != this ) {
+            disable();
+
+            m_systick = expression.m_systick;
+
+            expression.m_systick = nullptr;
+        } // if
+
+        return *this;
+    }
+
+    auto operator=( Delayer const & ) = delete;
+
+    /**
+     * \brief Delay.
+     */
+    void operator()() const noexcept
+    {
+        m_systick->cvr = 0;
+
+        while ( not( m_systick->csr & Peripheral::SYSTICK::CSR::Mask::COUNTFLAG ) ) {} // while
+    }
+
+  private:
+    /**
+     * \brief The SYSTICK peripheral instance used to create blocking delays.
+     */
+    Peripheral::SYSTICK * m_systick{};
+
+    /**
+     * \brief Disable the counter.
+     */
+    constexpr void disable() noexcept
+    {
+        if ( m_systick ) {
+            m_systick->rvr = 0;
+            m_systick->csr = 0;
+        } // if
+    }
+};
+
+} // namespace picolibrary::Arm::Cortex::M0PLUS
+
+#endif // PICOLIBRARY_ARM_CORTEX_M0PLUS_DELAYER_H

source/CMakeLists.txt

@@ -25,6 +25,7 @@ set(
     PICOLIBRARY_ARM_CORTEX_M0PLUS_SOURCE_FILES
     "picolibrary/arm/cortex/m0plus.cc"
     "picolibrary/arm/cortex/m0plus/configuration.cc"
+    "picolibrary/arm/cortex/m0plus/delayer.cc"
     "picolibrary/arm/cortex/m0plus/interrupt.cc"
     "picolibrary/arm/cortex/m0plus/peripheral.cc"
     "picolibrary/arm/cortex/m0plus/peripheral/mpu.cc"

source/picolibrary/arm/cortex/m0plus/delayer.cc

@@ -0,0 +1,23 @@
+/**
+ * picolibrary-arm-cortex-m0plus
+ *
+ * Copyright 2023, Andrew Countryman <apcountryman@gmail.com> and the
+ * picolibrary-arm-cortex-m0plus contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this
+ * file except in compliance with the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under
+ * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+/**
+ * \file
+ * \brief picolibrary::Arm::Cortex::M0PLUS::Delayer implementation.
+ */
+
+#include "picolibrary/arm/cortex/m0plus/delayer.h"