pw_analog/public/pw_analog/analog_input.h

// Copyright 2021 The Pigweed Authors
//
// 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
//
//     https://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.
#pragma once

#include "pw_chrono/system_clock.h"
#include "pw_result/result.h"

namespace pw::analog {

/// Base interface for getting analog-to-digital (ADC) samples from one ADC
/// channel in a thread-safe manner.
///
/// The ADC backend interface is up to the user to define and implement for now.
/// This gives flexibility for the ADC driver implementation.
///
/// `AnalogInput` controls a specific input / channel where the ADC peripheral
/// may be shared across multiple channels that may be controlled by multiple
/// threads. The implementer of this pure virtual interface is responsible for
/// ensuring thread safety and access at the driver level.
class AnalogInput {
 public:
  /// Specifies the sample range.
  /// These values do not change at runtime.
  struct Limits {
    /// The minimum of the sample range.
    int32_t min;
    /// The maximum of the sample range.
    int32_t max;
  };

  virtual ~AnalogInput() = default;

  /// Blocks until the specified timeout duration has elapsed or the ADC sample
  /// has been returned, whichever comes first.
  ///
  /// This method is thread safe.
  ///
  /// @returns
  /// * A sample on success.
  /// * @pw_status{RESOURCE_EXHAUSTED} - ADC peripheral in use.
  /// * @pw_status{DEADLINE_EXCEEDED} - Timed out waiting for a sample.
  /// * Other statuses left up to the implementer.
  Result<int32_t> TryReadFor(chrono::SystemClock::duration timeout) {
    return TryReadUntil(chrono::SystemClock::TimePointAfterAtLeast(timeout));
  }

  /// Blocks until the deadline time has been reached or the ADC sample
  /// has been returned, whichever comes first.
  ///
  /// This method is thread safe.
  ///
  /// @returns
  /// * A sample on success.
  /// * @pw_status{RESOURCE_EXHAUSTED} - ADC peripheral in use.
  /// * @pw_status{DEADLINE_EXCEEDED} - Timed out waiting for a sample.
  /// * Other statuses left up to the implementer.
  virtual Result<int32_t> TryReadUntil(
      chrono::SystemClock::time_point deadline) = 0;

  /// @returns The range of the ADC sample. These values do not change at
  /// runtime.
  virtual Limits GetLimits() const = 0;
};

}  // namespace pw::analog