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// RustDuino : A generic HAL implementation for Arduino Boards in Rust
// Copyright (C) 2021 Shivam Malhotra, Indian Institute of Technology Kanpur
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>

//! Source code to set the clock frequency for the current AVR micro-controller
//! also if no micro-controller environment found than the value is set to a
//! resonable default value.

#[allow(unused_imports)]
use const_env__value::value_from_env;

/// The clock frequency of the current AVR microcontroller (if the `cpu-frequency` crate feature is
/// enabled).
///
/// This value is set at compilation time.
///
/// This value is derived from the `$AVR_CPU_FREQUENCY_HZ` environment variable.
///
/// When this crate is compiled for a non-AVR target, this value simply becomes
/// a reasonable default.
pub const CPU_FREQUENCY_HZ: u32 = CPU_FREQUENCY_HZ_IMPL;

/// The default CPU frequency to assume when AVR is not being targeted.
/// This allows the crate to work for tests, and allows generating without
/// targeting AVR.
#[allow(dead_code)]
const DEFAULT_CPU_FREQUENCY_WHEN_NOT_AVR_HZ: u32 = 16_000_000;

#[cfg(target_arch = "avr")]
// N.B. the comment on the end of the next line is there because it will be seen in the compiler diagnostic.
const CPU_FREQUENCY_HZ_IMPL: u32 = value_from_env!("AVR_CPU_FREQUENCY_HZ": u32); // Must be set whenever AVR is being targeted.
#[cfg(not(target_arch = "avr"))]
const CPU_FREQUENCY_HZ_IMPL: u32 = DEFAULT_CPU_FREQUENCY_WHEN_NOT_AVR_HZ;

#[cfg(test)]
mod test {
    #[test]
    fn cpu_frequency_is_nonzero() {
        assert!(crate::config::CPU_FREQUENCY_HZ > 0);
    }
}