1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166

//! `rust-mcp3008` is a rewrite of the excellent [Adafruit_Python_MCP3008](https://github.com/adafruit/Adafruit_Python_MCP3008) Python library in Rust.

#[cfg(test)]
mod tests {
    use super::Mcp3008;
    use std::path::Path;
    use std::env;

    #[test]
    fn mcp3008_read_adc() {
        let spi_dev_path = "/dev/spidev0.0";

        if cfg!(target_os = "linux") {
            if Path::new(&spi_dev_path).exists() {
                let mut mcp3008 = Mcp3008::new(spi_dev_path).unwrap();

                mcp3008.read_adc(0).unwrap();

                if let Ok(_) = mcp3008.read_adc(8) {
                    panic!("read from adc > 7");
                }
            } else {
                if let Ok(_) = env::var("TRAVIS_RUST_VERSION") {
                    println!("can't mock spi interface on travis, passing test...");
                } else {
                    panic!("can not test on current setup (no spi interface)");
                }
            }
        } else {
            panic!("can not test on current setup (unsupported os)");
        }
    }
}

#[cfg(target_os = "linux")]
extern crate spidev;

use std::io;
use std::fmt;
use std::error::Error;

#[cfg(target_os = "linux")]
use spidev::{SPI_MODE_0, Spidev, SpidevOptions, SpidevTransfer};

#[derive(Debug)]
pub enum Mcp3008Error {
    SpidevError(io::Error),
    AdcOutOfRangeError(u8),
    UnsupportedOSError,
}

impl fmt::Display for Mcp3008Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Mcp3008Error::SpidevError(ref err) => err.fmt(f),
            Mcp3008Error::AdcOutOfRangeError(adc_number) => {
                write!(f, "invalid adc number ({})", adc_number)
            }
            Mcp3008Error::UnsupportedOSError => write!(f, "unsupported os"),
        }
    }
}

impl Error for Mcp3008Error {
    fn description(&self) -> &str {
        match *self {
            Mcp3008Error::SpidevError(ref err) => err.description(),
            Mcp3008Error::AdcOutOfRangeError(_) => "invalid adc number",
            Mcp3008Error::UnsupportedOSError => "unsupported os",
        }
    }

    fn cause(&self) -> Option<&Error> {
        match *self {
            Mcp3008Error::SpidevError(ref err) => Some(err),
            Mcp3008Error::AdcOutOfRangeError(_) => None,
            Mcp3008Error::UnsupportedOSError => None,
        }
    }
}

impl From<io::Error> for Mcp3008Error {
    fn from(err: io::Error) -> Mcp3008Error {
        Mcp3008Error::SpidevError(err)
    }
}

pub struct Mcp3008 {
    #[cfg(target_os = "linux")]
    spi: Spidev,
}

/// Provides access to a MCP3008 A/D converter.
/// # Example
///
/// ```rust
/// extern crate mcp3008;
///
/// use mcp3008::Mcp3008;
///
/// fn main() {
///     if let Ok(mut mcp3008) = Mcp3008::new("/dev/spidev0.0") {
///         println!("{}", mcp3008.read_adc(0).unwrap());
///     }
/// }
/// ```
impl Mcp3008 {
    /// Constructs a new `Mcp3008`.
    #[cfg(target_os = "linux")]
    pub fn new(spi_dev_path: &str) -> Result<Mcp3008, Mcp3008Error> {
        let options = SpidevOptions::new()
            .max_speed_hz(1_000_000)
            .mode(SPI_MODE_0)
            .lsb_first(false)
            .build();

        let mut spi = Spidev::open(spi_dev_path.to_string())?;

        match spi.configure(&options) {
            Ok(_) => Ok(Mcp3008 { spi: spi }),
            Err(err) => Err(Mcp3008Error::SpidevError(err)),
        }
    }

    #[cfg(not(target_os = "linux"))]
    pub fn new(_spi_dev_path: &str) -> Result<Mcp3008, Mcp3008Error> {
        Err(Mcp3008Error::UnsupportedOSError)
    }

    #[cfg(target_os = "linux")]
    pub fn read_adc(&mut self, adc_number: u8) -> Result<u16, Mcp3008Error> {
        match adc_number {
            0...7 => {
                // Start bit, single channel read
                let mut command: u8 = 0b11 << 6;
                command |= (adc_number & 0x07) << 3;
                // Bottom 3 bits of command are 0, this is to account for the
                // extra clock to do the conversion, and the low null bit returned
                // at the start of the response.

                let tx_buf = [command, 0x0, 0x0];
                let mut rx_buf = [0_u8; 3];

                // Marked as own scope so that rx_buf isn't borrowed
                // anymore after the transfer() call
                {
                    let mut transfer = SpidevTransfer::read_write(&tx_buf, &mut rx_buf);

                    self.spi.transfer(&mut transfer)?;
                }

                let mut result = (rx_buf[0] as u16 & 0x01) << 9;
                result |= (rx_buf[1] as u16 & 0xFF) << 1;
                result |= (rx_buf[2] as u16 & 0x80) >> 7;

                Ok(result & 0x3FF)
            }
            _ => Err(Mcp3008Error::AdcOutOfRangeError(adc_number)),
        }
    }

    #[cfg(not(target_os = "linux"))]
    pub fn read_adc(&mut self, _adc_number: u8) -> Result<u16, Mcp3008Error> {
        Err(Mcp3008Error::UnsupportedOSError)
    }
}