mcp3424 0.3.0

Async Rust driver for the MCP3422/3/4 ADC.
Documentation 
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

use crate::cfg::Cfg;
use crate::{mode, Error};
use core::marker::PhantomData;
use core::ops::Not;
use embedded_hal_async::i2c::SevenBitAddress;

/// Driver for the MCP342[2/3/4].
///
/// Depending on the enabled crate features and the specified [`mode::Mode`], there are different measure
/// functions available.
///
/// # See also
/// [`mode::ContinuousMode`], [`mode::MultiShotMode`], [`mode::OneShotMode`]
///
pub struct MCP3424<I2c, BusError, Delay, Mode> {
    pub(crate) i2c: I2c,
    pub(crate) address: u8,
    pub(crate) delay: Delay,
    pub(crate) mode: Mode,
    _phantom: PhantomData<BusError>
}

impl <I2c, BusError, Delay, Mode> MCP3424<I2c, BusError, Delay, Mode>
where
    I2c: embedded_hal_async::i2c::I2c,
    BusError: embedded_hal_async::i2c::Error,
    Delay: embedded_hal_async::delay::DelayNs,
    Error<BusError>: From<<I2c as embedded_hal_async::i2c::ErrorType>::Error>,
    Mode: mode::Mode
{
    const REFERENCE_VOLTAGE: i64 = 2_048_000_000;
    const REFERENCE_VOLTAGE_X2: i64 = Self::REFERENCE_VOLTAGE * 2;

    pub fn new(i2c: I2c, address: SevenBitAddress, delay: Delay, mode: Mode) -> Self {
        Self {
            i2c,
            address,
            delay,
            mode,
            _phantom: PhantomData,
        }
    }

    pub(crate) async fn read(&mut self, read: &mut [u8]) -> Result<(), I2c::Error> {
        self.i2c.read(self.address, read).await
    }

    pub(crate) async fn write(&mut self, write: &[u8]) -> Result<(), I2c::Error> {
        self.i2c.write(self.address, write).await
    }

    pub(crate) fn convert(buffer: &[u8; 4]) -> Result<f32, Error<BusError>> {

        let cfg = if buffer[3] & 0b1100 == 0b1100 {
            Cfg::from(buffer[3])
        }
        else {
            Cfg::from(buffer[2])
        };

        if cfg.ready.not() {
            return Err(Error::NotReady)
        }

        let value = {
            let mut value = 0_u32;
            for i in 0..cfg.resolution.bytes() {
                value <<= 8;
                value |= buffer[i] as u32
            }
            if value & cfg.resolution.sign_bit() != 0 {
                value |= cfg.resolution.sign_extend()
            }
            value as i32
        };

        let min = cfg.resolution.min();
        let max = cfg.resolution.max();

        if value > min && value < max {
            Ok((value as i64 * Self::REFERENCE_VOLTAGE_X2 / (1 << cfg.resolution.bits())) as f32 / (1_000_000 * cfg.gain.multiplier()) as f32)
        }
        else {
            Err(Error::IllegalValue { value, min, max })
        }
    }

    pub fn into_inner(self) -> (I2c, Delay) {
        (self.i2c, self.delay)
    }
}

#[cfg(test)]
#[allow(non_snake_case)]
mod tests {
    use embedded_hal_async::i2c::ErrorKind;
    use embedded_hal_mock::eh1::delay::NoopDelay;
    use embedded_hal_mock::eh1::i2c::Mock as I2c;
    use googletest::prelude::*;
    use rstest::rstest;

    use super::MCP3424;
    use crate::OneShotMode;

    type Testee = MCP3424<I2c, ErrorKind, NoopDelay, OneShotMode>;

    #[rstest]
    #[case([0, 0, 0b00000000, 0], 0.0)]
    #[case([0, 1, 0b00000000, 0], 1.0)] // LSB @ 12 bit
    #[case([255, 255, 0b00000000, 0], -1.0)] // -LSB @ 12 bit
    #[case([0, 1, 0b00000100, 0], 0.25)] // LSB @ 14 bit
    #[case([255, 255, 0b00000100, 0], -0.25)] // LSB @ 14 bit
    #[case([0, 1, 0b00001000, 0], 0.0625)] // LSB @ 16 bit
    #[case([255, 255, 0b00001000, 0], -0.0625)] // LSB @ 16 bit
    #[case([0, 0, 1, 0b00001100], 0.015625)] // LSB @ 18 bit
    #[case([255, 255, 255, 0b00001100], -0.015625)] // LSB @ 18 bit
    #[case([0, 1, 0b00000001, 0], 0.5)] // gain 2x
    #[case([0, 1, 0b00000010, 0], 0.25)] // gain 4x
    #[case([0, 1, 0b00000011, 0], 0.125)] // gain 8x
    fn A_MCP3424_should_convert_an_output_code_into_millivolts(
        #[case] code: [u8; 4],
        #[case] expected: f32
    ) -> Result<()> {

        assert_that!(&Testee::convert(&code), ok(eq(&expected)));

        Ok(())
    }

    #[rstest]
    #[case([8, 0, 0b00000000, 0], -2048)]
    #[case([7, 255, 0b00000000, 0], 2047)]
    #[case([32, 0, 0b00000100, 0], -8192)]
    #[case([31, 255, 0b00000100, 0], 8191)]
    #[case([128, 0, 0b00001000, 0], -32768)]
    #[case([127, 255, 0b00001000, 0], 32767)]
    #[case([2, 0, 0, 0b00001100], -131072)]
    #[case([1, 255, 255, 0b00001100], 131071)]
    fn A_MCP3424_should_return_an_error_if_the_code_represents_an_invalid_value(
        #[case] code: [u8; 4],
        #[case] value: i32,
    ) -> Result<()> {

        assert_that!(Testee::convert(&code), err(matches_pattern!(crate::Error::IllegalValue { value: eq(&value) })));

        Ok(())
    }

    #[rstest]
    fn A_MCP3424_should_return_an_error_if_the_ready_bit_is_set() -> Result<()> {

        let code = [0, 0, 0b10000000, 0];

        assert_that!(Testee::convert(&code), err(anything()));

        Ok(())
    }
}