max3010x 0.2.0

Platform-agnostic Rust driver for the MAX3010x high-sensitivity pulse oximeter and heart-rate sensor for wearable health.
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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240

//! Reading data method implementation.

use super::{
    marker, private, BitFlags, Error, InterruptStatus, LedPulseWidth, Max3010x, Register,
    SamplingRate, DEVICE_ADDRESS,
};
use hal::i2c;

#[doc(hidden)]
pub trait ChannelCount<IC, MODE>: private::Sealed {
    const CHANNEL_COUNT: u8;
}

impl ChannelCount<marker::ic::Max30102, marker::mode::HeartRate> for marker::mode::HeartRate {
    const CHANNEL_COUNT: u8 = 1;
}

impl ChannelCount<marker::ic::Max30102, marker::mode::Oximeter> for marker::mode::Oximeter {
    const CHANNEL_COUNT: u8 = 2;
}

impl ChannelCount<marker::ic::Max30102, marker::mode::MultiLed> for marker::mode::MultiLed {
    const CHANNEL_COUNT: u8 = 2;
}

impl<I2C, E, IC, MODE> Max3010x<I2C, IC, MODE>
where
    I2C: i2c::I2c<Error = E>,
    MODE: ChannelCount<IC, MODE>,
{
    /// Reads samples from FIFO.
    ///
    /// Reads data from the FIFO until all the available samples are read or
    /// the input buffer is full.
    ///
    /// Returns the number of _samples_ read.
    ///
    /// The output buffer must contain one element per channel per sample.
    ///
    /// Note: This method takes care of shifting the data according to the
    /// ADC resolution.
    pub fn read_fifo(&mut self, output_data: &mut [u32]) -> Result<u8, Error<E>> {
        let mode_channels = usize::from(MODE::CHANNEL_COUNT);

        if output_data.len() < mode_channels {
            return Ok(0);
        }
        let samples = self.get_available_sample_count()?;
        let samples_fitting_in_input = output_data.len() / mode_channels;
        let sample_count = core::cmp::min(usize::from(samples), samples_fitting_in_input);
        if sample_count != 0 {
            self.read_samples(sample_count, output_data)?;
        }
        Ok(sample_count as u8) // the maximum is 32 so this is ok
    }

    fn read_samples(&mut self, sample_count: usize, output: &mut [u32]) -> Result<(), Error<E>> {
        const BYTES_PER_SAMPLE: usize = 3;
        const MAX_CHANNEL_COUNT: usize = 2; // for max30102
        const FIFO_SAMPLE_SIZE: usize = 32;

        let mode_channels = usize::from(MODE::CHANNEL_COUNT);
        let sample_shift = self.get_sample_shift();
        let byte_count = sample_count * mode_channels * BYTES_PER_SAMPLE;
        // maximum size (could be optimized by using mode_channels but this
        // needs https://github.com/rust-lang/rust/issues/42863)
        let mut data = [0; FIFO_SAMPLE_SIZE * MAX_CHANNEL_COUNT * BYTES_PER_SAMPLE];
        self.read_data(Register::FIFO_DATA, &mut data[..byte_count])?;
        for (out_idx, out_item) in output
            .iter_mut()
            .enumerate()
            .take(sample_count * mode_channels)
        {
            let sample_idx = out_idx * BYTES_PER_SAMPLE;
            *out_item = (u32::from(data[sample_idx]) << 16
                | u32::from(data[sample_idx + 1]) << 8
                | u32::from(data[sample_idx + 2]))
                >> sample_shift;
        }
        Ok(())
    }

    fn get_sample_shift(&self) -> usize {
        match self.get_pulse_width() {
            LedPulseWidth::Pw69 => 3,
            LedPulseWidth::Pw118 => 2,
            LedPulseWidth::Pw215 => 1,
            LedPulseWidth::Pw411 => 0,
        }
    }
}

impl<I2C, IC, MODE> Max3010x<I2C, IC, MODE> {
    pub(crate) fn get_pulse_width(&self) -> LedPulseWidth {
        let pw_bits = self.spo2_config.bits & (BitFlags::LED_PW0 | BitFlags::LED_PW1);
        match pw_bits {
            0 => LedPulseWidth::Pw69,
            1 => LedPulseWidth::Pw118,
            2 => LedPulseWidth::Pw215,
            3 => LedPulseWidth::Pw411,
            _ => unreachable!(),
        }
    }

    pub(crate) fn get_sampling_rate(&self) -> SamplingRate {
        convert_sampling_rate(self.spo2_config.bits)
    }
}

fn convert_sampling_rate(spo2_config: u8) -> SamplingRate {
    let sr_bits =
        (spo2_config & (BitFlags::SPO2_SR0 | BitFlags::SPO2_SR1 | BitFlags::SPO2_SR2)) >> 2;
    match sr_bits {
        0 => SamplingRate::Sps50,
        1 => SamplingRate::Sps100,
        2 => SamplingRate::Sps200,
        3 => SamplingRate::Sps400,
        4 => SamplingRate::Sps800,
        5 => SamplingRate::Sps1000,
        6 => SamplingRate::Sps1600,
        7 => SamplingRate::Sps3200,
        _ => unreachable!(),
    }
}

impl<I2C, E, IC, MODE> Max3010x<I2C, IC, MODE>
where
    I2C: i2c::I2c<Error = E>,
{
    /// Get number of samples available for reading from FIFO.
    pub fn get_available_sample_count(&mut self) -> Result<u8, Error<E>> {
        let mut data = [0; 3];
        self.read_data(Register::FIFO_WR_PTR, &mut data)?;
        let wr_ptr = data[0] & 0x1F;
        let rd_ptr = data[2] & 0x1F;
        let has_rolled_over = rd_ptr > wr_ptr;
        if has_rolled_over {
            Ok(32 - rd_ptr + wr_ptr)
        } else {
            Ok(wr_ptr - rd_ptr)
        }
    }

    /// Get number of samples lost from FIFO.
    ///
    /// If FIFO rollover is not enabled, when the FIFO is full the samples are
    /// not pushed on to the FIFO.
    pub fn get_overflow_sample_count(&mut self) -> Result<u8, Error<E>> {
        let v = self.read_register(Register::OVF_COUNTER)?;
        Ok(v & 0x1F)
    }

    /// Perform a temperature measurement.
    ///
    /// This starts a temperature measurement if none is currently ongoing.
    /// When the measurement is finished, returns the result.
    pub fn read_temperature(&mut self) -> nb::Result<f32, Error<E>> {
        let config = self
            .read_register(Register::TEMP_CONFIG)
            .map_err(nb::Error::Other)?;
        if config & BitFlags::TEMP_EN != 0 {
            return Err(nb::Error::WouldBlock);
        }
        if self.temperature_measurement_started {
            let mut data = [0, 0];
            self.read_data(Register::TEMP_INT, &mut data)
                .map_err(nb::Error::Other)?;
            let temp_int = data[0] as i8;
            let temp_frac = f32::from(data[1]) * 0.0625;
            let temp = f32::from(temp_int) + temp_frac;
            self.temperature_measurement_started = false;
            Ok(temp)
        } else {
            self.write_data(&[Register::TEMP_CONFIG, BitFlags::TEMP_EN])
                .map_err(nb::Error::Other)?;
            self.temperature_measurement_started = true;
            Err(nb::Error::WouldBlock)
        }
    }

    /// Read status of all interrupts
    pub fn read_interrupt_status(&mut self) -> Result<InterruptStatus, Error<E>> {
        let mut data = [0; 2];
        self.read_data(Register::INT_STATUS, &mut data)?;
        let status = InterruptStatus {
            power_ready: (data[0] & BitFlags::PWR_RDY_INT) != 0,
            fifo_almost_full: (data[0] & BitFlags::FIFO_A_FULL_INT) != 0,
            new_fifo_data_ready: (data[0] & BitFlags::PPG_RDY_INT) != 0,
            alc_overflow: (data[0] & BitFlags::ALC_OVF_INT) != 0,
            temperature_ready: (data[1] & BitFlags::DIE_TEMP_RDY_INT) != 0,
        };
        Ok(status)
    }

    /// Get revision ID
    pub fn get_revision_id(&mut self) -> Result<u8, Error<E>> {
        self.read_register(Register::REV_ID)
    }

    /// Get part ID
    pub fn get_part_id(&mut self) -> Result<u8, Error<E>> {
        self.read_register(Register::PART_ID)
    }

    fn read_register(&mut self, register: u8) -> Result<u8, Error<E>> {
        let mut data = [0];
        self.read_data(register, &mut data)?;
        Ok(data[0])
    }

    fn read_data(&mut self, register: u8, data: &mut [u8]) -> Result<(), Error<E>> {
        self.i2c
            .write_read(DEVICE_ADDRESS, &[register], data)
            .map_err(Error::I2C)
    }
}

#[cfg(test)]
mod convert_sampling_rate_tests {
    use super::{convert_sampling_rate, SamplingRate};
    macro_rules! convert_sampling_rate_test {
        ($name:ident, $bits:expr, $rate:ident) => {
            #[test]
            fn $name() {
                let rate = convert_sampling_rate($bits);
                assert_eq!(SamplingRate::$rate, rate);
            }
        };
    }

    convert_sampling_rate_test!(sps50, 0 << 2, Sps50);
    convert_sampling_rate_test!(sps100, 1 << 2, Sps100);
    convert_sampling_rate_test!(sps200, 2 << 2, Sps200);
    convert_sampling_rate_test!(sps400, 3 << 2, Sps400);
    convert_sampling_rate_test!(sps800, 4 << 2, Sps800);
    convert_sampling_rate_test!(sps1000, 5 << 2, Sps1000);
    convert_sampling_rate_test!(sps1600, 6 << 2, Sps1600);
    convert_sampling_rate_test!(sps3200, 7 << 2, Sps3200);
    convert_sampling_rate_test!(other_bits_are_ignored, 0b1110_0011, Sps50);
}