Struct Scratchpad 

pub struct Scratchpad { /* private fields */ }

A decoded, CRC-verified DS18B20 scratchpad.

The scratchpad is nine bytes: temperature LSB and MSB, the high and low alarm thresholds, the configuration byte, three reserved bytes, and a CRC. parse checks the CRC before exposing any of it.

Examples

use pamoja_sensors::ds18b20::{temperature_from_celsius, Resolution, Scratchpad};

// What a part sitting at +25.0625 °C, set to 12-bit steps with its thresholds at
// +75/-10 °C, puts on the bus. A driver reads these nine bytes off the wire.
let bytes = Scratchpad::new(
    temperature_from_celsius(25.0625, Resolution::Bits12),
    Resolution::Bits12,
    75,
    -10,
)
.to_bytes();

let scratchpad = Scratchpad::parse(&bytes)?;
assert_eq!(scratchpad.temperature_micro_celsius(), 25_062_500);
assert_eq!(scratchpad.resolution(), Resolution::Bits12);

Implementations

impl Scratchpad

pub fn parse(bytes: &[u8; 9]) -> Result<Scratchpad, SensorError>

Parses and CRC-checks a nine-byte scratchpad.

Arguments

• bytes - the nine scratchpad bytes in the order the device sends them, the ninth being the CRC.

Returns

The decoded scratchpad.

Errors

Returns SensorError::Crc if the CRC byte does not match the first eight, which means the read was corrupted and should be repeated.

pub fn new( raw_temperature: i16, resolution: Resolution, alarm_high: i8, alarm_low: i8, ) -> Scratchpad

Builds the scratchpad a part in the given state reports.

This is the inverse of parse, so a node can be developed and tested against the bytes a thermometer would send without one attached.

Arguments

• raw_temperature - the 16-bit two’s-complement temperature register, as a signed value; temperature_from_celsius builds one from a temperature.
• resolution - the resolution the part is configured for.
• alarm_high - the high alarm threshold in whole degrees Celsius (TH).
• alarm_low - the low alarm threshold in whole degrees Celsius (TL).

Returns

The scratchpad holding those values.

pub fn to_bytes(&self) -> [u8; 9]

Returns the nine bytes a part holding this scratchpad puts on the bus.

Bytes 5 to 7 are the reserved bytes, which a part reports but which carry no reading; they are filled with the values its scratchpad figure shows so the frame is the one a device would actually send. The ninth byte is the CRC over the other eight, so the result parses.

Returns

The nine scratchpad bytes in transmission order, CRC last.

pub fn raw_temperature(&self) -> i16

Returns the raw temperature register value.

Returns

The 16-bit two’s-complement register, as a signed value.

pub fn temperature_micro_celsius(&self) -> i32

Returns the temperature in micro-degrees Celsius.

Returns

The temperature, exact, in millionths of a degree Celsius.

pub fn temperature_celsius(&self) -> f32

Returns the temperature in degrees Celsius.

Returns

The temperature in degrees Celsius.

pub fn resolution(&self) -> Resolution

Returns the configured conversion resolution.

pub fn alarm_high(&self) -> i8

Returns the high temperature alarm threshold (TH), in whole degrees Celsius.

pub fn alarm_low(&self) -> i8

Returns the low temperature alarm threshold (TL), in whole degrees Celsius.

Trait Implementations

impl Clone for Scratchpad

fn clone(&self) -> Scratchpad

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Scratchpad

impl Debug for Scratchpad

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Scratchpad

impl PartialEq for Scratchpad

fn eq(&self, other: &Scratchpad) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Scratchpad