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//! Allows to read the current temperature from the TSIC temperature sensors. //! //! Note that most of this code is ported and heavily modified from C //! to rust using the code found in [arduino-tsic](https://github.com/Schm1tz1/arduino-tsic) //! and other places scattered throughout the internet that used the sensor //! from C. //! //! Please also refer to the [Data Sheet](https://www.ist-ag.com/sites/default/files/DTTSic20x_30x_E.pdf) //! for implementation details. //! //! ## Usage //! //! Please see the comments on both the `with_vdd_control` and `without_vdd_control` constructors for //! their usage and upsides/downsides. //! //! If the library should control both the signal and the vdd pins (recommended): //! //! ```ignore //! use tsic::{SensorType, Tsic}; //! //! let sensor = Tsic::with_vdd_control(SensorType::Tsic306, /* your hal signal input pin */, /* your vdd output pin */); //! //! let mut delay = /* your hal delay */(); //! //! match sensor.read(&mut delay) { //! Ok(t) => defmt::info!("Temp is: {:f32}", t.as_celsius()), //! Err(e) => defmt::warn!("Getting sensor data failed: {:?}", e), //! }; //! ``` //! //! If the library should just control the signal pin: //! //! ```ignore //! use tsic::{SensorType, Tsic}; //! //! let sensor = Tsic::without_vdd_control(SensorType::Tsic306, /* your hal signal input pin */); //! //! let mut delay = /* your hal delay */(); //! //! match sensor.read(&mut delay) { //! Ok(t) => defmt::info!("Temp is: {:f32}", t.as_celsius()), //! Err(e) => defmt::warn!("Getting sensor data failed: {:?}", e), //! }; //! ``` #![cfg_attr(not(test), no_std)] #![forbid(unsafe_code)] #![doc(html_root_url = "https://docs.rs/tsic/0.2.1")] #![warn(missing_docs, rust_2018_idioms, unused_qualifications)] use core::time::Duration; use embedded_hal::blocking::delay::DelayUs; use embedded_hal::digital::v2::{InputPin, OutputPin}; /// The spec defines the sample rate as 128kHz, which is 7.8 microseconds. Since /// we can only sleep for a round number of micros, 8 micros should be close enough. const STROBE_SAMPLING_RATE: Duration = Duration::from_micros(8); /// After power up, an initial power up stabilization delay is needed to /// get reliable measurements. const VDD_POWER_UP_DELAY: Duration = Duration::from_micros(50); /// This is the raw high value at 150°C that according to the docs the sensor /// outputs as a raw value. Everything at this value and be low that is fine, /// the rest is going to be errored. const TSIC_306_RAW_HIGH_TEMP: u16 = 0x7FF; /// The `Tsic` struct is the main entry point when trying to get a temperature reading from a /// TSIC 306 sensor. pub struct Tsic<I: InputPin, O: OutputPin> { /// Right now the sensor type is unused since we only support one, but it provides a forward /// compatible API in case we add support for more in the future. sensor_type: SensorType, signal_pin: I, vdd_pin: Option<O>, } impl<I: InputPin> Tsic<I, DummyOutputPin> { /// Constructs a new `Tsic` without explicit control over the voltage (VDD) pin. /// /// Use this construction method if you either want to manage the power of your /// sensor externally or have it on a permanent voltage connection. Usually in /// this case only the signal pin of the sensor is attached to a GPIO pin of /// your board. /// /// *IMPORTANT*: While this sounds like the simpler method, I recommend using /// the `with_vdd_control` constructor and also attach the VDD pin of the sensor /// to your board. This will reduce the risk of accidentially performing a reading /// during the actual temperature transmission. If you still want to use it this /// way, you probably want to consider retrying on transient failures when executing /// the `read` operation. pub fn without_vdd_control(sensor_type: SensorType, signal_pin: I) -> Self { Self { sensor_type, signal_pin, vdd_pin: None, } } } impl<I: InputPin, O: OutputPin> Tsic<I, O> { /// Constructs a new `Tsic` with explicit control over the voltage (VDD) pin. /// /// Use this method if you want the library to control the voltage (VDD) pin of the /// sensor as well. /// /// This is the recommended approach because it saves power and it makes /// sure that the readings are very consistent (we do not run the risk of trying to /// perform a reading while one is already in-progress, leading to error values). /// /// Usually you need to assign another GPIO pin as an output pin which can drive around /// 3V in high state (see the datasheet for more info), and then the library will control /// the power up, initial delay, reading and power down for you transparently. Of course, /// you can also use the `without_vdd_control` constructor if you want more manual control /// or if you have the sensor on permanent power. pub fn with_vdd_control(sensor_type: SensorType, signal_pin: I, vdd_pin: O) -> Self { Self { sensor_type, signal_pin, vdd_pin: Some(vdd_pin), } } /// Attempts to read from the sensor, might fail (see errors for details if so). /// /// Note that the passed in `Delay` from the HAL needs to be aquired outside of /// this struct and passed in as mutable, because to aquire correct data from the /// sensor the code needs to pause for a certain amount of microseconds. /// /// In case there is an error during the read phase and if the `Tsic` has been constructed /// to manage the VDD pin as well, it will try to shut it down in a best-effort manner as /// well. pub fn read<D: DelayUs<u8>>(&mut self, delay: &mut D) -> Result<Temperature, TsicError> { self.maybe_power_up_sensor(delay)?; let first_packet = match self.read_packet(delay) { Ok(packet) => packet, Err(err) => { self.maybe_power_down_sensor().ok(); return Err(err); } }; let second_packet = match self.read_packet(delay) { Ok(packet) => packet, Err(err) => { self.maybe_power_down_sensor().ok(); return Err(err); } }; self.maybe_power_down_sensor()?; Temperature::new(first_packet, second_packet, &self.sensor_type) } /// Handle VDD pin power up if set during construction. /// /// If we are managing the VDD pin for the user, we need to power up the sensor and then /// apply an initial delay before the reading can continue. fn maybe_power_up_sensor<D: DelayUs<u8>>(&mut self, delay: &mut D) -> Result<(), TsicError> { if let Some(ref mut pin) = self.vdd_pin { pin.set_high().map_err(|_| TsicError::PinWriteError)?; delay.delay_us(VDD_POWER_UP_DELAY.as_micros() as u8); } Ok(()) } /// Handle VDD pin power down if set during construction. /// /// If we are managing the VDD pin for the user, at the end of the measurement we need /// to power it down at the end as well. fn maybe_power_down_sensor(&mut self) -> Result<(), TsicError> { if let Some(ref mut pin) = self.vdd_pin { pin.set_low().map_err(|_| TsicError::PinWriteError)?; } Ok(()) } /// Reads the bits off of the sensor port based on the ZACWire protocol. /// /// From the documentation of the sensor: /// /// When the falling edge of the start bit occurs, measure the time until the /// rising edge of the start bit. This time is the strobe time. /// When the next falling edge occurs, wait for a time period equal to /// the strobe time, and then sample the signal. The data present on the signal /// at this time is the bit being transmitted. Because every bit starts /// with a falling edge, the sampling window is reset with every bit /// transmission. This means errors will not accrue for bits downstream /// from the start bit, as it would with a protocol such as RS232. It is /// recommended, however, that the sampling rate of the signal when acquiring /// the start bit be at least 16x the nominal baud rate. Because the nominal /// baud rate is 8kHz, a 128kHz sampling rate is recommended when acquiring the /// strobe time. /// /// See https://www.ist-ag.com/sites/default/files/ATTSic_E.pdf for /// the full document. fn read_packet<D: DelayUs<u8>>(&self, delay: &mut D) -> Result<Packet, TsicError> { self.wait_until_low()?; let strobe_len = self.strobe_len(delay)?.as_micros() as u8; let mut packet_bits: u16 = 0; for _ in 0..9 { self.wait_until_low()?; delay.delay_us(strobe_len); packet_bits <<= 1; if self.is_high()? { packet_bits |= 1; } self.wait_until_high()?; } Packet::new(packet_bits) } /// Measures the strobe length of the sensor. /// /// According to docs and other code, depending on the temperature the sensor /// can change its strobe length so to be sure we'll just check it before every /// read attempt. /// /// The strobe length should be around 60 microseconds. fn strobe_len<D: DelayUs<u8>>(&self, delay: &mut D) -> Result<Duration, TsicError> { let sampling_rate = STROBE_SAMPLING_RATE.as_micros(); let mut strobe_len = 0; while self.is_low()? { strobe_len += sampling_rate; delay.delay_us(sampling_rate as u8); } Ok(Duration::from_micros(strobe_len as u64)) } /// Checks if the pin is currently in a high state. fn is_high(&self) -> Result<bool, TsicError> { self.signal_pin .is_high() .map_err(|_| TsicError::PinReadError) } /// Checks if the pin is currently in a low state. fn is_low(&self) -> Result<bool, TsicError> { self.signal_pin .is_low() .map_err(|_| TsicError::PinReadError) } /// Returns only once the pin is in a low state. fn wait_until_low(&self) -> Result<(), TsicError> { while self.is_high()? {} Ok(()) } /// Returns only once the pin is in a high state. fn wait_until_high(&self) -> Result<(), TsicError> { while self.is_low()? {} Ok(()) } } /// Contains all errors that can happen during a reading from the sensor. #[derive(Debug)] pub enum TsicError { /// The parity check for one of the packets failed. /// /// This might be a temporary issue, so attempting to perform another /// read might resolve the error. ParityCheckFailed, /// Failed to read the high/low state of signal the pin. PinReadError, /// Failed to set the high/low state of the vdd pin. PinWriteError, /// The temperature reading is out of range. /// /// Note that it includes the raw value (not in celsius!) for /// debugging purposes. TemperatureOutOfRange { /// The (wrong) raw measured temperature. measured: u16, }, } /// Represents a single temperature reading from the TSIC 306 sensor. pub struct Temperature { raw: u16, } impl Temperature { /// Create a full temperature reading from the two individual half reading packets. fn new(first: Packet, second: Packet, sensor_type: &SensorType) -> Result<Self, TsicError> { let raw = (first.value() << 8) | second.value(); if sensor_type.raw_temperature_in_range(raw) { Ok(Self { raw }) } else { Err(TsicError::TemperatureOutOfRange { measured: raw }) } } /// Returns the temperature in degree celsius. pub fn as_celsius(&self) -> f32 { (self.raw as f32 * 200.0 / 2047.0) - 50.0 } } /// A `Packet` represents one half of the full temperature measurement. struct Packet { raw_bits: u16, } impl Packet { /// Creates a new `Packet` from the raw measured bits. /// /// Note that this method performs a parity check on the input data and if /// that fails returns a `TsicError::ParityCheckFailed`. fn new(raw_bits: u16) -> Result<Self, TsicError> { if Self::has_even_parity(raw_bits) { Ok(Self { raw_bits }) } else { Err(TsicError::ParityCheckFailed) } } /// Returns the actual data without the parity bit. fn value(&self) -> u16 { self.raw_bits >> 1 } /// Performs parity bit checking on the raw packet value. fn has_even_parity(raw: u16) -> bool { raw.count_ones() % 2 == 0 } } /// Refers to the sensor type that is used. /// /// Note that it does not matter if you use the SOP-8 or the TO92 style /// sensors as long as the type is correct and the pins are correctly /// assigned. See the data sheet for more information. pub enum SensorType { /// Use this variant if you use the TSic 306 sensor. Tsic306, } impl SensorType { /// Checks if for the given sensor type the raw temperature /// measurement is in the allowed range. fn raw_temperature_in_range(&self, input: u16) -> bool { match self { Self::Tsic306 if input <= TSIC_306_RAW_HIGH_TEMP => true, _ => false, } } } /// This `OutputPin` is used to satisfy the generics when no explicit pin is provided. /// /// Note that you do not want to use this struct, I just couldn' figure out a much /// better way right now, but hopefully it will go away at some point. pub struct DummyOutputPin {} impl OutputPin for DummyOutputPin { type Error = (); fn set_low(&mut self) -> Result<(), Self::Error> { Ok(()) } fn set_high(&mut self) -> Result<(), Self::Error> { Ok(()) } } #[cfg(test)] mod tests { use super::*; #[test] fn test_temp_conversion_for_306() { let sensor_type = SensorType::Tsic306; let input = 0x465u16.to_be_bytes(); // this is 60°c per spec let high_with_parity = ((input[0] as u16) << 1) | 1; let low_with_parity = ((input[1] as u16) << 1) | 0; let packet1 = Packet::new(high_with_parity).unwrap(); let packet2 = Packet::new(low_with_parity).unwrap(); let result = Temperature::new(packet1, packet2, &sensor_type); assert_eq!(60, result.unwrap().as_celsius().round() as u32); } #[test] fn test_error_over_temp_boundary_306() { let sensor_type = SensorType::Tsic306; let input = (TSIC_306_RAW_HIGH_TEMP + 1).to_be_bytes(); let high_with_parity = ((input[0] as u16) << 1) | 1; let low_with_parity = ((input[1] as u16) << 1) | 0; let packet1 = Packet::new(high_with_parity).unwrap(); let packet2 = Packet::new(low_with_parity).unwrap(); let result = Temperature::new(packet1, packet2, &sensor_type); match result { Err(TsicError::TemperatureOutOfRange { measured: 0x800 }) => assert!(true), _ => assert!(false), } } }