adc: add support for channels 16 and 17 in ADC1 (#67)

geomatsi · TheZoq2 · commit df8a6e565c69 · 2019-06-11T14:05:40.000+02:00
* adc: add support for channels 16 and 17 in ADC1

Add methods to read from ADC1 special channels:
- channel 16: temperature sensor
- channel 17: internal reference voltage

Note that these methods should be implemented only for ADC1 block
since in ADC2 and ADC3 those channels are connected to Vss.

Signed-off-by: Sergey Matyukevich &lt;geomatsi@gmail.com&gt;

* fixup: sampling time for temperature sensor

Recommended ADC sampling time for temperature sensor is 17.1 usec.
So use approximate sampling time settings to support the
whole range of possible ADC frequencies.

Signed-off-by: Sergey Matyukevich &lt;geomatsi@gmail.com&gt;

* adc: examples

Update existing ADC example according to ADC API changes.
Add new ADC example to read ambient temperature using ADC1 CH16.

Signed-off-by: Sergey Matyukevich &lt;geomatsi@gmail.com&gt;

* fixup: remove redundant interrupt handlers

Signed-off-by: Sergey Matyukevich &lt;geomatsi@gmail.com&gt;

* fixup: remove extra use_hse examples from comments

Signed-off-by: Sergey Matyukevich &lt;geomatsi@gmail.com&gt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -27,6 +27,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Remove all PWM channel configurations except 'all the channels for default remapping' configuratons
 - Update PWM documentation: clarify custom selection of channels
 - Add PWM example for custom selection of channels
+- Add ADC1 reading functions for channels 16 (temperature) and 17 (internal reference voltage)
+- Update existing ADC example according to ADC API changes
+- Add new ADC example to read ambient temperature using ADC1 CH16
 
 ### Changed
 
diff --git a/examples/adc.rs b/examples/adc.rs
@@ -9,7 +9,7 @@ use stm32f1xx_hal::{
     pac,
     adc,
 };
-use cortex_m_rt::{entry,exception,ExceptionFrame};
+use cortex_m_rt::entry;
 
 use cortex_m_semihosting::hprintln;
 
@@ -29,10 +29,10 @@ fn main() -> ! {
     hprintln!("adc freq: {}", clocks.adcclk().0).unwrap();
 
     // Setup ADC
-    let mut adc1 = adc::Adc::adc1(p.ADC1, &mut rcc.apb2);
+    let mut adc1 = adc::Adc::adc1(p.ADC1, &mut rcc.apb2, clocks.adcclk());
 
     #[cfg(feature = "stm32f103")]
-    let mut adc2 = adc::Adc::adc2(p.ADC2, &mut rcc.apb2);
+    let mut adc2 = adc::Adc::adc2(p.ADC2, &mut rcc.apb2, clocks.adcclk());
 
     // Setup GPIOB
     let mut gpiob = p.GPIOB.split(&mut rcc.apb2);
@@ -54,13 +54,3 @@ fn main() -> ! {
         }
     }
 }
-
-#[exception]
-fn HardFault(ef: &ExceptionFrame) -> ! {
-    panic!("{:#?}", ef);
-}
-
-#[exception]
-fn DefaultHandler(irqn: i16) {
-    panic!("Unhandled exception (IRQn = {})", irqn);
-}
diff --git a/examples/adc_temperature.rs b/examples/adc_temperature.rs
@@ -0,0 +1,36 @@
+#![deny(unsafe_code)]
+#![no_main]
+#![no_std]
+
+use panic_semihosting as _;
+
+use stm32f1xx_hal::{
+    prelude::*,
+    pac,
+    adc,
+};
+use cortex_m_rt::entry;
+
+use cortex_m_semihosting::hprintln;
+
+#[entry]
+fn main() -> ! {
+    // Aquire peripherals
+    let p = pac::Peripherals::take().unwrap();
+    let mut flash = p.FLASH.constrain();
+    let mut rcc = p.RCC.constrain();
+
+    let clocks = rcc.cfgr.use_hse(8.mhz()).sysclk(56.mhz()).pclk1(28.mhz()).adcclk(14.mhz()).freeze(&mut flash.acr);
+    hprintln!("sysclk freq: {}", clocks.sysclk().0).unwrap();
+    hprintln!("adc freq: {}", clocks.adcclk().0).unwrap();
+
+    // Setup ADC
+    let mut adc = adc::Adc::adc1(p.ADC1, &mut rcc.apb2, clocks.adcclk());
+
+    // Read temperature sensor
+    loop {
+        let temp = adc.read_temp();
+
+        hprintln!("temp: {}", temp).unwrap();
+    }
+}
diff --git a/src/adc.rs b/src/adc.rs
@@ -5,6 +5,7 @@ use embedded_hal::adc::{Channel, OneShot};
 use crate::gpio::Analog;
 use crate::gpio::{gpioa, gpiob, gpioc};
 use crate::rcc::APB2;
+use crate::time::Hertz;
 
 use crate::stm32::ADC1;
 #[cfg(any(
@@ -17,6 +18,7 @@ pub struct Adc<ADC> {
     rb: ADC,
     sample_time: AdcSampleTime,
     align: AdcAlign,
+    clk: Hertz
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -171,11 +173,12 @@ macro_rules! adc_hal {
                 ///
                 /// Sets all configurable parameters to one-shot defaults,
                 /// performs a boot-time calibration.
-                pub fn $init(adc: $ADC, apb2: &mut APB2) -> Self {
+                pub fn $init(adc: $ADC, apb2: &mut APB2, clk: Hertz) -> Self {
                     let mut s = Self {
                         rb: adc,
                         sample_time: AdcSampleTime::default(),
                         align: AdcAlign::default(),
+                        clk: clk,
                     };
                     s.enable_clock(apb2);
                     s.power_down();
@@ -332,7 +335,14 @@ macro_rules! adc_hal {
                             .rb
                             .smpr1
                             .modify(|_, w| unsafe { w.smp15().bits(self.sample_time.into()) }),
-
+                        16 => self
+                            .rb
+                            .smpr1
+                            .modify(|_, w| unsafe { w.smp16().bits(self.sample_time.into()) }),
+                        17 => self
+                            .rb
+                            .smpr1
+                            .modify(|_, w| unsafe { w.smp17().bits(self.sample_time.into()) }),
                         _ => unreachable!(),
                     }
 
@@ -374,6 +384,85 @@ macro_rules! adc_hal {
     }
 }
 
+impl Adc<ADC1> {
+    fn read_aux(&mut self, chan: u8) -> u16 {
+        let tsv_off = if self.rb.cr2.read().tsvrefe().bit_is_clear() {
+            self.rb.cr2.modify(|_, w| w.tsvrefe().set_bit());
+            true
+        } else {
+            false
+        };
+
+        self.power_up();
+        let val = self.convert(chan);
+        self.power_down();
+
+        if tsv_off {
+            self.rb.cr2.modify(|_, w| w.tsvrefe().clear_bit());
+        }
+
+        val
+    }
+
+    /// Temperature sensor is connected to channel 16 on ADC1. This sensor can be used
+    /// to measure ambient temperature of the device. However note that the returned
+    /// value is not an absolute temperature value.
+    ///
+    /// In particular, according to section 11.10 from Reference Manual RM0008 Rev 20:
+    /// "The temperature sensor output voltage changes linearly with temperature. The offset
+    /// of this line varies from chip to chip due to process variation (up to 45 °C from one
+    /// chip to another). The internal temperature sensor is more suited to applications
+    /// that detect temperature variations instead of absolute temperatures. If accurate
+    /// temperature readings are needed, an external temperature sensor part should be used."
+    ///
+    /// Formula to calculate temperature value is also taken from the section 11.10.
+    pub fn read_temp(&mut self) -> i32 {
+        /// According to section 5.3.18 "Temperature sensor characteristics"
+        /// from STM32F1xx datasheets, TS constants values are as follows:
+        ///   AVG_SLOPE - average slope
+        ///   V_25 - temperature sensor ADC voltage at 25°C
+        const AVG_SLOPE: i32 = 43;
+        const V_25: i32 = 1430;
+
+        let prev_cfg = self.save_cfg();
+
+        // recommended ADC sampling for temperature sensor is 17.1 usec,
+        // so use the following approximate settings
+        // to support all ADC frequencies
+        let sample_time = match self.clk.0 {
+            0 ... 1_200_000 => AdcSampleTime::T_1,
+            1_200_001 ... 1_500_000 => AdcSampleTime::T_7,
+            1_500_001 ... 2_400_000 => AdcSampleTime::T_13,
+            2_400_001 ... 3_100_000 => AdcSampleTime::T_28,
+            3_100_001 ... 4_000_000 => AdcSampleTime::T_41,
+            4_000_001 ... 5_000_000 => AdcSampleTime::T_55,
+            5_000_001 ... 10_000_000 => AdcSampleTime::T_71,
+            _ => AdcSampleTime::T_239,
+        };
+
+        self.set_sample_time(sample_time);
+        let val_temp: i32 = self.read_aux(16u8).into();
+        let val_vref: i32 = self.read_aux(17u8).into();
+        let v_sense = val_temp * 1200 / val_vref;
+
+        self.restore_cfg(prev_cfg);
+
+        (V_25 - v_sense) * 10 / AVG_SLOPE + 25
+    }
+
+    /// Internal reference voltage Vrefint is connected to channel 17 on ADC1.
+    /// According to section 5.3.4 "Embedded reference voltage" from STM32F1xx
+    /// datasheets, typical value of this reference voltage is 1200 mV.
+    ///
+    /// This value is useful when ADC readings need to be converted into voltages.
+    /// For instance, reading from any ADC channel can be converted into voltage (mV)
+    /// using the following formula:
+    ///     v_chan = adc.read(chan) * 1200 / adc.read_vref()
+    pub fn read_vref(&mut self) -> u16 {
+        self.read_aux(17u8)
+    }
+}
+
 #[cfg(any(
     feature = "stm32f100",
     feature = "stm32f101",
