update lookup table example

Chapter11/compile_time/hal/adc/inc/adc.hpp

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+#pragma once
+
+#include <expected>
+
+#include <units.hpp>
+
+namespace hal
+{
+    class adc {
+    public:
+        enum class error {
+            timeout
+        };
+
+        virtual void init() = 0;
+        virtual std::expected<units::voltage, adc::error> get_reading() = 0;
+    };
+};

Chapter11/compile_time/hal/adc/inc/adc_stm32.hpp

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+#pragma once
+
+#include <adc.hpp>
+#include <units.hpp>
+
+#include <stm32f0xx_hal.h>
+#include <stm32f072xb.h>
+
+namespace hal 
+{
+
+    class adc_stm32 : public adc{
+    public:
+        adc_stm32(units::voltage ref_voltage) : ref_voltage_(ref_voltage) {}
+
+        void init() override;
+        std::expected<units::voltage, adc::error> get_reading() override;
+    private:
+        ADC_HandleTypeDef adc_handle_;
+        units::voltage ref_voltage_;
+    };
+};

Chapter11/compile_time/hal/adc/src/adc_stm32.cpp

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+#include <adc_stm32.hpp>
+
+void hal::adc_stm32::init() {
+    ADC_ChannelConfTypeDef sConfig = {0};
+
+    /** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
+    */
+    adc_handle_.Instance = ADC1;
+    adc_handle_.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
+    adc_handle_.Init.Resolution = ADC_RESOLUTION_12B;
+    adc_handle_.Init.DataAlign = ADC_DATAALIGN_RIGHT;
+    adc_handle_.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;
+    adc_handle_.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
+    adc_handle_.Init.LowPowerAutoWait = DISABLE;
+    adc_handle_.Init.LowPowerAutoPowerOff = DISABLE;
+    adc_handle_.Init.ContinuousConvMode = DISABLE;
+    adc_handle_.Init.DiscontinuousConvMode = DISABLE;
+    adc_handle_.Init.ExternalTrigConv = ADC_SOFTWARE_START;
+    adc_handle_.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
+    adc_handle_.Init.DMAContinuousRequests = DISABLE;
+    adc_handle_.Init.Overrun = ADC_OVR_DATA_PRESERVED;
+    if (HAL_ADC_Init(&adc_handle_) != HAL_OK)
+    {
+        //Error_Handler();
+    }
+
+    /** Configure for the selected ADC regular channel to be converted.
+    */
+    sConfig.Channel = ADC_CHANNEL_0;
+    sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;
+    sConfig.SamplingTime = ADC_SAMPLETIME_1CYCLE_5;
+    if (HAL_ADC_ConfigChannel(&adc_handle_, &sConfig) != HAL_OK)
+    {
+        //Error_Handler();
+    }
+}
+        
+std::expected<units::voltage, hal::adc::error> hal::adc_stm32::get_reading() {
+    HAL_ADC_Start(&adc_handle_);
+    if(HAL_ADC_PollForConversion(&adc_handle_, 1000) != HAL_OK) {
+        return std::unexpected(hal::adc::error::timeout);
+    }
+
+    auto adc_val = HAL_ADC_GetValue(&adc_handle_);
+
+    return ref_voltage_ * adc_val / 4096.f;
+}