Oneshot ADC

The OneshotAdc allows the user a simple, low-resource way to sporadically (and with moderate frequency needs) measure an analog voltage for multiple channels on a single ADC UNIT. It does not start or manage any tasks and does not perform any filtering on the data. Each time the user calls read_raw(adc_channel_t) or read_mv(adc_channel_t), it block and trigger an analog read for the associated channel (if it was configured to do so).

ADC Example
- How to use example
  - Build and Flash
- Example Output

API Reference

Header File

components/adc/include/oneshot_adc.hpp

Classes

class OneshotAdc : public espp::BaseComponent 

OneshotAdc provides a wrapper around the ESP-IDF oneshot adc subsystem, enabling simple, direct (blocking / slow) measurements of analog values. The read_mv() function will always take a new measurement (therefore it is blocking).

Oneshot ADC Example

    std::vector<espp::AdcConfig> channels{
        {.unit = ADC_UNIT_1, .channel = ADC_CHANNEL_6, .attenuation = ADC_ATTEN_DB_12},
        {.unit = ADC_UNIT_1, .channel = ADC_CHANNEL_7, .attenuation = ADC_ATTEN_DB_12}};
    espp::OneshotAdc adc({
        .unit = ADC_UNIT_1,
        .channels = channels,
    });
    auto task_fn = [&adc, &channels](std::mutex &m, std::condition_variable &cv) {
      static bool use_individual_functions = false;
      if (use_individual_functions) {
        // this iteration, we'll use the read_mv function for each channel
        for (auto &conf : channels) {
          auto maybe_mv = adc.read_mv(conf);
          if (maybe_mv.has_value()) {
            fmt::print("{}: {} mV\n", conf, maybe_mv.value());
          } else {
            fmt::print("{}: no value!\n", conf);
          }
        }
      } else {
        // this iteration, we'll use the read_all_mv function to read all
        // configured channels
        auto voltages = adc.read_all_mv();
        for (const auto &mv : voltages) {
          fmt::print("{} mV\n", mv);
        }
      }
      use_individual_functions = !use_individual_functions;
      // NOTE: sleeping in this way allows the sleep to exit early when the
      // task is being stopped / destroyed
      {
        std::unique_lock<std::mutex> lk(m);
        cv.wait_for(lk, 500ms);
      }
      // don't want to stop the task
      return false;
    };
    auto task = espp::Task({.callback = task_fn,
                            .task_config = {.name = "Oneshot ADC"},
                            .log_level = espp::Logger::Verbosity::INFO});
    task.start();

Public Functions

inline explicit OneshotAdc(const Config &config)

Initialize the oneshot adc reader.

Parameters: config – Config used to initialize the reader.

inline ~OneshotAdc(): Delete and destroy the adc reader.

inline std::vector<int> read_all_mv()

Take a new ADC reading for all configured channels and convert it to voltage (mV) if the unit was properly calibrated. If it was not properly calibrated, then it will return the same value as read_raw().

Returns: std::vector<float> Voltage in mV for all configured channels (if they were configured).

inline std::optional<int> read_raw(const AdcConfig &config)

Take a new ADC reading for the provided config.

Parameters: config – The channel configuration to take a reading from.
Returns: std::optional<float> raw value for the provided channel config (if it was configured).

inline std::optional<int> read_mv(const AdcConfig &config)

Take a new ADC reading for the provided config and convert it to voltage (mV) if the unit was properly calibrated. If it was not properly calibrated, then it will return the same value as read_raw().

Parameters: config – The channel configuration to take a reading from.
Returns: std::optional<float> Voltage in mV for the provided channel config (if it was configured).

inline const std::string &get_name() const