CST816 Touch Controller

The Cst816 class provides an interface to the CST816 touch controller.

CST816 Example
- How to use example
- Example Output

API Reference

Header File

components/cst816/include/cst816.hpp

Classes

class Cst816 : public espp::BasePeripheral<std::uint8_t>

Driver for the CST816 touch controller.

For more information, you can look at some reference code and the datasheet here: https://github.com/espressif/esp-bsp/tree/master/components/lcd_touch/esp_lcd_touch_cst816s

Example

    // make the I2C that we'll use to communicate
    espp::I2c i2c({
        .port = I2C_NUM_0,
        .sda_io_num = (gpio_num_t)CONFIG_EXAMPLE_I2C_SDA_GPIO,
        .scl_io_num = (gpio_num_t)CONFIG_EXAMPLE_I2C_SCL_GPIO,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .timeout_ms = 100,
        .clk_speed = 400 * 1000,
    });

    bool has_cst816 = i2c.probe_device(espp::Cst816::DEFAULT_ADDRESS);
    fmt::print("Touchpad probe: {}\n", has_cst816);

    // now make the cst816 which decodes the data
    espp::Cst816 cst816({.write = std::bind(&espp::I2c::write, &i2c, std::placeholders::_1,
                                            std::placeholders::_2, std::placeholders::_3),
                         .read = std::bind(&espp::I2c::read, &i2c, std::placeholders::_1,
                                           std::placeholders::_2, std::placeholders::_3),
                         .log_level = espp::Logger::Verbosity::WARN});

    // and finally, make the task to periodically poll the cst816 and print
    // the state
    auto task_fn = [&cst816](std::mutex &m, std::condition_variable &cv) {
      std::error_code ec;
      // update the state
      bool new_data = cst816.update(ec);
      if (ec) {
        fmt::print("Could not update state\n");
        return false;
      }
      if (!new_data) {
        return false; // don't stop the task
      }
      // get the state
      bool home_pressed = false;
      home_pressed = cst816.get_home_button_state();
      fmt::print("home_pressed: {}\n", home_pressed);
      uint8_t num_touch_points = 0;
      uint16_t x = 0, y = 0;
      cst816.get_touch_point(&num_touch_points, &x, &y);
      if (ec) {
        fmt::print("Could not get touch point\n");
        return false;
      }
      fmt::print("num_touch_points: {}, x: {}, y: {}\n", num_touch_points, x, y);
      // 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, 50ms);
      }
      return false; // don't stop the task
    };
    auto task = espp::Task({.callback = task_fn,
                            .task_config = {.name = "Cst816 Task"},
                            .log_level = espp::Logger::Verbosity::WARN});
    task.start();

Note

This chip does not respond to I2C commands normally, only after an event. To properly interact with this chip, you should register an interrupt on the chip’s IRQ line. After the IRQ line is asserted, it will respond to I2C reads for a short period of time.

Public Types

typedef std::function<bool(uint8_t)> probe_fn

Function to probe the peripheral

Param address: The address to probe
Return: True if the peripheral is found at the given address

Public Functions

inline explicit Cst816(const Config &config)

Constructor for the CST816 driver.

Parameters: config – The configuration for the driver

inline bool update(std::error_code &ec)

Update the state of the CST816 driver.

Parameters: ec – Error code to set if an error occurs
Returns: True if the CST816 has new data, false otherwise

inline uint8_t get_num_touch_points() const

Get the number of touch points.

Note

This is a cached value from the last update() call

Returns: The number of touch points as of the last update

inline void get_touch_point(uint8_t *num_touch_points, uint16_t *x, uint16_t *y) const

Get the touch point data.

Note

This is a cached value from the last update() call

Parameters

num_touch_points – The number of touch points as of the last update
x – The x coordinate of the touch point
y – The y coordinate of the touch point

inline bool get_home_button_state() const

Get the home button state.

Note

This is a cached value from the last update() call

Returns: True if the home button is pressed, false otherwise

inline bool probe (std::error_code &ec) requires(true)

Probe the peripheral

Note

This function is thread safe

Note

If the probe function is not set, this function will return false and set the error code to operation_not_supported

Note

This function is only available if UseAddress is true

Parameters: ec – The error code to set if there is an error
Returns: True if the peripheral is found

inline void set_address (uint8_t address) requires(true)

Set the address of the peripheral

Note

This function is thread safe

Note

This function is only available if UseAddress is true

Parameters: address – The address of the peripheral

inline void set_probe (const probe_fn &probe) requires(true)

Set the probe function

Note

This function is thread safe

Note

This should rarely be used, as the probe function is usually set in the constructor. If you need to change the probe function, consider using the set_config function instead.

Note

This function is only available if UseAddress is true

Parameters: probe – The probe function

inline void set_write(const write_fn &write)

Set the write function

Note

This function is thread safe

Note

This should rarely be used, as the write function is usually set in the constructor. If you need to change the write function, consider using the set_config function instead.

Parameters: write – The write function

inline void set_read(const read_fn &read)

Set the read function

Note

This function is thread safe

Note

This should rarely be used, as the read function is usually set in the constructor. If you need to change the read function, consider using the set_config function instead.

Parameters: read – The read function

inline void set_read_register(const read_register_fn &read_register)

Set the read register function

Note

This function is thread safe

Note

This should rarely be used, as the read register function is usually set in the constructor. If you need to change the read register function, consider using the set_config function instead.

Parameters: read_register – The read register function

inline void set_write_then_read(const write_then_read_fn &write_then_read)

Set the write then read function

Note

This function is thread safe

Note

This should rarely be used, as the write then read function is usually set in the constructor. If you need to change the write then

Parameters: write_then_read – The write then read function

inline void set_separate_write_then_read_delay(const std::chrono::milliseconds &delay)

Set the delay between the write and read operations in write_then_read

Note

This function is thread safe

Note

This should rarely be used, as the delay is usually set in the constructor. If you need to change the delay, consider using the set_config function instead.

Note

This delay is only used if the write_then_read function is not set to a custom function and the write and read functions are separate functions.

Parameters: delay – The delay between the write and read operations in write_then_read

inline void set_config(const Config &config)

Set the configuration for the peripheral

Note

This function is thread safe

Note

The configuration should normally be set in the constructor, but this function can be used to change the configuration after the peripheral has been created - for instance if the peripheral could be found on different communications buses.

Parameters: config – The configuration for the peripheral

inline void set_config(Config &&config)

Set the configuration for the peripheral

Note

This function is thread safe

Note

The configuration should normally be set in the constructor, but this function can be used to change the configuration after the peripheral has been created - for instance if the peripheral could be found on different communications buses.

Parameters: config – The configuration for the peripheral

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

Get the name of the component

Note

This is the tag of the logger

Returns: A const reference to the name of the component

inline void set_log_tag(const std::string_view &tag)

Set the tag for the logger

Parameters: tag – The tag to use for the logger

inline espp::Logger::Verbosity get_log_level() const

Get the log level for the logger

See also

Logger::Verbosity

See also

Logger::set_verbosity

Returns: The verbosity level of the logger

inline void set_log_level(espp::Logger::Verbosity level)

Set the log level for the logger

See also

Logger::Verbosity

See also

Logger::set_verbosity

Parameters: level – The verbosity level to use for the logger

inline void set_log_verbosity(espp::Logger::Verbosity level)

Set the log verbosity for the logger

See also

set_log_level

See also

Logger::Verbosity

See also

Logger::set_verbosity

Note

This is a convenience method that calls set_log_level

Parameters: level – The verbosity level to use for the logger

inline espp::Logger::Verbosity get_log_verbosity() const

Get the log verbosity for the logger

See also

get_log_level

See also

Logger::Verbosity

See also

Logger::get_verbosity

Note

This is a convenience method that calls get_log_level

Returns: The verbosity level of the logger

inline void set_log_rate_limit(std::chrono::duration<float> rate_limit)

Set the rate limit for the logger

See also

Logger::set_rate_limit

Note

Only calls to the logger that have _rate_limit suffix will be rate limited

Parameters: rate_limit – The rate limit to use for the logger

Public Static Attributes

static constexpr uint8_t DEFAULT_ADDRESS = 0x15: Default address for the CST816 chip.

struct Config

Configuration for the CST816 driver.

Public Members

BasePeripheral::write_fn write: Function for writing to the CST816 chip.

BasePeripheral::read_fn read: Function for reading from the CST816 chip.

uint8_t address = DEFAULT_ADDRESS : Which address to use for this chip?

espp::Logger::Verbosity log_level = {espp::Logger::Verbosity::WARN}: Log verbosity for the input driver.