LilyGo T-Keyboard

The TKeyboard component provides a simple interface to the T-Keyboard keypad. It allows you to read which key is currently pressed.

LilyGo T-Keyboard Example
- How to use example
  - Hardware Required
  - Build and Flash
- Example Output

API Reference

Header File

components/t_keyboard/include/t_keyboard.hpp

Classes

class TKeyboard : public espp::BasePeripheral<>

Class for interacting with the LilyGo T-Keyboard.

This class is used to interact with the LilyGo T-Keyboard. It is designed as a peripheral component for use with a serial interface such as I2C. On The T-Keyboard, you can press Alt+B to toggle the keyboard backlight.

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,
    });
    // now make the tkeyboard which decodes the data
    espp::TKeyboard tkeyboard(
        {.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),
         .key_cb = [](uint8_t key) { fmt::print("'{}' Pressed!\n", (char)key); },
         .auto_start = false, // can't auto start since we need to provide power
         .log_level = espp::Logger::Verbosity::WARN});

    // on the LilyGo T-Deck, the peripheral power control pin must be set high
    // to enable peripheral power
    auto power_ctrl = GPIO_NUM_10;
    gpio_set_direction(power_ctrl, GPIO_MODE_OUTPUT);
    gpio_set_level(power_ctrl, 1);

    do {
      fmt::print("Waiting for tkeyboard to boot up...\n");
      std::this_thread::sleep_for(250ms);
    } while (!i2c.probe_device(espp::TKeyboard::DEFAULT_ADDRESS));

    fmt::print("Tkeyboard ready!\n");
    tkeyboard.start();

Public Types

typedef std::function<void(uint8_t)> key_cb_fn

The function signature for the key callback function.

This function is called when a key is pressed.

Param key: The key that was pressed.

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 TKeyboard(const Config &config)

Constructor for the TKeyboard class.

Parameters: config – The configuration to use.

inline uint8_t get_key() const

Get the currently pressed key.

This function returns the currently pressed key.

Note

This function will return 0 if no key has been pressed.

Returns: The currently pressed key.

inline uint8_t read_key(std::error_code &ec)

Read a key from the keyboard.

This function reads a key from the keyboard. It will return 0 and set the error code if an error occurs. If the keyboard task is running, it will return 0 and set the error code. If the keyboard task is not running, it will return the key that was read, and update the currently pressed key.

See also

get_key()

Note

This function will return 0 if no key was read.

Note

This function will return 0 if an error occurs.

Note

This function will set the error code if the keyboard task is running.

Parameters: ec – The error code to set if an error occurs.
Returns: The key that was read.

inline bool start()

Start the keyboard task.

This function starts the keyboard task. It should be called after the keyboard has been initialized.

Returns: True if the task was started, false otherwise.

inline bool stop()

Stop the keyboard task.

This function stops the keyboard task.

Returns: True if the task was stopped, false otherwise.

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

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(UseAddress)

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(UseAddress)

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 = 0x55: The default address of the keyboard.

struct Config

The configuration structure for the keyboard.

Public Members

BasePeripheral::write_fn write: The write function to use.

BasePeripheral::read_fn read: The read function to use.

key_cb_fn key_cb: The key callback function to use. This function will be called when a key is pressed if it is not null and the keyboard task is running.

uint8_t address = DEFAULT_ADDRESS : The address of the keyboard.

std::chrono::milliseconds polling_interval = std::chrono::milliseconds(10): The polling interval for the keyboard.

bool auto_start = true: Whether or not to automatically start the keyboard task.

Logger::Verbosity log_level = Logger::Verbosity::WARN : The log level to use.