Crate akafugu_twidisplay[−][src]
Expand description
A platform agnostic Rust driver for the Akafugu TWIDisplay 4-digit 7-segment display controller,
based on the embedded-hal traits.
This driver allows you to:
- Display single digits or characters, also at a selected position
- Display text, although some characters may not be available (see display documentation)
- Clear the display
- Show the current I2C address
- Change the I2C address (experimental function)
- Display time in HH.MM format
- Display temperature or humidity, with settable lower/upper threshold
The device
The TWI 7-segment Display is an easy to use 4-digit 7-segment display that is controlled using the TWI (I2C compatible) protocol. It is based on an ATMega4313 MCU, acting as a peripheral I2C device.
Information: TWIDisplay
Usage examples (see also examples folder)
Please find additional examples using hardware in this repository: examples
Initialization
A new instance of the device is created as follows:
use akafugu_twidisplay::*:
let mut akafugu = TWIDisplay::new(i2c, DEFAULT_ADDRESS);The default address is 0x12. If the address was changed with the set_address() function,
the new address must be used after a power down-power up sequence.
Main functions
Display can be cleared with the following command:
akafugu.clear_display().unwrap();Digits and/or characters can either be simply sent to display, or displayed at defined positions.
// display digit '7' at position 2 (positions are 0,1,2,3 from left to right)
akafugu.display_digit(2, 7).unwrap();
// display character 'P' at position 3
akafugu.display_char(3,'P').unwrap();If a digit/character is just sent to the display, it will appear according to the selected mode (scroll or rotate) - please see the documentation.
akafugu.send_char('A').unwrap();
akafugu.send_char('B').unwrap();
akafugu.send_char('C').unwrap();
akafugu.send_char('D').unwrap();This will display ABCD.
akafugu.send_char('E').unwrap();Depending on the selected mode the display will show now:
- in SCROLL mode: ‘BCDE’
- in ROTATE mode: ‘EBCD’
Text can be sent to display as string literals:
akafugu.send_text("HELLO LOOP PULL CALL").unwrap();Numbers from 0-9999 range can be displayed with the following function:
akafugu.display_number(1234).unwrap();NOTE: Numbers will be displayed with leading zeroes, e.g. 0023.
Dots can be turned on or off using this function:
// this will turn on the first and the third dot from the left
akafugu.display_dots([true, false, true, false]).unwrap();Control functions
Display mode can be changed as follows:
akafugu.set_mode(Mode::Scroll).unwrap(); // default mode is `Rotate`Brightness can be set between 0 and 255, where 127 is approx. 50% brightness.
akafugu.set_brightness(200).unwrap();The I2C address of the device can be changed from the default 0x12 as follows:
akafugu.set_address(0x20).unwrap();The new address will be active after a power down, power up sequence.
NOTE: According to the documentation, the allowed range of addresses is 0x00-0x7F, but addresses including and over 0x40 don’t seem to work correctly, even though they are correctly displayed. In such case 0x00 must be used to access the device and change the address again. For this reason in this driver the address setting is restricted to 0x00-0x39 range.
To show the current I2C address use the following command:
akafugu.display_address().unwrap();The same can be achieved by simply connecting only the VCC and GND pins of the display.
Convenience functions
The driver has three additional functions, that can be useful for clock or sensor applications.
Display time
Time is displayed in HH.MM format, with the central dot displayed or not:
// get time from the clock
let (hours, minutes, seconds) = some_rtc_function();
// blink the dot: on if number of seconds is even, otherwise off
if seconds % 2 == 0 {
akafugu.display_time(hours, minutes, true).unwrap()
} else {
akafugu.display_time(hours, minutes, false).unwrap()
}Display temperature
Displays integer temperature values with a unit of choice (Celsius/Fahrenheit), no leading zeros.
The function allows setting lower and upper threshold: if the supplied value is below the lower threshold,
the display will show -LL-, if above the upper threshold, it will show -HH-.
This can be useful for sensor applications such as weather stations: thresholds can be set to the limits of
reliable readings, e.g. -30 and +60 Celsius degrees, etc.
Thresholds are optional and if not given, will default to the minimum and maximum limits, which are set to -99 and 999, respectively.
If the supplied value exceeds the limit, the display will show ----.
let temp_reading = some_sensor_reading();
// display temperature with unit 'C', lower threshold at -50 degrees,
// no upper threshold (defaults to +999)
// temp_reading < -50 will show as `-LL-`, temp_reading < -99 will show as `----`
akafugu.display_temperature(temperature, TempUnits::Celsius, Some(-50), None).unwrap();Display humidity
Displays integer humidity values with a default unit ‘H’, no leading zeros.
The function allows setting lower and upper threshold: if the supplied value is below the lower threshold,
the display will show -LL-, if above the upper threshold, it will show -HH-.
This can be useful for sensor applications such as weather stations: thresholds can be set to the limits of
reliable readings, e.g. between 10 and 90% of relative humidity.
Thresholds are optional and if not given, will default to the minimum and maximum limits, which are set to 0 and 100, respectively.
If the supplied value exceeds the limit, the display will show ----.
let hum_reading = some_sensor_reading();
// display humidity, lower threshold at 10%, upper threshold at 90%.
// temp_reading < 10 will show as `-LL-`, temp_reading > 90 will show as `-HH-`,
// readings below 0 or above 100 will show as `----`
akafugu.display_humidity(humidity, Some(10), Some(90)).unwrap();Structs
TWIDisplay driver, that holds the I2C bus instance and the I2C address used
Enums
All possible errors in this crate
Two possible display modes
Possible choices for temperature units
Constants
Default I2C address for the device