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65 lines
2.3 KiB
Markdown
65 lines
2.3 KiB
Markdown
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# STM32F411CEU6 encoder polling and LCD display
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This example uses an STM32F411CEU6 microcontroller on the Blackpill board to interface with an I2C LCD display and a rotary encoder.
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## Features
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- **Rotary Encoder Integration**: Reads input from a rotary encoder to adjust a value.
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- **I2C LCD Display**: Displays the current encoder value on an I2C-connected HD44780 LCD.
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## Working principle
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The hardware task `tim2_timeout_interrupt_handler` polls the encoder state on each interrupt generated by TIM2, and updates the displayed value accordingly.
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## Code Overview
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### Key Components
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- **Knob Struct**: Placeholder for the rotary encoder and its current value.
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- **LCD I2C Communication**: Uses I2C protocol to communicate with the HD44780 LCD.
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- **Timers**: Utilizes TIM1 for delays and TIM2 for polling the rotary encoder.
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### Important Constants
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- `LCD_I2C_ADDRESS`: The I2C address of the LCD display.
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### Initialization
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- **System Clock**: Configured to use an external 25 MHz clock.
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- **GPIO Setup**: Configures GPIO pins for the LED, rotary encoder, and I2C communication.
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- **I2C Initialization**: Sets up the I2C bus for LCD communication.
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- **LCD Initialization**: Initializes the LCD and displays initial messages.
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- **Timer Setup**: Configures TIM2 at 2 kHz and generate interrupts.
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### Tasks and Handlers
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- **idle**: Background task that runs when no other tasks are active.
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- **tim2_timeout_interrupt_handler**: Handles interrupts generated by TIM2, updates the rotary encoder value, and displays the value on the LCD.
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### Utility Functions
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- `u8_to_str(n: u8) -> [u8; 3]`: Converts an 8-bit integer to a 3-character string representation.
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## Dependencies
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- **hd44780-driver**: Driver for HD44780 LCD over I2C.
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- **rotary_encoder_embedded**: Library for handling rotary encoders.
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- **defmt**: Logging framework for embedded systems.
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## How-to
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### Build
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Run `cargo build --release` to compile the code. If you run it for the first time, it will take some time to download and compile dependencies.
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### Run
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Install `probe-rs` and configure it using the [debugging extension for VScode](https://probe.rs/docs/tools/debugger/).
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The output should look like this:
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[](https://www.youtube.com/watch?v=nn75gWDhHn0)
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