RGB LED Serial Driver (WS2812, SK6812, etc.)
NeoPixels are individually addressable RGB LEDs that integrate the control circuit and the RGB chip into a single package. For example, the WS2812B integrates these components into a 5050 package. They are known for their simplicity in wiring (single-line data transmission) and their ability to display 16,777,216 colors (256 brightness levels per primary color).
This library provides an Ada driver for various serial RGB LEDs, often referred to as NeoPixels.
This library currently supports the following LED types:
Add neo_pixel as a dependency to your crate with Alire:
To use the Neo_Pixel library, you first need to define the types for pulse width, pulse period, and the time interval (base frequency) in which these values are expressed. You also need to select the specific LED chip you are using.
For example, let's assume you're using a 32-bit unsigned integer type (Interfaces.Unsigned_32) and the pulse width/period are expressed with a precision of 0.1 microseconds (which corresponds to a frequency of 10MHz). In this scenario, you'll also need an array type for Interfaces.Unsigned_32 to encode a batch of pulse widths.
Now, you can create an instance of the generic package:
package WS2812 is new Neo_Pixel.Generic_LED_Strip (Pulse_Width => Interfaces.Unsigned_32, Index => Positive, Pulse_Width_Array => Unsigned_32_Array, Base_Frequency => 10_000_000, -- Your base frequency, 10MHz here Chip => Neo_Pixel.WS2812);
Once your system is ready to transmit a batch of data, you use the WS2812.To_Pulses function. This function takes the color of a single pixel and returns an array of 24 pulse widths (representing 3 color components, each with 8 pulses). After assembling the desired length of pulse data for all your LEDs, the user is responsible for transmitting this pulse array to the hardware device.
Pixel : Neo_Pixel.Neo_Pixel.Pixel := (Red => 123, Green => 45, Blue => 67); -- The color of next pixel to control Batch : Unsigned_32_Array := WS2812.To_Pulses (Pixel); -- Corresponding 24 pulse width batch encoded in 0.1 us scale begin -- Transfer Batch to the led using your DMA and PWM timer configured -- to 800kHz pulse period.
After transmitting the pulse values for all LEDs, a low-level signal pause (a reset pulse) must be maintained to properly latch the data in the LEDs. For the WS2812B, this low voltage reset code must be above 50µs.
Two complete example projects are provided to demonstrate the library's usage on an STM32F4XX-M board. The first one was built with aa_stm32_drivers.
The second examlpe uses Ada Drivers Library.
To build the examples, ensure you have Alire installed and run alr build in the corresponding dirrectory.
Make sure alr is in your PATH then launch GNAT Studio in the example directory.
Make sure alr is in your PATH.
Open the example folder in VS Code. Pre-configured tasks are available to build projects and flash (using OpenOCD or st-util). Install the Cortex Debug extension and gdb-multiarch to launch pre-configured debugger targets.
Feel free to dive in! Open an issue or submit PRs.
If you find this open source project useful, you may provide me a small support on Patreon.
This project is licensed under the Apache 2.0 License with LLVM Exceptions. See the LICENSES files for details.
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