【ART-PI expansion board】RGB LEDs_IO

1. Introduction to the author

Author: Siege Lion Chenzhe

Open source hardware homepage: Siege Lion Chenzhe-Lichuang EDA open source hardware platform (oshwhub.com)

CSDN Blog Home Page: Siege Lion Chenzhe - CSDN Blog

2. Project Introduction

RGB LEDs_IO is a full-color LED dot matrix expansion board built for ART-PI open source hardware. It adopts ART-PI standard PCB size and can be stacked with ART-PI.

Onboard resources

• Onboard 128 WS2812B-Mini-V3 intelligent external control integrated LED light sources;
• A 4-bit DIP switch is used to switch the control pin of ART-PI;
• One RTC backup CR1220-2 horizontal battery holder;
• Two horizontal patch XH2.54-3P connectors are used for cascading .
• Two 2*20P-2.54 straight plug headers (

3. Introduction to WS2812

WS2812B-Mini-V3 is an intelligent externally controlled LED light source that integrates control circuit and light-emitting circuit. It has a smaller size and its outer dimensions are the same as a 3535LED lamp bead, and each component is a pixel. The pixel contains an intelligent digital interface data latch signal shaping amplification drive circuit, a high-precision internal oscillator and a programmable constant current control part, which effectively ensures that the color of the pixel light is highly consistent.

The data protocol adopts the single-wire return-to-zero code communication method. After the pixel is powered on and reset, the DIN end accepts the data transmitted from the controller. The first 24-bit data sent is extracted by the first pixel and sent to the interior of the pixel. The data latch, the remaining data is shaped and and then forwarded and output to the next cascaded pixel through the DO port. Each time a pixel is transmitted, the signal is reduced by 24 bits. The pixel adopts automatic shaping and forwarding technology, so that the number of cascades of the pixel is not limited by the signal transmission, but is only limited by the signal transmission speed requirements.

With a port scanning frequency of up to 2KHz, there will be no flickering when captured by a high-definition camera, making it very suitable for high-speed mobile products.

With a RESET time of more than 280μs, it will not cause a false reset even if an interrupt occurs, and can support lower frequency and cheaper MCUs.

LED has the advantages of low voltage drive, environmental protection and energy saving, high brightness, large scattering angle, good consistency, low power and long life. Integrating the control circuit on the LED makes the circuit simpler, smaller and easier to install.

main feature

• The IC control circuit and the LED point light source share a power supply.
• The control circuit and RGB chip are integrated into a 3535 packaged component to form a complete externally controlled pixel.
• There is a built-in signal shaping circuit. After any pixel receives the signal, it undergoes waveform shaping and then outputs it, ensuring that line waveform distortion will not accumulate.
• Built-in power-on reset and power-off reset circuit.
• The three primary colors of each pixel can achieve 256 levels of brightness display, achieving full true color display of 16,777,216 colors.
• Port scanning frequency is 2KHz.
• The serial cascade interface can receive and decode data through a signal line.
• When the refresh rate is 30 frames/second, the number of cascades is not less than 1024 points.
• Data transmission speed can reach 800Kbps.
• The color of the light is highly consistent and cost-effective.
• It will not be damaged if the power supply is reversed .
• There is no need for any peripheral electronic components including capacitors

Mechanical Dimensions

Pin diagram

Pin function

Maximum ratings (unless otherwise stated, T _A = 25°C, V _SS = 0V)

Electrical parameters (if no special instructions, T _A =25℃, V _DD =5V, V _SS =0V)

Switching characteristics (unless otherwise specified, T _A =25℃, V _DD =5V, V _SS =0V)

LED characteristic parameters

Data transfer time

Timing waveform diagram

4. Board and frame design

Draw the following size board and frame in the CAD software according to the dimensional drawing officially given by ART-PI. The board and frame file has been imported into Lichuang EDA. Click on the picture below to obtain the PCB file of the board and frame. This is a standard size board. Frame file, based on which the user can adjust the size of the board frame to meet project needs.

5. Circuit design

The design of the circuit part of this project is not complicated. The part that needs to be considered is the port selection used by ART-Pi to control WS2812. In order to better use this ART-PI, the expansion board is designed to allow port selection, through a The 4-bit DIP switch can easily switch the control pins (PC7/PI3/PH10/PH9). At the same time, in order to more conveniently use the ART-PI external board to control the expansion board, a 3P connector is designed It is used to connect external third-party boards. The port switching circuit is shown in the figure below.

Since the selected WS2812 peripheral does not require any electronic components including capacitors, the circuit design is very simple. The LED array part circuit is shown in the figure below.

On the ART-PI board, the most distinctive feature is the two sets of 2*20P headers.

6. PCB design

The PCB design of this project focuses on the array layout of 128PCS WS2812 lamp beads. Below is a picture of the array with the completed layout.

pending upgrade""""

7. PCB proofing

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8. Expansion board test

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9. Programming

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10. Demonstration video

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