[Flower carving hands-on] Interesting and fun music visualization series projects (30)--P6 LED unit board

eagler8

[Flower carving hands-on] Interesting and fun music visualization series projects (30)--P6 LED unit board [Copy link]

 

I suddenly had the urge to do a series of topics on music visualization. This topic is a bit difficult and covers a wide range of areas. The related FFT and FHT algorithms are also quite complicated, but I still plan to start with the simplest ones, do some experiments, try various solutions patiently, gradually accumulate some useful music spectrum visualization materials, and strive to form some practical and fun music visualizer projects.

Find the two P6 LED unit boards, which have 512 bright RGB LEDs arranged in a 16x32 grid on the front.

lugl4313820

How is this driven? I look forward to the wonderful program. How come the OP has so many good things?

吾妻思萌

It would be best to make an animation of "You are so beautiful" if I can get the data of that dot matrix~

eagler8

lugl4313820 posted on 2022-11-3 17:58 How is this driven? I look forward to the wonderful program. How come the OP has so many good things!

It was also the first time I started looking up information and trying to figure out how to...

eagler8

Azuma Si Meng posted on 2022-11-3 18:41 It would be best to make an animation of you being too beautiful. If possible, I can get the data of that dot matrix~

This size is too small, it is 32X16, and it is best to play animations at 64X64. I plan to learn it later and start with the simple ones first. Haha

eagler8

Main parameters of indoor P6 full-color LED display unit board
Specifications Pixel: 32X16
Pixel density: 27777 dots/㎡,
dot spacing: 6mm;
Brightness ≥1200cd/㎡;
Optimal viewing angle (H/V): 120 degrees horizontally, 120 degrees vertically;
Peak power: 1000W/㎡;
Operating power: 500W/㎡;
Blind spot rate: less than one in ten thousand;
Frame change frequency: ≥60 frames/second;
Working voltage: 5V regulated power input,
working current: 2A
Continuous working time (hours): ≥7×24hrs, supporting continuous uninterrupted display;
Mean time between failures (hours): ≥10000;
Service life (hours): ≥100,000; Working environment temperature (degrees): -20～+50;
Working environment humidity: 10%～90%
Unit board size: 192 mm x 96 mm x 12 mm (7.6 inches x 3.8 inches x 0.5 inches)
with IDC Panel weight with cables and power cord: 250 g
Data logic level input: 5V
Panel interface: 12 digital pins (6 bit data, 6 bit control), full color HUB75 interface
Scan rate: 1/8
Indoor display: 150 degree visibility
Display is "linkable" - connect one output to the next input.

eagler8

eagler8

eagler8

To do this experiment well, one of the more important things is to first understand the data interface on the unit board. Initially, it is a full-color HUB75 interface.

eagler8

HUB75 is one of the communication interfaces of LED unit board. It is also called full color 75 or simply 75 port in China. There are some variants, but they are similar.

A, B, C, D, E are row signals, and E signal is not needed when it is less than or equal to 16 scans; CLK (some boards are also written as SCLK) is the clock signal; LE (some boards are also written as LAT) is the data latch signal); OE is the enable signal; R1, G1, B1 and R2, G2, B2 are two groups of data signals. The HUB75 interface found is as shown below.

吾妻思萌

eagler8 posted on 2022-11-3 19:14 This specification is too small, it is 32X16, and it is best to play animations in 64X64. I plan to learn it later, and start with the simple ones first, hehe

This is connectable, right?

I remember that the outdoor super large screen is a dot matrix version that is spliced together.

吾妻思萌

Azuma Simeng published on 2022-11-4 08:32 This can be spliced, right? I remember that the outdoor super large screen is a dot matrix version and then spliced

If there is a 64x64 later, please post a message to teach us.

eagler8

Azuma Simeng posted on 2022-11-4 08:40 If there is 64x64 later, please remember to post a message to teach us.

Thank you for the encouragement, teacher

eagler8

The driving principle of the unit board
　　LED unit board is a dot matrix of a large number of monochrome or tricolor LEDs, with scanning drive, generally the rows and lines share the cathode, and the single-column monochrome LEDs share the anode, and a dedicated chip is used for constant current drive. The so-called scanning drive means that the data lines of each column are shared, and only one row of the unit board is selected and lit at the same time, and the whole screen is displayed through fast scanning and human visual retention. Some well-made unit boards provide built-in afterglow and blanking functions. When scanning other rows, the previously lit rows will continue to light up, and when rescanning the current row, the pixels that should not be lit will be forced to turn off, so as to reduce the flicker of the screen and improve the display effect of the picture.

The row selection signal of HUB75 operates in the same way as the address line of the memory. It uses multiple address lines to combine the high and low levels to form the binary digits, and then the combined signal of n address lines is converted into a row selection signal of 2^n select 1 through a decoder. The various variants (or implementations) of the HUB75 interface are basically derived from this. Generally, the socket of HUB75 uses a 16P simple horn socket. The following is a schematic diagram of the interface:

Note the three pins 9, 10, and 11, named A, B, and C respectively. These three lines are the three bits of the 3-bit address lines A0, A1, and A2. In the internal implementation of the unit board, a 3-8 decoder is used to convert the binary combination of the high and low levels of the three input address lines into the selected state of one of the 8 output chip select lines. For example, when the level values of these four bits are H, L, and L respectively, it means that the current row address is 001b, so address line 1 (that is, representing the second row) is selected, and the others are unselected. Due to the differences in the specific internal design of the manufacturer, the row selection activation state may be high or low, so the specific level cannot be determined here, only which line is in the activated state. Since only one of the 8 row selections is activated at the same time, that is, 1/8 of the rows are being lit at the same time, this scanning method is called 1/8 scanning, and the industry abbreviation is "8 scanning".

　　Variants are generated from this. Some unit boards have less than 8 rows and do not need so many address lines, so the unnecessary address lines will be left vacant or grounded. For example, the unit board with 1/4 scan will leave the C pin 11 vacant and only use 2 address lines. The unit board with 1/32 scan will use the 12th and 6th pins as the D and E signals, i.e. the fourth and fifth bits of the binary row address, and use a 5-32 decoder to provide 32 row address lines for a wider range of scanning. At this time, the most commonly used variant of HUB75 is formed - HUB75E.

eagler8

About the communication interface of LED dot matrix screen unit board——the pit of HUB75

Because the HUB75 interface standard lacks clear specifications, some manufacturers do not transmit data completely in the above format. Take the first unit board I bought as an example. Although it is called the 1/32 scan HUB75, its row selection signal is not a standard 5-bit address line, but the 32 row selection lines of each half are connected to a serial input and output shift register, and the three signal lines ABC are used as the data, clock, and latch signals of the shift register, which is equivalent to directly integrating the simplified version of the row selection above into the unit board, which directly caused all the information I found about HUB75 to fail. Finally, I found the manual according to the chip model, and used a multimeter to test the solder joints one by one to find out the routing before I figured out the driving principle of this unit board. When asking the seller if there is any information, the seller only said that it is not compatible with the controllers on the market (all sellers say this, I don’t know if it is to make you buy their controllers), and does not provide any technical support at all. This is the biggest pit-before you get the unit board, you will never know how to use it.

References
　　: https://github.com/hzeller/rpi-rgb-led-matrix/issues/956

　　https://bikerglen.com/projects/lighting/led-panel-1up/

　　https://www.sparkfun.com/news/2650

chenhao7208

Awesome, learn from the masters...

eagler8

HUB75 interface definition for reference

eagler8

chenhao7208 posted on 2022-11-5 06:49 Awesome, learn from the big guys. . .

Not great, this is my first time using this unit board, I can't find the way, I can only post while looking up information and learning, haha

eagler8

吾妻思萌

chenhao7208 posted on 2022-11-5 06:49 Awesome, learn from the big guys. . .

Not awesome, this is my first time using this unit board, I always can't find the north, I can only post while looking up information and learning, hehe

When I first came into contact with Pi, I was also lost. Now it’s different. I don’t play it anymore . Hahaha