P4 80x40 1:10 display integration issue

[priya2212]

Hi All,

I have followed the article to wire up the P4 LED with RPI. I am facing issues in writing text and scrolling images. I have run the code using below command - sudo examples-api-use/text-example -f fonts/helvR12.bdf --led-cols=80 --led-rows=40 --led-multiplexing=0 --led-no-hardware-pulse changed it tosudo examples-api-use/text-example -f fonts/helvR12.bdf --led-cols=16 --led-rows=40 --led-chain=5 --led-multiplexing=0 --led-no-hardware-pulse But unfortunately getting the same results attached in the image.

I have gone through these forum links - Different Scan Rates / P4 80x40 10S (1:10 scan) multiplexer help and tried adding own multiplexer as recommended but not able to run the example.

Any help will be appreciated. If you need any information from my end, I would be happy answering them as early as possible.

[priya2212]

Anybody can please help me. I got the module specification from manufacturer -

[anandrajgupta]

1st thing: On the back side it is mentioned HUB75E which hints that you will have to wire up the additional "E" pin

2nd thing: You have to use the --led-slowdown-gpio=x where x= 0 to 5

3rd thing: You have to try different --led-multiplexing=x where x = 0 to 17

Try and let's see how it goes 🤔

[priya2212]

Hi @anandrajgupta, Thank you very much for your response. I am currently away from the system and would give it a try very first thing. Just to mention, I have connected E as well and follow the wiring from here - https://github.com/hzeller/rpi-rgb-led-matrix/blob/master/wiring.md

[b4rtek]

Hey @priya2212 you must modify lib/multiplex-mappers.cc by adding new mapper

class P4Outdoor80x40 : public MultiplexMapperBase {
public:
  P4Outdoor80x40() : MultiplexMapperBase("P4Outdoor80x40", 2) {}

  void MapSinglePanel(int x, int y, int *matrix_x, int *matrix_y) const {
    int shift = (y  / (panel_rows_ / 4)) % 2;
    *matrix_y = ((y / (panel_rows_/2)) * (panel_rows_/4)  + y % (panel_rows_/4));
    *matrix_x = ((x * 2) + (shift ? 0 : 1));
  }
};

(like in (https://github.com/hzeller/rpi-rgb-led-matrix/issues/49) and recompile. When u do this u are be able to use --led-multiplexing=19 Thats should help. I see u have almost same board as my, only yours is v2.0 and i have v1.0. I this this is irrelevant but i am not an expert ;)

[priya2212]

Hi @anandrajgupta and @b4rtek ,

I tested the library with your mentioned suggestions and following are the results -

Test 1. Tested it with - led-multiplexing=1 and ran the following command -

sudo ./examples-api-use/text-example --led-brightness=100 --led-cols=80 --led-rows=40 --led-chain=1 --led-pwm-lsb-nanoseconds=300 --led-slowdown-gpio=5 -f fonts/helvR12.bdf -C 255,0,0 --led-multiplexing=1
Enter lines. Full screen or empty line clears screen.
Supports UTF-8. CTRL-D for exit.
HELLO
HELLO

The strings are displayed in the first half only, not second half and due to this, when writing 2nd hello, the string got cut.

Test 2. Tested with - led-multiplexer=19 and ran the following command -

sudo ./examples-api-use/text-example --led-brightness=100 --led-cols=80 --led-rows=40 --led-chain=1 --led-pwm-lsb-nanoseconds=300 --led-slowdown-gpio=5 -f fonts/helvR12.bdf -C 255,0,0 --led-multiplexing=19
Enter lines. Full screen or empty line clears screen.
Supports UTF-8. CTRL-D for exit.
HELLO

Attached photo for git diff for your reference.

However, with led-multiplexing as 1, I got some positive results as with the python binding, I was able to scroll the text in the middle - sudo python runtext.py --led-brightness=100 --led-cols=80 --led-rows=40 --led-chain=1 --led-pwm-lsb-nanoseconds=300 --led-slowdown-gpio=5 --led-multiplexing=1

https://user-images.githubusercontent.com/20925260/213113474-592f6d27-355b-427c-83cb-b4a37a059c42.mp4

Can we change something in led-multiplexing=1 to make it work as required?