Qiangli 32x32 P10 panel with LS9931CS+DP32020A-B - no output on RP2040

1

Panel specifications:

  • Size: 32x32 pixels (P10 indoor module)

  • Driver ICs: LS9931CS (LED driver) + DP32020A-B (row decoder)

  • Address lines: A, B, C connected; D pin present but grounded on panel

  • HUB75 interface (standard 16-pin connector)

  • Photo of back: [attach your photo]

Previous working configuration: I have another Qiangli 32x32 panel with DP5135+RUL5158C chips that works perfectly using DMD_STM32 library with:

  • 3 address pins (A, B, C), D grounded

  • Shift register multiplexing configuration

  • 1/8 scan pattern

Current problem: New panel with LS9931CS+DP32020A-B gives completely black screen (no output at all) with same configuration.

What I’ve tried:

  1. Standard 1/8 scan configuration with 3 address pins (A, B, C) - no output

  2. Plain 1/16 scan with 4 address pins (A, B, C, D connected to GPIO) - no output

  3. Various DMD library patterns: RGB32x32plainS16, RGB32x32_S8_Qiangli, RGB32x32_S8_maxmurugan - none work

  4. Both regular DMD_RGB and DMD_RGB_SHIFTREG_ABC wrapper - no difference

  5. Verified all pin connections, OE, SCLK, RGB pins - all correct

Hardware:

  • Microcontroller: RP2040 (Raspberry Pi Pico)

  • Library: DMD_STM32 (ported for RP2040)

  • Pin assignments: A=GPIO6, B=GPIO7, C=GPIO8, D=GPIO9 (when connected)

Questions:

  1. Does DP32020A-B require D pin to be actively driven for 32x32 1/8 scan, or should it remain grounded?

  2. Is LS9931CS+DP32020A-B combination fundamentally different addressing than DP5135+RUL5158C requiring different scan pattern?

  3. Any known working configurations for this specific IC combination?

Any guidance would be greatly appreciated.

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2

Hi @aknsha

NO, it doesn’t require D pin.
The DP32020 is a multiplexer of shift register type, that needs only three pins (A B C) to manage a panel with any scan number.

First of all, the driver LS9931 is a new type sPWM driver, that use a fundamentally different principle of operation. This driver is not supported by the library. Moreover, the datasheet for the LS9931 chip is not publicly available, making code development difficult.

I don’t know any of them.