Guide: BIGTREETECH MINI-12864 V2.0 LCD with OSCR V5

[Retroteck]

Using a BIGTREETECH MINI12864 V2.0 screen with the OSCR v5 Cart Reader

Status: works on existing v5 hardware after three small but varying difficulty mods
Tested on: BTT MINI12864 V2.0, OSCR HW5, firmware branch v2lcd-final

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Why have this guide

MKS Mini12864 V3.0 displays have become noticeably scarcer and more expensive. Depending on where in the world you are BIGTREETECH MINI12864 V2.0 can be cheaper, more widely stocked, or already sitting around in a parts bin.
I believe it also gives future builders a pragmatic fallback and keeps costs or wait time down with just a few hardware tweaks and one firmware flag.

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1 – Flip the headers

image courtesy vorondesign https://docs.vorondesign.com/

The EXP1 / EXP2 shrouded connectors are keyed the opposite way to OSCR.

1. Using Tweezers or a spudger slip under and lift both 10-pin header shrouds
2. Rotate them 180 ° (keys now face towards the bottom of the PCB)

2 – Feed 3V to the OSCR

The LCD carries its own 1117-3.3 LDO but leaves EXP2 Pin 9 (originally Pin 2) unconnected.

• Solder a short wire from the LDO output pad (see photo)
  to EXP2 pin 9 (was “NC” before flipping the header).
  Now the OSCR receives a clean 3V rail from the LCD module.

3 – Keep the LCD quiet during flashing

When the AVR is being programmed, the LCD still drives MISO (D50). While technically optional you would need to unplug EXP 2 in order to upgrade/reflash the OSCR Firmware

• Lift Encoder knob off
• Fit R1 = 10 kΩ (0805 / 0603) prevents D50 from interrupting avrdude during reset.
• IMPORTANT: R7 MUST be unpopulated.

4 – Flash the firmware

1. Clone or download my branch → https://github.com/Retroteck/cartreader/tree/v2lcd-final (Ideally this would merge/PR with the main branch but we'll see.)

2. Copy Cart_Reader/Cart_Reader.ino and Config.h into your Arduino sketch folder

3. In Config.h uncomment

   #define V2LCD        // BTT MINI12864 V2.0 support
   

Summary:

1. Flip EXP1 / EXP2 shrouds 180°
2. Solder wire from LDO output to EXP2 Pin 9
3. Install 10kΩ resistor at R1 (0805 or 0603) Optional and could be solved in firmware.
4. Flash firmware with #define V2LCD enabled in Config.h

Reading 3v GBA Cart

After the modifications it can be installed and used just like the MKS mini 12864 V3 LCD module.

Firmware:
The firmware changes are minimal and related to the encoder as well as Neopixel ordering. in addition, the changes require only a config flag, meaning those currently using the MKS LCD would not need to enable anything differently, only if using the BTT LCD.

Thanks, and my apologies if this is in the wrong place.

[Ancyker]

I was working on this too, but I did it quite a bit differently because I'm rewriting the menu interface entirely.

Some snips from that:

#if defined(OPTION_BTN_PULLUP)
  PORTG = (1 << 2);
#else
  PORTG &= ~(1 << 2);
#endif

enum PIXEL: uint8_t {
#if OPTION_NEOPIXEL_ORDER == 1
  PIXEL_BG,
  PIXEL_BTN1,
  PIXEL_BTN2,
#elif OPTION_NEOPIXEL_ORDER == 2
  PIXEL_BTN1,
  PIXEL_BTN2,
  PIXEL_BG,
#endif
};

I did not enable pullups on the rotary.

[Retroteck]

Looks succinct, I can tell it's going to be quite modular.

I'll also mention you can add a 10k resistor from the Encoder pin 2 to VIN on the LDO (Only on BTT Screens) and create a pullup that prevents floating or phantom input, and then obviously you wouldn't need the firmware pullups. With the exception of the pixel order would make this a direct drop in for MKS V3 LCD.