16 · Existing devices: mini4L

The mini4L is the direct predecessor of the Complete. It's no longer sold, but remains fully supported – so if you own one, you're in the right place. So this handbook doesn't explain everything twice, this chapter deliberately limits itself to the differences from the Complete. Everything not mentioned here – and that's by far the largest part, from operation to the web interface – works on the mini4L exactly as described in the other chapters.

What sets the mini4L apart

Unlike the Complete, which combines everything on one board, the mini4L consists of two parts: a carrier board and a plugged-in developer board on top of it (a purpose-built D32 Pro board, see forum #1109, German-language). The firmware build target is accordingly called lolin_d32_pro_sdmmc_pe. It's introduced and discussed in forum #1661 (German-language).

Pinout and SD-MMC

In practice, the actual ESP32 GPIOs are largely identical to the Complete: I²S on 25/27/26, the RFID SPI lines on 21/18/23/19, RFID_BUSY on 33 and RST on 22, the encoder on CLK 34 / DT 39, the LED on 12, wakeup and port-expander interrupt on 36, battery measurement on 35, and the IR receiver on 5. The SD card runs in SD-MMC mode (1-bit) via CLK 14, CMD 15, and D0 2. The Next, Prev, and Play/Pause buttons also sit on port-expander channels 102, 100, and 101, just as on the Complete.

The differences are limited to a few port-expander channels:

Signal	mini4L	Complete
Amplifier enable (GPIO_PA_EN)	PE 108	PE 113
Encoder button	PE 103	PE 105
Button 4 / 5	PE 104 / 105	PE 103 / 104
Headphone detection (HP_DETECT)	PE 107	PE 108
Power (peripheral cutoff)	PE 115	PE 114

On the mini4L, the PN5180 IRQ is disabled by default (value 99); for LPCD, you'd set it to GPIO 32.

Firmware and operation

You build the firmware with the lolin_d32_pro_sdmmc_pe target – otherwise chapter 13 applies unchanged. In everyday use, the most important difference ultimately comes down to a hardware detail: on the mini4L, power supply runs through a linear regulator (LDO) instead of the Complete's buck/boost regulator. What that means is explained in detail in chapter 3 → power supply. Operation and the web interface are fully identical to the Complete.