Custom Allwinner H616 board: AP6212 doesn’t enumerate on SDIO with WL_REG_ON high. Schematic review request

Hi all,

I’ve designed and built a custom H616 board using the Orange Pi Zero 2W schematic as a reference, but with an AP6212 for Wi-Fi/BT. The board boots the Orange Pi Zero 2W image to a login prompt, with DRAM, HDMI and UART working, but the AP6212 never appears on SDIO.

The AP6212 section of the schematic is attached.

Setup

• SoC: Allwinner H616

• Wi-Fi/BT: AP6212 on SDC1 (4021000.mmc)

• WL_REG_ON: PG18

• OS: Orange Pi OS (Arch), Zero 2W image with a custom DTB

• brcmfmac, the Broadcom firmware and the AP6212 NVRAM are present on the image

What I’ve tried

• mmc-pwrseq with ext_clock

• mmc-pwrseq without a clock

• Holding WL_REG_ON high with a regulator-fixed on PG18

With WL_REG_ON confirmed high, the SDIO scan still times out and the module doesn’t enumerate.

Measurements

• VBAT: [value]

• VDDIO: [value]

• SDC1 I/O voltage: [value]

• WL_REG_ON timing relative to VBAT/VDDIO: [details]

• LPO (32.768 kHz) at the module pin: [frequency / amplitude / not present]

• CLK activity on SDC1 during the scan: [yes/no, frequency]

Other details that may matter

• The kernel has no RTC 32 kHz clock provider (SUN6I_RTC_CCU=m), so the LPO may not be running.

• The image was built for a UWE5622, so it also ships those Unisoc drivers.

• I see a kernel oops about 57 s into boot, possibly from those drivers. I can’t yet say whether it’s related.

Where I’d appreciate feedback

1. Do you see any mistakes in the AP6212 power, VDDIO, LPO, crystal or SDIO connections, including pull-ups?

2. Will the AP6212 enumerate at all without a valid 32.768 kHz LPO?

3. Is there anything specific to moving from the Zero 2W’s Wi-Fi module to an AP6212 that I may have missed?

4. If you’ve brought up an AP6212 or similar Broadcom module on Allwinner, what turned out to be the problem?

Thanks for taking a look. I’m happy to share more of the schematic or run any measurements that would help.