MM8108-EKH01 — Morse chip never enumerates on SDIO bus (mmc1) after VBAT/VBAT_TX jumper modification

Hardware
1

Hello,

I’m running into an issue on one of my two MM8108-EKH01 kits (MMECH17 v2 carrier board on a Raspberry Pi 4): the Morse Micro chip is never detected on the SDIO bus at boot, and no wlan0 interface is created.

Context As part of an RF characterization bench, I opened the VBAT and VBAT_TX jumpers on this kit’s MMECH17 v2 to route power through a Qoitech Otii Ace for power measurements (VDDIO was left closed). Since this modification, the kit has stopped working. I have since restored the jumpers to their original position and performed a full power cycle (USB-C disconnect, not just a software reboot), but the issue persists.

Symptom

  • ifconfig -a / ip link show: no wlan0/wlan1 interface at all, only lo, eth0, and the br-ahwlan bridge (down, no-carrier).
  • morsectrl stats returns: NL80211, code -1: Invalid wiphy or interface index / Transport init failed.
  • iw list returns no wiphy whatsoever.
  • Kernel modules (morse, dot11ah, mac80211, crc7) are loaded correctly (lsmod).
  • /etc/config/wireless is identical to my second, working kit (radio0 type morse, path platform/soc/fe300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:2, band s1g, country EU).

dmesg comparison

Working kit:

[6.376214] mmc-bcm2835 fe300000.mmc: DMA channel allocated
[6.378032] mmc1: new high speed SDIO card at address 0001
[6.900083] Morse Micro Dot11ah driver registration. Version 0-rel_1_16_4_2025_Sep_18
[6.958640] morse_sdio mmc1:0001:2: morse_of_probe: Reading gpio pins configuration from device tree
[7.011429] morse_sdio mmc1:0001:2: Loaded firmware from morse/mm8108b2-rl.bin, size 456924, crc32 0xe4799c8d
[7.021540] morse_sdio mmc1:0001:2: Loaded BCF from morse/bcf_boardtype_0804.bin, size 2081, crc32 0xa80ae47b

Faulty kit:

[6.382078] mmc-bcm2835 fe300000.mmc: DMA channel allocated
[6.957878] Morse Micro Dot11ah driver registration. Version 0-rel_1_16_4_2025_Sep_18
[7.006428] morse micro driver registration. Version 0-rel_1_16_4_2025_Sep_18
[7.013666] usbcore: registered new interface driver morse_usb

On the faulty kit, the mmc1: new high speed SDIO card at address 0001 line never appears. The fe300000.mmc controller (the bus dedicated to the Morse chip, separate from the boot microSD reader fe340000.mmc) initializes fine on the Raspberry Pi side, but no card ever responds on it — no error message, no explicit timeout, just a complete absence of enumeration. As a result, morse_sdio never binds, no firmware is loaded, and no radio interface is created.

What I’ve already checked

  • Kernel modules present and loaded (lsmod | grep morse).
  • UCI configuration /etc/config/wireless valid and identical to the working kit.
  • VBAT/VBAT_TX/VDDIO jumpers restored to their original position.
  • Full power cycle performed (USB-C disconnect, not just a software reboot).
  • The second kit, running the same firmware/image, works normally.

My question Does a complete absence of SDIO detection (no mmc1: new high speed SDIO card line) after VBAT/VBAT_TX jumper manipulation point to a permanent chip/module fault (e.g. damage from a power interruption while running), or are there other hardware-level checks worth doing first (RESET_N timing, SDIO line integrity, etc.) before concluding the module is defective? Is there a way to probe the chip’s state more precisely (JTAG, test points) to confirm a hardware fault rather than a software enumeration issue?

Thanks in advance for your help.