Yeah, that was the plan. Nothing's worse than finding a dead-end link with no resolution when you really want it. Full disclosure I haven't done any stress testing or speed testing to see if its using the full 4bit bus width or not but I'll trust in it so far at least.as it's working now, post the connection scheme and your config.txt line related to the SDIO interface to others can duplicate it as well.
As mentioned in the OP, using this https://www.adafruit.com/product/4682 breakout board
Hooked up 1:1 with the SDIO pinouts for a pi4 per this https://pinout.xyz/pinout/sdio reference
And this is the config, again literally just added the dtoverlay for sdio at the end.
Code:
# For more options and information see# http://rptl.io/configtxt# Some settings may impact device functionality. See link above for details# Uncomment some or all of these to enable the optional hardware interfaces#dtparam=i2c_arm=on#dtparam=i2s=on#dtparam=spi=on# Enable audio (loads snd_bcm2835)dtparam=audio=on# Additional overlays and parameters are documented# /boot/firmware/overlays/README# Automatically load overlays for detected camerascamera_auto_detect=1# Automatically load overlays for detected DSI displaysdisplay_auto_detect=1# Automatically load initramfs files, if foundauto_initramfs=1# Enable DRM VC4 V3D driverdtoverlay=vc4-kms-v3dmax_framebuffers=2# Don't have the firmware create an initial video= setting in cmdline.txt.# Use the kernel's default instead.disable_fw_kms_setup=1# Run in 64-bit modearm_64bit=1# Disable compensation for displays with overscandisable_overscan=1# Run as fast as firmware / board allowsarm_boost=1[cm4]# Enable host mode on the 2711 built-in XHCI USB controller.# This line should be removed if the legacy DWC2 controller is required# (e.g. for USB device mode) or if USB support is not required.otg_mode=1[cm5]dtoverlay=dwc2,dr_mode=host[all]#Enable SDIO interface on GPIO22-27#periodic polling, 25MHz, 4bit width (default)dtoverlay=sdio,poll_once=off,sdio_overclock=25Statistics: Posted by jungle_jim — Tue Sep 30, 2025 12:43 am