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MC/SD card howto

This is a short guide to get an MMC/SD card working with OpenWrt Kamikaze 8.09 and an 2.6 Kernel. The driver can be configured using either UCI CLI or the LuCI WebUI.

GPIO Pinouts

Description                GPIO
PIN 1, CS - Chip Select    GPIO 7
PIN 2, DI - Data In        GPIO 1
PIN 3, VSS - Ground        GND
PIN 4, VDD - 3.3 Volts     3.3 Volts
PIN 5, CLK - Clock         GPIO 3
PIN 7, DO - Data Out       GPIO 4

GPIO Solder Points

Images from PCB.



Install packages

Required packages:

  • kmod-mmc-over-gpio
  • kmod-fs-ext3/kmod-fs-ext2/…. (we use the EXT3 file system here)
  • cfdisk/fdisk (we use cfdisk here)
  • e2fsprogs

root@OpenWrt:~# opkg update
root@OpenWrt:~# opkg install kmod-mmc-over-gpio kmod-fs-ext3 cfdisk e2fsprogs

Configure GPIOs

root@OpenWrt:~# uci set mmc_over_gpio.@mmc_over_gpio[0].enabled=1
root@OpenWrt:~# uci set mmc_over_gpio.@mmc_over_gpio[0].DI_pin=1
root@OpenWrt:~# uci set mmc_over_gpio.@mmc_over_gpio[0].DO_pin=4
root@OpenWrt:~# uci set mmc_over_gpio.@mmc_over_gpio[0].CLK_pin=3
root@OpenWrt:~# uci set mmc_over_gpio.@mmc_over_gpio[0].CS_pin=7
root@OpenWrt:~# uci commit mmc_over_gpio
root@OpenWrt:~# /etc/init.d/mmc_over_gpio start
root@OpenWrt:~# /etc/init.d/mmc_over_gpio enable

Mount the MMC/SD card via fstab

To get partition mounted automatically you have to edit and change START=20 to START=98 in the /etc/init.d/fstab init script.

root@OpenWrt:~# uci set fstab.@mount[0].enabled=1
root@OpenWrt:~# uci set fstab.@mount[0].fstype=ext3
root@OpenWrt:~# uci set fstab.@mount[0].device=/dev/mmcblk0p1
root@OpenWrt:~# uci set fstab.@mount[0].target=/mnt/mmc
root@OpenWrt:~# uci set fstab.@mount[0].options=rw,sync,noatime
root@OpenWrt:~# uci commit fstab
root@OpenWrt:~# /etc/init.d/fstab restart

Using the LuCI WebUI

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doc/howto/mmc_over_gpio.txt · Last modified: 2010/09/19 10:23 by realopty