Make sure your an SD Card breakout board which breaks out all 6 SDIO signals.

Then wire the signals to the corresponding pins on your hat's gpio header, keeping the wire length as short as possible.

I also placed a 10uF 16V Cap across the GND and 3v3 rails close to the card itself.

The card already includes 75 Ohm resistors on the data lines.

First make sure you have at least 1GB of free space on your MicroSD card (you may need to use raspi-config).

Then prepare the Pi for kernel module compilation:

# Update your RaPi
sudo apt-get update && sudo apt-get -y upgrade

# Install the Prerequisites for Module Compilation & Menuconfig
sudo apt-get -y install bc rpi-update git libncurses5-dev

Modify the boot config, update firmware and kernel, and reboot:

# Modify /boot/config.txt so the sdio dtoverlay is loaded on boot.
sudo sed -i -e "/^dtoverlay.*sdio/d" /boot/config.txt
sudo sh -c 'printf "dtoverlay=sdio,poll_once=off" >> /boot/config.txt'

# Install the latest firmware and kernel
sudo rpi-update 

# reboot
sudo reboot

Install rpi-source and run it to download the kernel sources:

cd ~

sudo wget https://raw.githubusercontent.com/notro/rpi-source/master/rpi-source -O /usr/bin/rpi-source && sudo chmod +x /usr/bin/rpi-source && /usr/bin/rpi-source -q --tag-update

rpi-source --skip-gcc

Until the mainline kernel driver works properly or Atmel's own driver actually compiles we need to pull the driver from upstream:

# avoid having to dl all of linux-next
wget -r -l1 -e robots=off -nH --no-parent --cut-dirs=9 --reject="index.html" http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/plain/drivers/staging/wilc1000

Now a quick change to one of the files. The driver will fail to compile:

nano +567 wilc1000/wilc_wfi_cfgoperations.c

You should see something like this:

cfg80211_disconnected(dev, pstrDisconnectNotifInfo->u16reason, pstrDisconnectNotifInfo->ie,
                      pstrDisconnectNotifInfo->ie_len, false,
                      GFP_KERNEL);

cfg80211_disconnected(dev, pstrDisconnectNotifInfo->u16reason, pstrDisconnectNotifInfo->ie, pstrDisconnectNotifInfo->ie_len, GFP_KERNEL)

Add the driver source code to the kernel:

mv wilc1000 linux/drivers/staging && cd linux

# edit the staging Kconfig
sed -i -e "/^endif \# STAGING/d" drivers/staging/Kconfig
printf 'source "drivers/staging/wilc1000/Kconfig"\n\nendif # STAGING' >> drivers/staging/Kconfig

# edit the staging Makefile
printf 'obj-$(CONFIG_WILC1000)          += wilc1000/' >> drivers/staging/Makefile

Update the kernel configuration:

make menuconfig

Navigate to

Device Drivers ▸ Staging Drivers

Set Atmel WILC1000 SDIO (WiFi only) to M

Now for compilation:

# Run make prepare for good measure
make prepare

# Build the modules
make SUBDIRS=drivers/staging/wilc1000 modules

# If all goes well, install the modules
sudo make SUBDIRS=drivers/staging/wilc1000 modules_install
sudo depmod

Reboot and power cycle the card by removing it then reinserting it

sudo reboot

If you've made it this far, congrats! You should now be able to see 2 new devices when you run ifconfig: wlan0 and p2p0