[Gumstix-users] Using BTUART for Bluetooth on startup: gumstix-bluetooth module stomps GPIOs

[Andrew T. <and...@gm...>]

Hi everybody,

One "gotcha" I just discovered that I thought should be shared:

I'm using a connex-bt with a breakout-gs, and I'd like to use the
HWUART for communicating with another device.  So I followed the
instructions on the wiki and in Bruce Fortnam's Jan 9 2007 post,
namely:

1) modify /etc/default/bluetooth, changing the HCI_ATTACH_TTY line:
HCIATTACH_TTY=ttyS1

2) configure the GPIO pins:
modprobe proc_gpio
# BTUART on GP[42:45]
echo AF1 in > /proc/gpio/GPIO42
echo AF2 out > /proc/gpio/GPIO43
echo AF1 in > /proc/gpio/GPIO44
echo AF2 out > /proc/gpio/GPIO45
# HWUART on GP[48:51]
echo AF1 out > /proc/gpio/GPIO48
echo AF1 in > /proc/gpio/GPIO49
echo AF1 in > /proc/gpio/GPIO50
echo AF1 out > /proc/gpio/GPIO51

I wanted this to be the default on startup, so I put the GPIO commands
into a new script called S25uarts in the /etc/init.d directory, so
that the GPIO pins would get configured before the bluetooth script
(S30bluetooth) ran.

It turns out, however, that in S30bluetooth, when the following line executes:
/sbin/modprobe gumstix-bluetooth

the GPIO assignments for [42:45] get changed back to AF3.

The workaround is simple: don't configure the GPIO pins before
S30bluetooth; instead, configure them within S30bluetooth, immediately
after the /sbin/modprobe gumstix-bluetooth command.

Cheers,

- Andrew Tinka