Bluetooth audio on embedded hardware

I would really like the bluetooth-alsa project to get far enough along to really shine on embedded platforms. gumstix is the perfect little device for working this out. This device currently ships with an Infineon Singlestone PBA31307.

Status

Gumstix uses a bluetooth 1.2 adapter now, the infineon pba 31307 (bt1.2 means better cooperation with wifi)
Gumstix hardware now routes infineon PCM to xscale's NSSP i/o (PCM-clock goes to NSSP-clock, PCM-frame goes to NSSP-frame, and PCM-in/out map to the NSSPTXD/TXD)
Unfortunately, Gumstix is talking to bluetooth adapter at a fixed 115k (switching to 921k according to infineon docs does not work properly)

To-do

Complete alsa kernel driver code to deal with audio in/out through NSSP as a "regular" audio device (Craig)

Wishlist

Negotiate 921kbps connection to bluetooth adapter, needed for a2dp and sco over hci
Try sco over hci by forcing mtu values and investigating the adapter's ogf and ocf parameters (Brad)
Modify a2play to build again and so it uses usleep() instead of the rtc (Brad)

Bluegiga Class 1 bluecore4 module

Adding your own bluetooth module will allow things like full 921k data connection, SCO over HCI(*), and class 1 ranges. This adapter can do EDR, but the pxa255 UART cannot go beyond 921k unfortunately.

* To do SCO over HCI, you will need a kernel patch to avoid crashes and to maintain more consistent audio quality. I am talking with Marcel Holtmann about merging this patch upstream.

The model for this adapter is wt11-a-hci from semiconductorstore.com. Note that the data sheet referenced from semiconductorstore is old. Go directly to bluegiga for updated docs.

Wiring it up

Using GPIO48-51 as I'm suggesting here conflicts with the pcmcia pins, so plan to leave the GPIO settings alone and use HWUART through GPIO42-45 if you need pcmcia. You do this either on a module without bluetooth or by clearing GPIO7 and hoping the pins can all be used while the built-in module is held in reset.

The first thing to do after getting this module is to wire it up and try to reconfigure it from a PC so the module will use the uart/h4 interface.

Bluegiga pxa Description

1 gnd

2 3.3v regulated typical 200mA max 220mA

21 3.3v to disable spi? (I left this unconnected)

8 usb d+ for programming
9 usb d- for programming
5 rts gpio50 hwcts module uart rts->hwcts (asserted by module)
10 cts gpio51 hwrts module uart cts<-hwrts (asserted by gumstix)
26 tx gpio49 hwrxd module uart tx->hwrxd (asserted by module)
6 rx gpio48 hwtxd module uart rx<-hwtxd (asserted by gumstix)
17 reset gpio16 "PW[M]0" reset (active high)

Bluegiga	pxa	Description
1		gnd
2		3.3v regulated typical 200mA max 220mA
21		3.3v to disable spi? (I left this unconnected)
8		usb d+ for programming
9		usb d- for programming
5 rts	gpio50 hwcts	module uart rts->hwcts (asserted by module)
10 cts	gpio51 hwrts	module uart cts<-hwrts (asserted by gumstix)
26 tx	gpio49 hwrxd	module uart tx->hwrxd (asserted by module)
6 rx	gpio48 hwtxd	module uart rx<-hwtxd (asserted by gumstix)
17 reset	gpio16 "PW[M]0"	reset (active high)

Firmware settings

Making the adapter use its uart connection is done using the bccmd app from bluez utils cvs (configure with --enable-bccmd to get bccmd)

bccmd can "brick" your adapter if you make a mistake! To test things without risking this, connect both usb to a pc and the uart connected to the gumstix. (I power the gumstix from usb when doing this.) Then run

 bccmd psset -r 0x3cd 4

To set the adapter to use the uart and do a soft reset. I had to do this twice before it would actually disconnect from usb and reconnect on the uart.

Then attach to the adapter on the gumstix:

# shut down internal bluetooth
/etc/init.d/S30bluetooth stop

# switch the built-in bluetooth to BTUART for now
echo "AF1 in" >/proc/gpio/GPIO42
echo "AF2 out" >/proc/gpio/GPIO43
echo "AF1 in" >/proc/gpio/GPIO44
echo "AF2 out" >/proc/gpio/GPIO45
        
# make the "HWUART" labeled pads on the audiostix actually carry HWUART
echo "AF1 out" >/proc/gpio/GPIO48
echo "AF1 in" >/proc/gpio/GPIO49
echo "AF1 in" >/proc/gpio/GPIO50
echo "AF1 out" >/proc/gpio/GPIO51

# bring it up
echo "GPIO out set" >/proc/gpio/GPIO16
sleep 1
echo clear >/proc/gpio/GPIO16
sleep 1

# attach the adapter
/usr/sbin/hciattach -s 115200 ttyS3 csr 921600

# check for the adapter
hciconfig -a
hcitool scan

Once you are satisfied that works, cold boot everything and this time make it permanent from the pc:

 bccmd psset -s default 0x3cd 4

Bringing up CSR automatically

Modify /etc/default/bluetooth

	HCIATTACH_TYPE=csr
	HCIATTACH_START_SPEED=115200

modify S30bluetooth to set GPIO status before attempting an attach--only if NOT using pcmcia

We either need to move the bt module to BTUART (we could have two bt interfaces--hmm!)

	echo "AF1 in" >/proc/gpio/GPIO42
	echo "AF2 out" >/proc/gpio/GPIO43
	echo "AF1 in" >/proc/gpio/GPIO44
	echo "AF2 out" >/proc/gpio/GPIO45

Or... disable the bt module's GPIOs entirely (for better power efficiency, set 42 and 44 for output as long as we know they are left in hi-z by the module)

	echo clear >/proc/gpio/GPIO7

	echo "GPIO in" >/proc/gpio/GPIO42
	echo "GPIO out" >/proc/gpio/GPIO43
	echo "GPIO in" >/proc/gpio/GPIO44
	echo "GPIO out" >/proc/gpio/GPIO45

	echo "GPIO out" >/proc/gpio/GPIO12

set the appropriate GPIO pins to use the HWUART on GPIOs 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

in S30bluetooth, modprobe hci_uart and give it a chance to settle down (?)
```
	/sbin/modprobe hci_uart ; sleep 5
```

and finally, in S30bluetooth again, reset the adapter before the hciattach

	echo "GPIO out set" >/proc/gpio/GPIO16
	sleep 5
	echo clear >/proc/gpio/GPIO16
	sleep 5

It's working (woohoo)

# hciconfig hci0 revision
hci0:   Type: UART
        BD Address: 00:07:80:81:BC:3E ACL MTU: 384:8 SCO MTU: 64:8
        Build 2810
        Chip version: BlueCore4-External
        Max key size: 56 bit
        SCO mapping:  HCI
# hciconfig -a hci0
hci0:   Type: UART
        BD Address: 00:07:80:81:BC:3E ACL MTU: 384:8 SCO MTU: 64:8
        UP RUNNING PSCAN ISCAN 
        RX bytes:4577 acl:95 sco:0 events:289 errors:0
        TX bytes:2735 acl:95 sco:0 commands:80 errors:0
        Features: 0xff 0xff 0x8f 0xfe 0x9b 0xf9 0x00 0x80
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
        Link policy: RSWITCH HOLD SNIFF PARK 
        Link mode: SLAVE ACCEPT 
        Name: 'Gumstix (0)'
        Class: 0x820116
        Service Classes: Networking
        Device Class: Computer, Palm
        HCI Ver: 2.0 (0x3) HCI Rev: 0xafa LMP Ver: 2.0 (0x3) LMP Subver: 0xafa
        Manufacturer: Cambridge Silicon Radio (10)

fwiw... S30bluetooth runs echo AF1 out > /proc/gpio/GPIO12 on start but has no corresponding action in stop. This sends out a clock signal that the infineon needs apparently.