Excellent work. I was hoping someone had already done the RFCOMM SPP layer. If I understand correctly this means we'd be able to use the cheap $2.00 BT USB modules to give our MBED bluetooth serial right??

Thanks for your contributions!!!

Yes, The RFCOMM layer follows the pattern of the other layers so the interface is as defined in Socket.h.

int Socket_Open(SOCKET_RFCOM, &s.hdr, cb, this); where s is L2CAPAddr (hci.h) containing the BT address and rfcomm channel (in psm), cb is the callback where the received data goes: void cb(int socket, SocketState state, const unsigned char *data, int len, void *userData); and 'this' is the userData pointer to the object receiving the data. Socket_Open returns the socket just opened.

Socket_Close(socket); closes the socket Socket_Send(int socket, const unsigned char *data, int len); sends a block of data of length 'len' to the peer device. True Serial compatibility would need an aditional adaptation which defines putc, getc, readable, writable and preferably some buffering.

Fantastic job implementing RFCOMM, well done!

good job :)

I am trying to receive ASCII strings from a Bluetooth GPS. Although i am reading about RFCOMM, Bluetooth protocols and connecting WII Remote i still don't understand how to receive the ASCII strings from the BT GPS.

After installing my BlueUSB on the mbed i see the following results in CoolTerm

HCI_EV_REMOTE_NAME 16: 07 FF 00 1B A4 8C 1B 08 00 42 54 20 47 50 53 00
.[33m00:08:1B:8C:A4:1B = BT GPS
.[0mReady to open ports
0 ft BT devices have been found
Passively opening socket 1 for type 3, invoking 'Listen' on 10000544 (=RFCOMMManager SocketHandler)
RFCOMM listener socket 1 for ch 1 (dlci 0x02) is assigned to slot 0

So i think that the connection is established and RFCOMM is waiting? But how to retrieve the Data? I have checked the function of the BT GPS. This transfers the Data correctly to a BT serial program running on a second computer.

So anyone can give me a tip how to carry on? Thanks.

Hi,

thanks for using blueusb :). No the connection is not established yet, the devices see each other and there is a socket on the mbed listening. What you need to know is who will initiate the connection. Right now the mbed expects the GPS to initiate the connection and is waiting on channel 1, which is mostly the correct channel. If you want the mbed to initiate the connection you need Socket_Open i.o. Socket_listen. When you are using the btserial class you need to take the other constructor (the one with the bluetooth address (of the GPS)). Have a look at this thread as well: http://mbed.org/forum/mbed/topic/2269/?page=1#comment-11562

happy to answer further questions

Wow thanks for that fast answer. But i still don'tt understand the way of how to communicate with the GPS. I would prefer to use the btserial class as the GPS is answering with strings. And changing to other BT GPS modules would mean that i'll have to compile the source again. Is there any source skeleton of how to realise this ?

Well I use it for a different purpose (the ft devices). But using the btserial class should be easy (but it is very poorly tested because I don't use it myself, it was intended as an example). Many devices work with Request/Response sequences, A device (usually the initiator) sends a request and waits for the response. GPS may be different, my GPS (serial, not USB) just spits out data in a format defined through its LCD screen. In that case look how it connects to your PC. When you create virtual comports for BT devices you van choose whether it should be for incoming or outgoing trafic (Note: both are bidirectional, it is just a matter of initiative). So if your PC uses an outgoing port (with a specific BT address) then for the mbed you also choose the constructor with the BT address. One way or the other, after the connection is established, you call readable or getc to read the incoming data and hope that there is some. Please look at the code that Rob wrote in the link I sent you.

After changing to the btserial class with the Address of the BT GPS this is my result. I have modified the Address in Robs code. Still no data from BT GPS.

HCI_EV_REMOTE_NAME 16: 07 FF 00 1B A4 8C 1B 08 00 42 54 20 47 50 53 00
.[33m00:08:1B:8C:A4:1B = BT GPS
.[0mB ready to connect
Opening socket 1 for type 3, invoking 'Open' on 10000544 (=RFCOMMManager SocketHandler)
Need to open L2CAP channel first before opening RFCOMM channel 0
Opening socket 2 for type 2, invoking 'Open' on 10000610 (=HCI SocketHandler)
Can't open l2cap 3 on 1B:A4:8C:1B:08:00
Successfully opened L2CAP channel on socket -300

-300 is the device not found error. During the inquiry the mbed builds a list of devices, the device you want to connect to must be in this list. Please look higher in the log for entries like "Inquiry Result:", I think you have the address backwards.

oops. The address was really backwards. After correcting this is the result.

RFCOMM: EA=1, C/R=1, D=0, ch=2; control=1F (P/F=1); length=0
payload: 0:
Received DM IND (1F) for dlci 4
Socket 1 has been freed
.[0mACL Read pending..

Seems it is connected now. How to get an answer from the BT GPS ?

No it is not connected. The GPS sent you a DM indication (Disconnected Mode). This typically means that there was something in the connection setup that it didn't like. Sometimes this can be solved by looking at the proposed parameters and the replies. Typically look at PN and MSC commands, there are other commands like RPN and FCOn/FCOff that the mbed does nothing or very little with. Please send me a private message with the entire log file and I'll try to find out what happened.