Bluetoothlaz - Installation and example comments
lazarus / 32-Linux

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TopCat · 2021-01-11 19:38

I've had some issues installing the <bluetoothlaz> package and running
the examples under Lazarus 2.0.10, fpc 3.0.4 and Raspian OS.
Ref: https://wiki.lazarus.freepascal.org/Bluetooth
Under the heading "Installation", I think a step may have been left
out from the statement "Choose the bluetooth/bluetoothlaz.lpk and open
it. That's all. The IDE now knows the package."
When the file is opened, a dialog appears. I found I had to Compile
the file then Use | Add to project. Once that was done Lazarus
recognized the package.
This is probably obvious to experienced users but I'm not one of them.
I then tried to run the examples. I got numerous errors of clashing
types and I can't understand the statement  " c_close(device_sock);"
at the end of the FindBlueToothClick event handler, which caused an
error. I'm still learning the differences between fpc Pascal and
Delphi but Lazarus didn't recognize "C_Close". I wonder if it is a
typo?
Can anyone guide me towards a working example of code that
demonstrates how to identify and connect to a Bluetooth device (it's a
serial mini-printer)? I've connected to it via the Raspian UI and sent
data successfully using LazSerial methods. The bit I need is how to
identify the bluetooth printer and connect to it directly through code
without using the Raspbian UI.
Many thanks to anyone who can help a newbie at this.

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af0815 · 2021-01-12 05:44

I have a inofficial fork here https://github.com/afriess/bluetoothlaz.
I have one sample running with a Bluetooth RFID / Barcode Reader
running well. Running on Debian Buster and actual Raspbian.

The error on c_close is normaly before. If you call close it popup,
have you looked if the handle is valid in the debugger ? One goal is
to have all the needed parts for bluetooth must be installed with sudo
apt-get install libbluetooth-dev to run the sample code correct.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
Bluetooth, unixtype, Sockets; { TForm1 } procedure
TForm1.BuFindBluetoothClick(Sender: TObject);var device_id,
device_sock: cint; scan_info: array[0..127] of
inquiry_info; scan_info_ptr: Pinquiry_info; found_devices:
cint; DevName: array[0..255] of Char; PDevName: PCChar; RemoteName:
array[0..255] of Char; PRemoteName: PCChar; i: Integer; timeout1:
Integer = 5; timeout2: Integer = 5000;begin // get the id of the first
bluetooth device. device_id := hci_get_route(nil); if (device_id < 0)
then   raise Exception.Create('FindBlueTooth: hci_get_route') else 
 writeln('device_id = ',device_id);  // create a socket to the
device device_sock := hci_open_dev(device_id); if (device_sock < 0)
then   raise Exception.Create('FindBlueTooth: hci_open_dev') else 
 writeln('device_sock = ',device_sock);  // scan for bluetooth devices
for 'timeout1' seconds scan_info_ptr:=@scan_info[0]; FillByte(scan_inf
o[0],SizeOf(inquiry_info)*128,0); found_devices :=
hci_inquiry_1(device_id, timeout1, 128, nil, @scan_info_ptr,
IREQ_CACHE_FLUSH);  writeln('found_devices (if any) =
',found_devices);  if (found_devices < 0) then   raise
Exception.Create('FindBlueTooth: hci_inquiry') else     begin     
 PDevName:=@DevName[0];       ba2str(@scan_info[0].bdaddr, PDevName); 
     writeln('Bluetooth Device Address (bdaddr) DevName =
',PChar(PDevName));        PRemoteName:=@RemoteName[0];       // Read
the remote name for 'timeout2' milliseconds       if (hci_read_remote_
name(device_sock,@scan_info[0].bdaddr,255,PRemoteName,timeout2) < 0)
then         writeln('No remote name found, check timeout.')     
 else         writeln('RemoteName = ',PChar(RemoteName));   
 end;  hci_close_dev(device_sock);end; 

But the code in  http://sourceforge.net/projects/lazarus-
ccr/files/Bluetooth/ is imho more complete than the wiki code (and the
code in my inoffcial fork is actual running on some Raspis)

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TopCat · 2021-01-12 14:08

Thanks af0815, your code worked.d
The original code worked after I changed the last statement of
btnFindBluetoothClick from  <c_close(device_sock);> to your
<hci_close_dev(device_sock);> and added <unixtype> to the uses clause.
That appears to be missing from the original samples at:
https://wiki.lazarus.freepascal.org/Bluetooth.
My next challenge is to figure out how to connect to the Bluetooth
printer so I can send text to it. I've tried the code in procedure
ConnectRFCOMMClick taken from the original sample.  Although this
runs, I haven't figured out how to relate the output from
BuFindBluetoothClick to the settings needed in ConnectRFCOMMClick to
output text to my printer. I've changed the value assigned to bt_addr,
the device address, to the address of my printer. If I set <channel>
to the value of the device_sock generated by BuFindBluetoothClick (12)
, the procedure is unable to connect. By experiment I found that
setting <channel> to 1 executed the code to send a message but nothing
got through to the printer (which is switched on!).
I was hoping that ConnectRFCOMM would make a serial connection to the
bluetooth printer and enable me to send further text by outputting to
e.g. /dev/rfcomm0 or similar.
I'd be grateful for any insights or words of wisdom you can offer.

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af0815 · 2021-01-12 14:57

In the complete sample in the git you have a line with cnt:=
fprecv(s,@bt_message, 1024, 0) if you change this to fpwrite you can
send the messagedata to the device.

In my application i have put all together in a thread to send command
to the Scanner and read the data depending if i adressed the rfid
reader or the barcode part of the scanner. You have no device in
/dev/rfcomm. All the communication must be done by fprecv and fpwrite,
no com emulation by rfcom-driver is made.

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TopCat · 2021-01-13 17:21

Andreas,
Thanks for your help. I made use of your code from
https://github.com/afriess/bluetoothlaz and changed the line
cnt:= fprecv(s,@bt_message, 1024, 0);
to
cnt:= fpsend(s,@bt_message, 1024, 0);
as fpwrite does not appear to be supported.
The good news is that it sent data to the printer  . Unfortunately,
there was a lot of it, all in hex 
I've tried code like this to send a string to the printer but without
success. Just lots of hex.
  if status = 0 then
    begin
     msg := 'Here is my test output' + #13#10;
     cnt := fpsend(s, @msg, sizeof(msg), 0);
     if cnt = -1 then
       Memo1.Lines.Add('Error occured');
     // close socket after message is sent
     fpshutdown(s, 0);
     Memo1.Lines.Add('end');
    end; 
I've obviously misunderstood the (limited) explanation of the fpsend
function and / or handling the mapping of the string to the buffer.
I can achieve what I want by using the Raspbian Bluetooth Manager to
create a rfcomm serial connection to the printer, then simply run this
code to print out a string: lsPrintr is a TLazSerial component.
procedure TMainForm.btnBluetoothClick(Sender: TObject);
begin
  if lsPrinter.Active = True then
    lsPrinter.Close;
  lsPrinter.BaudRate:= br__9600;
  lsPrinter.Device := '/dev/rfcomm0';
  lsPrinter.Open;
  lsPrinter.WriteData('Test output' + #13#10);
end;
I was hoping to avoid needing (others) to use the Bluetooth Manager to
create a connection to the printer before running my code but it looks
like the simplest way to do it, unless you can offer any additional
thoughts?
Many thanks for your support with this. It is appreciated.
Terry

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af0815 · 2021-01-15 11:41

This a complete threaded code from a running sample, which is reading
and writing to/from a RFID Reader. The reason for this is, rfcomm is
not built automatic if the communication direktion is not the default.
I have tested this with 2 RasPis. On one the rfcomm is built on the
other not. One must be the initator and one the responder. This is
only the logical sight, it have nothing to do with the
transferdirection of the data later.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i const 
FIONREAD = $541B;  FIONBIO  = $5421;  FIOASYNC = $5452; procedure
TBTReadThread.Execute;var readlen:cint32; writelen:cint32; bt_msg:
string; FDS : Tfdset; watchdog: integer; TimeV:
TTimeVal; timeout:integer;begin  FInLoop:=false;  if DummyCmd = ''
then    DummyCmd:= '.ec -x'#13; // Set echo default als
Dummycommando opt := SizeOf(loc_addr); //remote device address bt_addr
:= FDevice; //allocate socket s := fpsocket(AF_BLUETOOTH, SOCK_STREAM,
BTPROTO_RFCOMM); //channel that destination device is listening
on channel := 1; loc_addr.rc_family :=
AF_BLUETOOTH; loc_addr.rc_bdaddr := bd_addr; loc_addr.rc_channel :=
channel; str2ba(@bt_addr, @bd_addr); loc_addr.rc_bdaddr :=
bd_addr; Debugln('Trying connection to ', bt_addr);  status :=
fpconnect(s, @loc_addr, opt); if status <> 0 then begin   res:=4; 
 MustDie:= true; end; Debugln('channel: ', IntToStr(channel), '
 result: ', IntToStr(status)); try   bt_msg:='';   Owner.AktData:=''; 
 watchdog:= 0;   while not MustDie do begin     FInLoop:=true;   
 try       res:= FpIOCtl(s,FIONREAD,@readlen);     
 //Debugln('FpIOCtl=', IntToStr(res), ' Cnt=', IntToStr(readlen));   
 except       MustDie:= true;       res:=1;       continue;     
 //Synchronize(@CallStatus);     end;     if (res <> 0) then begin   
   Synchronize(@CallStatus);     end;     if (res = 0) and (readlen >
0)  then begin       SetLength(bt_msg,readlen);       cnt:=
fprecv(s,Pchar(bt_msg), readlen, 0);       {$ifdef
DEBUG}DebugLn('after fprec', ' cnt=',IntToStr(cnt));{$endif}       if
cnt <> 0 then begin         Owner.AktData:= Owner.AktData + bt_msg;  
     Synchronize(@CallEvent);       end;     end;     if Length(FData)
> 0 then begin       writelen:=
FpWrite(s,pchar(FData),length(FData));       if writelen=Length(FData)
then begin         FData:='';         {$ifdef DEBUG}DebugLn('FpWrite
ok=', IntToStr(writelen));{$endif}       end       else         if
writelen= -1 then begin           DebugLn('Error after FpWrite');    
     MustDie:= true;           res:=3;           continue;       
 end         else begin           DebugLn('Problem after FpWrite
=',IntToStr(writelen));         end;     end     else begin     
 inc(watchdog);       if watchdog > (FCheckTime*10) then begin       
 watchdog:=0;         writelen:=
FpWrite(s,pchar(DummyCmd),Length(DummyCmd));         if writelen= -1
then begin           DebugLn('Watchdog Error after FpWrite');        
 MustDie:= true;           res:=4;           continue;         end   
    else begin           {$ifdef DEBUG}DebugLn('Watchdog FpWrite ok=',
IntToStr(writelen)); {$endif}         end;       end;     end;   
 Sleep(100);   end;   Synchronize(@CallStatus); finally 
 FInLoop:=False;   // close socket   fpshutdown(s, 0); 
 CloseSocket(s);   Terminate; end; Debugln('end');end;

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TopCat · 2021-01-16 15:32

PROBLEM SOLVED 
Andreas, I'd almost given up, particularly with the thought of getting
into threads that I have little experience of. However, I extracted
and modified a section of your TBTReadThread.Execute code and inserted
that to replace part of the code in your example ConnectRFClick. In
case it is of use to others, I've shown the modified ConnectRFClick
method below.
With Buetooth turned on, running the ConnectRFClick procedure printed
the string FData directly to the printer. No other steps were needed.
A big THANK YOU for all your support and your patience.
TerryCode: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.ConnectRFClick(Sender: TObject);var  loc_addr: sockaddr_rc; 
opt: longint;  s, status: unixtype.cint;  bd_addr: bdaddr_t;  channel:
byte;  bt_addr: array[0..17] of char;  //bt_message: array[0..1023] of
char; //Variable not used  //cnt: ssize_t; //Variable not used 
{Additional declarations}  FData: string;  writelen: integer;begin 
opt := SizeOf(loc_addr);  //remote device address  //bt_addr :=
'00:07:80:66:0A:5E';  bt_addr := '00:15:0E:E4:03:49'; {my printer
address}  //allocate socket  s := fpsocket(AF_BLUETOOTH, SOCK_STREAM,
BTPROTO_RFCOMM);  //channel that destination device is listening on 
channel := 1;  loc_addr.rc_family := AF_BLUETOOTH; 
//loc_addr.rc_bdaddr := bd_addr; //Not needed. Same code 3 lines
down.  loc_addr.rc_channel := channel;  str2ba(@bt_addr, @bd_addr); 
loc_addr.rc_bdaddr := bd_addr;  writeln('Trying connection to ',
bt_addr);   status := fpconnect(s, @loc_addr, opt);  writeln('channel:
', channel, '  result: ', status);   FData := 'Lets try printing
this...';  FData := FData + #13#10 + 'and one more line...';  FData :=
FData + #13#10; {Add CRLF to get output}  if status = 0 then    begin 
    {Code extracted and adapted from procedure TBTReadThread.Execute; 
     Successfully sends FData string to the Bluetooth printer}      if
Length(FData) > 0 then        begin          //writelen:=
FpWrite(s,pchar(FData),length(FData));          writelen:=
fpsend(s,pchar(FData),length(FData), 0);          if
writelen=Length(FData) then            begin              FData:=''; 
           writeln{DebugLn}('FpWrite ok=', IntToStr(writelen));      
    end          else            if writelen= -1 then             
begin                writeln{DebugLn}('Error after FpWrite');        
      //MustDie:= true;                //res:=3;               
//continue;              end            else              begin      
        writeln{DebugLn}('Problem after FpWrite
=',IntToStr(writelen));              end;        end;  (*    cnt:=0; 
 while cnt >= 0 do    begin      bt_message := '';      //cnt:=
fprecv(s,@bt_message, 1024, 0);      cnt:= fpsend(s,@bt_message, 1024,
0);      if cnt = 0 then      begin        writeln('leer');      end 
   else        Write(bt_message);    end;  *)    // close socket after
message is sent    fpshutdown(s, 0);    writeln('end');  end;end;

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af0815 · 2021-01-16 16:22

The threaded version is not so complicaded. The execute is the major
part, allother is only tranfer the data thread safe. The execute can
send data and receive and do a alive with the dummy command to detect
if the connection is broken. This was one of my troubles to detect
safe, if the connection is broken.

If the connection is detected as broken, the not shown code handle
tis, look for a device and reconnect it, show the user that the
connection is broken and ...

This is the reason for the more complex code.

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TopCat · 2021-01-16 16:47

Andreas,
Understood. I don't need to deal with two-way data transfer by
Bluetooth, so I hope that my code will be adequate. We'll see
I've learnt quite a lot about Linux, Lazarus and Free Pascal while
trying to solve this problem, in addition to the specifics that you
have helped with. Thank you for your time.