Hello,
Last year i worked on the RTL-SDR dongle Purebasic wrapper.
Again, many thanks to
infratec for his great help leading to the "libsdr.pbi" file.
In my post above, you can find the working example for ADSB decoding using synchronous buffer reading function (rtlsdr_read_sync) in console mode.
The prototype defined in librtlsdr.pbi is:
PrototypeC.l proto_rtlsdr_read_sync(*dev.rtlsdr_dev_t, *buf, len.l, *n_read)
The purebasic code above is mainly derived from old Delphi code concerning both synchronous and asynchronous ADSB decoding
https://sourceforge.net/projects/rtl-ad ... -xe8-port/
I wonder if it is possible to make the same thing using asynchronous buffer reading (rtlsdr_read_async), with thread and semaphore like in Delphi code.
The prototype defined in librtlsdr.pbi for asynchronous reading is:
PrototypeC.l proto_rtlsdr_read_async(*dev.rtlsdr_dev_t, cb.rtlsdr_read_async_cb_t, *ctx, buf_num.l, buf_len.l)
Here is the Delphi source code for ADSB asynchronous decoding in console:
https://github.com/randaller/rtlsdr-ads ... d_adsb.dpr
rtlsdr_read_async function declared in
rtlsdr.pas wrapper:
// RTLSDR_API int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, uint32_t buf_num, uint32_t buf_len);
function rtlsdr_read_async(rtlsdr_dev_t: Pointer; cb: Trtlsdr_read_async_cb_t; ctx: Pointer; buf_num: UINT32; buf_len: UINT32): Integer; stdcall; external rtldll;
Here are specific Delphi parts for asynchronous decoding in rtl_asyncread_adsb.dpr:
Code: Select all
var
thread_buf: array [0 .. DEFAULT_BUF_LENGTH] of Byte;
ThreadHandle: integer;
ThreadID: DWORD;
hSem: THandle = 0;
function Read(buffer: PAnsiChar; size: integer; ctx: Pointer): LongWord;
begin
if ctx = nil then
Exit(0);
// 262144 bytes in buffer
// Move(buf, ctx, size);
CopyMemory(@buf[0], ctx, size);
hSem := CreateSemaphore(nil, 1, 1, nil);
Result := 1;
end;
procedure ThreadProc;
var
len: integer;
WaitReturn: integer;
begin
while (True) do
begin
WaitReturn := WaitForSingleObject(hSem, INFINITE);
if WaitReturn = WAIT_OBJECT_0 then
begin
// writeln('thread on');
CopyMemory(@thread_buf, @buf, DEFAULT_BUF_LENGTH);
len := magnitute(thread_buf, DEFAULT_BUF_LENGTH);
manchester(thread_buf, len);
outmessages(thread_buf, len);
ReleaseSemaphore(hSem, 1, nil);
CloseHandle(hSem);
// writeln('thread off');
end;
end;
rtlsdr_cancel_async(dev);
end;
## Specific part in the Main Delphi code ##
ThreadHandle := CreateThread(nil, 0, @ThreadProc, nil, 0, ThreadID);
r := rtlsdr_read_async(dev, @read, nil, 32, DEFAULT_BUF_LENGTH);
Below is my Purebasic code. The Window console is launched without error, SDR dongle is recognized,... but no buffer data is processed.
Here are the specific asynchronous decoding parts:
Code: Select all
Global Dim thread_buf.a(block_size)
Global hThread.l
Global hSem.l
Procedure ReadBufffer(*buf, len.l, *ctx)
If *ctx=0
ProcedureReturn 0
EndIf
; CopyMemory in Delphi (Destination: Pointer; Source: Pointer; Length: DWORD)
; CopyMemory in Purebasic (*Source, *Destination, Size)
CopyMemory(*buf, @buffer.a(), len.l)
; handle semaphore
hSem=CreateSemaphore()
MessageRequester("Info","Copy realized and semaphore created", 0)
ProcedureReturn 1
EndProcedure
Procedure ThreadProc(value)
Protected len.i
Protected WaitReturn.i
Repeat
;WaitReturn=WaitSemaphore(hSem)
;If WaitReturn=0
; CopyMemory (source, destination, taille)
CopyMemory(@buffer.a(), @thread_buf.a(), block_size)
len = magnitude(@thread_buf.a(), block_size)
manchester(@thread_buf.a(), len)
outmessages(@thread_buf.a(), len)
; FreeSemaphore(hSem)
;EndIf
ForEver
;rtlsdr_cancel_async(*dev)
EndProcedure
## Specific part in the Main Purebasic code ##
hThread=CreateThread(@ThreadProc(), 0)
r = rtlsdr_read_async(*dev, ReadBuffer, 0, 32, block_size)
Here is the whole code
Code: Select all
EnableExplicit
IncludeFile "librtlsdr.pbi"
#SDR_SRATE =2000000
#ADSB_FREQ =1090000000
#SDR_GAIN =439
#PREAMBLE_LEN =16
#LONG_FRAME =112
#SHORT_FRAME =56
#MESSAGEGO =253
#OVERWRITE =254
#BAD_SAMPLE =255
#BUF_LENGTH =16*16384
Define.i i, r, n_read
Define.l dev_index
Define.i device_count
Define *dev.rtlsdr_dev_t
Define *buf
Define *n_read
Define ReadBuffer
Define cb.rtlsdr_read_async_cb_t
Global length.i = 0
Global buf_num.i = 0
Global block_size.i=#BUF_LENGTH
Global StopReadingSamples.b=#False
Global Dim pythagore.a(128,128)
Global Dim adsb_frame.a(14)
; Global Dim buf.a(block_size)
Global Dim buffer.a(block_size)
Global Dim thread_buf.a(block_size)
Global hThread.l
Global hSem.l
Global allowed_errors.i = 5
Global quality.i = 20
Global short_output.i = 0
Global verbose_output.i = 0
Global lf_counter.i = 0
Global sf_counter.i = 0
Global show_stats.b = #False
Procedure.i abs8(x.i)
If x >= 128
ProcedureReturn x - 128
Else
ProcedureReturn 128 - x
EndIf
EndProcedure
Procedure pythagore_precompute()
Protected.i x, y
Protected.f scale
Protected.a value
scale = 1.408
For x = 0 To 128
For y = 0 To 128
value=Round(scale * Sqr(x*x + y*y), #PB_Round_Nearest)
pythagore.a(x, y) = value
Next y
Next x
EndProcedure
Procedure magnitude(buf.a, len)
Protected.i i,j
Protected.a sq
; takes IQ samples. Changes in place with the magnitude value (Char/uint8_t)
For i=0 To len-1 Step 2
sq.a = pythagore(abs8(buffer(i)), abs8(buffer(i + 1)))
buffer(Int(i/2))=sq.a
Next i
;returns new buffer length
ProcedureReturn len/2
EndProcedure
Procedure.a single_manchester(a.a, b.a, c.a, d.a)
Protected bit.a, bit_p.a
; takes 4 consecutive samples, return 0 or 1, #BADSAMPLE on error
If a>b
bit_p=1
Else
bit_p=0
EndIf
If c>d
bit=1
Else
bit=0
EndIf
If quality=0
; no sanity check
ProcedureReturn bit
EndIf
If quality=5
; sanity check half-bit
If ((bit=1) And (bit_p=1) And (b>c))
ProcedureReturn #BAD_SAMPLE
EndIf
If ((bit=0) And (bit_p=0) And (b<c))
ProcedureReturn #BAD_SAMPLE
EndIf
ProcedureReturn bit
EndIf
If quality=10
; sanity check one bit
If ((bit=1) And (bit_p=1) And (c>b))
ProcedureReturn 1
EndIf
If ((bit=1) And (bit_p=0) And (d<b))
ProcedureReturn 1
EndIf
If ((bit=0) And (bit_p=1) And (d>b))
ProcedureReturn 0
EndIf
If ((bit=0) And (bit_p=0) And (c<b))
ProcedureReturn 0
EndIf
ProcedureReturn #BAD_SAMPLE
EndIf
; Sanity check two bits
If ((bit=1) And (bit_p=1) And (c>b) And (d<a))
ProcedureReturn 1
EndIf
If ((bit=1) And (bit_p=0) And (c>a) And (d<b))
ProcedureReturn 1
EndIf
If ((bit=0) And (bit_p=1) And (c<a) And (d>b))
ProcedureReturn 0
EndIf
If ((bit=0) And (bit_p=0) And (c<b) And (d>a))
ProcedureReturn 0
EndIf
ProcedureReturn #BAD_SAMPLE
EndProcedure
Procedure preamble(buf.a, i.i)
Protected i2.i
Protected low.a, high.a
low.a = 0
high.a = 255
; Returns 0/1 for preamble at index i
For i2 = 0 To #PREAMBLE_LEN-1
Select i2
Case 0,2,7,9
high = buffer(i+i2)
Default
low = buffer(i+i2)
EndSelect
If high <= low
ProcedureReturn 0
EndIf
Next i2
; Preamble sequence found
ProcedureReturn 1
EndProcedure
Procedure manchester(buf.a, len)
Protected a.a, b.a, bit.a
Protected i.i, i2.i, errors.i
a = 0
b = 0
i = 0
; Overwrites magnitude buffer with valid bits (#BADSAMPLE on errors)
While (i < len)
; Find preamble sequence
While i < len - #PREAMBLE_LEN
If preamble(@buffer.a(), i) = 0
i+1
Continue
EndIf
a = buffer(i)
b = buffer(i + 1)
For i2 = 0 To #PREAMBLE_LEN-1
buffer(i + i2) = #MESSAGEGO
Next i2
i= i+#PREAMBLE_LEN
Break
Wend
i2 = i
errors = 0
; Mark bits until encoding breaks
While (i < len)
bit = single_manchester(a, b, buffer(i), buffer(i + 1))
a = buffer(i)
b = buffer(i + 1)
If bit = #BAD_SAMPLE
errors+1
If errors > allowed_errors
buffer(i2) = #BAD_SAMPLE
Break
Else
If a>b
bit = 1
Else
bit = 0
EndIf
a = 0
b = 255
EndIf
EndIf
buffer(i) = #OVERWRITE
buffer(i + 1) = #OVERWRITE
buffer(i2) = bit
i+2
i2+1
Wend
Wend
EndProcedure
Procedure display(frame.a, len.i)
Protected i.i
Protected df.a, value.a, icao.a, pcode.a, tcode.a, stype.a
Protected test.b
If (short_output = 0) And (len <= #SHORT_FRAME)
ProcedureReturn
EndIf
df = (adsb_frame(0) >> 3) & $1F
If Quality=0 And Not ((df = 11) Or (df = 17) Or (df = 18) Or (df = 19))
ProcedureReturn
EndIf
Print("#")
For i = 0 To (Int(len + 7)/8)-1
Print(RSet(Hex(adsb_frame(i),#PB_Ascii),2,"0"))
Next i
PrintN("")
If verbose_output = 1
PrintN(FormatDate(" %yyyy/%mm/%mm/%dd %hh:%ii:%ss", Date()))
value=adsb_frame(0) & $07
PrintN(" DF="+df+ " CA="+value)
icao =(adsb_frame(1) << 16) | (adsb_frame(2) << 8) | adsb_frame(3)
PrintN(" ICAO= "+icao)
EndIf
If len <= #SHORT_FRAME
ProcedureReturn
EndIf
If verbose_output = 1
pcode=(adsb_frame(11) << 16) | (adsb_frame(12) << 8) | adsb_frame(13)
tcode=(adsb_frame(4) >> 3) & $1F
stype=adsb_frame(4) & $07
PrintN(" PI_code= "+pcode)
PrintN(" Type_code= "+tcode)
PrintN(" S_type/ant= "+stype)
EndIf
EndProcedure
Procedure outmessages(buf.a, len)
Protected.i i, index
Protected.a shift, frame_len, val_shift, data_i
i =0
lf_counter =0
sf_counter =0
While i< len
If buffer(i) > 1
i+1
Continue
EndIf
frame_len = #LONG_FRAME
data_i = 0
For index = 0 To 13
adsb_frame(index) = 0
Next index
While (i < len) And (buffer(i) <= 1) And (data_i < frame_len)
If buffer(i) = 1
index = Int(data_i / 8)
shift = 7 - (data_i % 8)
val_shift = 1 << shift
adsb_frame(index) = adsb_frame(index) | val_shift
EndIf
If data_i = 7
If adsb_frame(0) = 0
Break
EndIf
If adsb_frame(0) & $80 <> 0
frame_len = #LONG_FRAME
lf_counter+1
Else
frame_len = #SHORT_FRAME
sf_counter+1
EndIf
EndIf
i+1
data_i+1
Wend
If data_i < frame_len-1
i+1
Continue
EndIf
display(adsb_frame.a(), frame_len)
i+1
Wend
EndProcedure
Procedure.i demodulation()
lf_counter = 0
sf_counter = 0
length = magnitude(@buffer.a(), block_size)
manchester(@buffer.a(), length)
outmessages(@buffer.a(), length)
If show_stats=#True
PrintN("ADSB frames (Long/Short): "+Str(lf_counter)+"/"+Str(sf_counter))
EndIf
EndProcedure
Procedure ReadBufffer(*buf, len.l, *ctx)
If *ctx=0
ProcedureReturn 0
EndIf
; CopyMemory in Delphi (Destination: Pointer; Source: Pointer; Length: DWORD)
; CopyMemory in Purebasic (*Source, *Destination, Size)
CopyMemory(*buf, @buffer.a(), len.l)
; handle semaphore
hSem=CreateSemaphore()
MessageRequester("Info","Copy realized and semaphore created", 0)
ProcedureReturn 1
EndProcedure
Procedure ThreadProc(value)
Protected len.i
Protected WaitReturn.i
Repeat
;WaitReturn=WaitSemaphore(hSem)
;If WaitReturn=0
; CopyMemory (source, destination, taille)
CopyMemory(@buffer.a(), @thread_buf.a(), block_size)
len = magnitude(@thread_buf.a(), block_size)
manchester(@thread_buf.a(), len)
outmessages(@thread_buf.a(), len)
; FreeSemaphore(hSem)
;EndIf
ForEver
;rtlsdr_cancel_async(*dev)
EndProcedure
; ------- Main -------
pythagore_precompute()
OpenConsole()
If UseLibrtlsdr()
device_count = rtlsdr_get_device_count()
If Not device_count
PrintN("No supported devices found.")
End 1
EndIf
PrintN("Found " + Str(device_count) + " device(s)")
For i = 0 To device_count - 1
PrintN(" " + Str(i) + ": " + PeekS(rtlsdr_get_device_name(i), -1, #PB_UTF8))
Next i
PrintN("")
PrintN("Using device " + Str(dev_index) + ": " + PeekS(rtlsdr_get_device_name(dev_index), -1, #PB_UTF8))
r = rtlsdr_open(@*dev, dev_index)
If r < 0
PrintN("Failed to open rtlsdr device #" + Str(dev_index))
End 1
EndIf
PrintN("")
rtlsdr_set_center_freq(*dev, #ADSB_FREQ)
rtlsdr_set_sample_rate(*dev, #SDR_SRATE)
rtlsdr_set_tuner_gain(*dev, #SDR_GAIN)
rtlsdr_set_agc_mode(*dev, 1)
PrintN("Tuned to "+ rtlsdr_get_center_freq(*dev) + " Hz")
PrintN("Tuner gain: "+ rtlsdr_get_tuner_gain(*dev))
r = rtlsdr_reset_buffer(*dev)
If r < 0
PrintN("Failed to reset buffer")
EndIf
PrintN("Reading samples in Async mode")
PrintN("")
hThread=CreateThread(@ThreadProc(), 0)
MessageRequester("Info","ThreadProc running", 0)
r = rtlsdr_read_async(*dev, ReadBuffer, 0, 32, block_size)
If r < 0
PrintN("Buffer Async read failed\n")
EndIf
; Can't reach this point after rtlsdr_read_async
rtlsdr_close(*dev)
If r >= 0
End r
Else
End -r
EndIf
EndIf
CompilerIf #PB_Compiler_Debugger
Input()
CompilerEndIf
CloseConsole()
Thanks for your help, if possible.
