Here is some code that we use to scan for Garmin USB GPS devices. You
will have to adapt it to your purposes, but it should give you an idea
of the routines you need to use, and the order in which you need to use
them:
{ scan for USB devices }
deviceinfoset := SetupDiCreateDeviceInfoList(nil, 0);
if (DWORD(deviceinfoset) <> INVALID_HANDLE_VALUE) then
try
// Retrieve the device information set for the interface class.
guid := GUID_DEVINTERFACE_GRMNUSB;
aguid := @GUID_DEVINTERFACE_GRMNUSB;
newdeviceinfoset := SetupDiGetClassDevsEx(aguid, nil, 0,
DIGCF_PRESENT or DIGCF_DEVICEINTERFACE,
deviceinfoset, nil, nil);
if(DWORD(newdeviceinfoset) <> INVALID_HANDLE_VALUE) then
try
{ enumerate the devices }
aindex := 0;
while True do
begin
infodata.cbSize := SizeOf(TSPDevInfoData);
{ for each device }
if SetupDiEnumDeviceInfo(newdeviceinfoset, aindex, infodata) then
begin
pinfodata := @infodata;
bindex := 0;
while True do
begin
{ for each interface }
interfacedata.cbSize := SizeOf(TSPDeviceInterfaceData);
if SetupDiEnumDeviceInterfaces(newdeviceinfoset,
pinfodata, guid, bindex, interfacedata) then
begin
pinterfacedata := @interfacedata;
preqsize := @reqsize;
{ get the buffer size }
if (not
SetupDiGetDeviceInterfaceDetail(newdeviceinfoset, pinterfacedata, nil, 0,
preqsize, nil)) and (GetLastError =
ERROR_INSUFFICIENT_BUFFER) then
begin
{ allocate the buffer }
pdetaildata := AllocMem(reqsize);
pdetaildata.cbSize :=
SizeOf(TSPDeviceInterfaceDetailData);
{ get the details }
try
if SetupDiGetDeviceInterfaceDetail(newdeviceinfoset,
pinterfacedata, pdetaildata, Cardinal(reqsize),
preqsize, pinfodata) then
begin
{ check if the device has already been found }
apath := PChar(@pdetaildata.DevicePath);
alreadyfound := False;
for i := 0 to High(foundevices) do
begin
alreadyfound := foundevices[i].path = apath;
if alreadyfound then
begin
foundevices[i].found := True;
break;
end;
end;
if alreadyfound then
begin
Inc(bindex);
continue;
end;
{ add the device }
<snip>
finally
FreeMem(pdetaildata);
end;
end;
end
else
begin
anerror := GetLastError;
if anerror = ERROR_NO_MORE_ITEMS then
break;
end;
Inc(bindex);
end;
end
else
begin
anerror := GetLastError;
if anerror = ERROR_NO_MORE_ITEMS then
break;
end;
Inc(aindex);
end;
finally
SetupDiDestroyDeviceInfoList(newdeviceinfoset);
end;
finally
SetupDiDestroyDeviceInfoList(deviceinfoset);
end;
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