Python ctypes. How to pass IN LPVOID to C++ function -

i trying use ctypes pass string c++ function, , 1 in return. function declaration is:

bool performaxcom_api _stdcall sendreceive(in handle phandle,                            in lpvoid wbuffer,                           in dword dwnumbytestowrite,                           in dword dwnumbytestoread,                           out lpvoid rbuffer) 

i happy enough handle , dword variables, , achieved out lpvoid in similar function following setup:

szreplybuffer = create_string_buffer(64) replybuffer = c_char_p(addressof(szreplybuffer)) 

which when used similar out lpvoid got string back.

my current method @ creating in lpvoid inputted string cmdstr (for example "e0=1") is:

szsendstr = c_char * 64 sendstr = szsendstr()  in range(len(cmdstr)):     sendstr[i] = cmdstr[i] 

i pass function using following declaration: status = sendreceive(byref(husbdevice), c_void_p(addressof(sendstr)), 64, 64, replybuffer)

i have tried lots of different permutations of passing sendstr function, never empty string in replybuffer. there way of passing string missing?

thanks

laurence