var
hport: thandle;
dcb: tdcb;
......

hPort := CreateFile(PChar('COM1'),
GENERIC_READ or GENERIC_WRITE,
0, nil,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if hPort = INVALID_HANDLE_VALUE then
begin
exit;
end;

if not GetCommState(hPort, dcb) then
begin
exit;
end;

dcb.BaudRate := CBR_4800;
dcb.ByteSize := 8;
dcb.Parity := NOPARITY;
dcb.StopBits := ONESTOPBIT;
DCB.Flags := 20625;

if not SetCommState(hPort, dcb) then
begin
exit;
end;

if not SetupComm(hPort, 8, 8) then
begin
exit;
end;

if not PurgeComm(hPort, PURGE_TXCLEAR or PURGE_RXCLEAR) then
begin
exit;
end;

if not SetCommMask(hPort, EV_RXCHAR) then
begin
exit;
end;

var
mmm: array [0..6] of byte;
....

//движение влево со средней скоростью

mmm[0]:= $FF;
mmm[1]:= $01;
mmm[2]:= $00;
mmm[3]:= $02;
mmm[4]:= $20;
mmm[5]:= $00;
mmm[6]:= mmm[1] + mmm[2] + mmm[3] + mmm[4] + mmm[5];


NumberOfBytesWritten := 0;

if not WriteFile(hPort, mmm, sizeof(mmm), NumberOfBytesWritten, nil) then
begin
exit;
end;