Could I ask for some help and advise on this issue.
I am trying to interface my Microchip Pic based sim hardware to FG. I have
it working with a genetic string but the string is becoming to large for the
pics to handle, also I would like a crc or check sum on the data. Thus i
prefer a compressed hex format. Ie the pic sends 4 bytes sync,16 bytes each
bit being a switch boolean, 16 bytes each being an analog setting then 2
bytes with each bit being a sign on the 16 analogs.
The format thus is A5 5A A5 5A hh hh hh hh hh hh .......for 40 bytes.
For simplicity I opted to clone and adapt the Atlas driver, keeping in line
with all existing FG conventions. and use it as a frame. and intigrate my
driver into FG when i build.
So far I have bumbled my way along, I not a good programmer but have learnt
my way around C with the microchip C18 to drive all the hardware. I have
managed to generate and output a binary compressed message from FG. But cant
seem to get it to decode on the inwards stream.
My approach is similar to the way i run the can bus between the hardware
Pics, pick up the char one at a time, check for the first A5, then 3 sync
chars from "buf" then if ok (synced up), copy the next 40 chars to "msgin".
If thats ok then it sets a flag to decode the data. for now i also have an
0x0D on the end making it 41 chars. Later i intend to add the CRC routine.
Also I intend to use a network socket to the Pics once its all working. I
try to work in small steps.
It seems I cant pick up the first A5, as I understand it, "buf" has the data
in.
My question is how does the low level IO in Sg and FG work, am I wrong to
work on the premise that every time parse message is called buf contains
fresh data from the serial, Or does the the low level code require a CR? DO
i need to set up a static ring buffer os sorts and take the incoming from
that?
Below Is the code as it stands. i would expect to come out of this with
Msg_CS_OK=1, but maybe its not quite correct, for starters I need to pick up
the first sync char.
I hope i have provided enough info to enable an answer,
Regards Harry
FYI the OS is suse11.1 but i am not having any problems from that point of
view.
bool FGSim::parse_message() {
SG_LOG( SG_IO, SG_INFO, "parse atlas message" );
char msgin[256],dblin[6];
char a,b,c,d,e,f,g,h,b0,b1,b2,b3,b4,b5,b6,b7,w,starter,Char_Count,ch,l;
static char Msg_State,Msg_pointer,Message_CS_H,Message_CS_L,Msg_CS_OK;
double min, max;
int intin;
char pbsw;
// string msg = buf;
// msg = msg.substr( 0, length );
// SG_LOG( SG_IO, SG_INFO, "entire message = " << msg );
SGPropertyNode * node;
Char_Count = 41; // length
l =0;
while(l != Char_Count)
{
ch = buf[l];
switch (Msg_State)
{
case 0: // find the sync header byte 0
if(ch == 0xA5)
{
Msg_State++;
Msg_CS_OK = 0;
b5=false; // test
to see if value recieved.
node = fgGetNode("/controls", true);
node->setBoolValue("gear/gear-down", b5);
}
break;
case 1: // find the sync header byte 1
if(ch == 0x5A) {Msg_State++;}
else Msg_State= 0;
break;
case 2: // find the sync header byte2
if(ch == 0xA5) {Msg_State++;}
else Msg_State= 0;
break;
case 3: // find the sync header byte 3
if(ch == 0x5A) {Msg_State++;Msg_pointer=0;} // reset
counter point for msgin
else Msg_State= 0;
break;
case 4:
msgin[Msg_pointer] =ch;
Msg_pointer++; // write ch to msgin till all done
if(Msg_pointer==40){Msg_State++;Msg_CS_OK=1;}
break;
case 5: // get fist cs byte
Message_CS_H = ch;
Msg_State++;
break;
case 6:
Message_CS_L =ch;
Msg_State = 0;
break;
default:
Msg_State=0;
break;
} // switch
l++;
} // while
.....
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