SOLVED Serial Comm With Security Panel

i have ademco vista-15p alarm system control panel , keypad:
panel's wiring diagram: http://www.home-security-systems-answers.com/images/ademco-vista-20p-007.jpg
what looks like: http://imagehost.calabro.us/images/ademco1.jpg

i "tap" serial communications board uses talk keypad can use arduino (jeenode) monitor. according this thread security panel uses serial interface rs-232  4800, 8, e, 2.

in past i've used attached circuit establish serial comm between raspberry pi , arduino, logic shifter. can use same circuit interface security panel? or need rs-232 shield?

(i've tried proposed logic shifter circuit didn't out of it, try debug more i'd know if i'm wasting time approach)

code snippit i'm trying use establish comms (from other thread posted above):

code: [select]


// open serial communications:
// alarm panel uses 4800, 8, e, 2; i'll go 4800, 8, e, 1
// because serial port treat stop bit an
// inter-character gap
void setup() {
 serial.begin(4800, serial_8e1);
}

void readalarmdata() {
 static int count = 0;
 static int state = 0;
 static char input_string[alarm_str_len+1] = "";
 
 while (serial.available() ) {
   // new byte:
   char inchar = (char)serial.read() & 0x7f;


logic shifter uses mps2222a transistor

pi , arduino both use ttl level on pins.on pi of pins 3.3v
since alarm system uses rs232 means voltage signals not 5v compatible, in order listen "tx" line of alarm system need rs232/ttl converter.
a way "see" bytes of communication using pc software realterm , set baud , watch passed on tx wire connecting rx pin of rs232/ttl converter
this give clear picture of alarm system protocol
then move arduino programing
ps:looking picture think alarm uses rs485 not rs232 since rs232 small distances , not allow wire shared.since devices have addresses should rs485.check it...

Arduino Forum > Using Arduino > Networking, Protocols, and Devices (Moderator: fabioc84) > SOLVED Serial Comm With Security Panel

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