Hi Tom,
Thats the issue with the old Suntie's (pre V5.0 aka UPG), there is no Sync data you can use figure out where the stream starts, its totally timing based.
The UPG's DO have sync data, I added this when I did the redesign back in 2002, as the timing method is unreliable at best
As for the data, I posted on the Xantrex site a while back and didn't catch any flack, so I guess is not a state secret anymore
This thread should answer your questions
http://www.xantrex.com/forum/forum_posts.asp?TID=239&KW=STXR
The older STXR's do not report dc amps, mppt or power limit:
Here is the text from the Xantrex Post
First, it is important is to know the rs232 port is Not Isolated. You MUST use an external RS232 opto isolator or you will damage a PC if one is connected
The Suntie only reports data, there is no command interface, the receive line has no connection
A Free PC based program ( FishBowl ) is available at FishBowl For Suntie Download
As for the comm protocol, it's 9600 baud, no parity and the data is raw binary.
Any reported value greater than 256 is split into a high/low byte. A 34 byte data stream, once a second is sent out of the RS232 port
Here is most of the values of that 34 byte stream
Byte 0 fault
Byte 1 modes
Byte 2 Version
Byte 3 Mppthigh
Byte 4 VAChigh
Byte 5 VAClow
Byte 6 FREQhigh
Byte 7 FREQlow
Byte 8 AC_WATTShigh
Byte 9 AC_WATTSlow
Byte 10 FAULTTIMER
Byte 11 DC_VOLTS
Byte 12 DC_AMPS_Hi
Byte 13 mpptlo
Byte 14 DC_VOLTS_LO
Byte 15 DC_AMPS_LO
Byte 16 Power_Limit_Hi
Byte 17 Power_Limit_Lo
Byte 25 AmbientTemp;
Byte 26 HeatSinkTemp;
For syncing to the stream the last 5 characters sent out are "XR/GP" , when this is sent, the next character is the beginning if a new 34 byte stream