could you explain the 8 status bits, please? And the meaning of the last 3 digits?
T#529,083,002,036,035,071,10000000,000 ^^^^^^^^ ^^^
This is the standard APRS telemetry frame which can report up to 5 analog inputs, and 8 digital discretes.
In the original 1995 APRS Mic-E MIM module they were a fully independent 8 bit I/O port. Useful for discrete status bits. In the Kantronics 9612+ TNC, they are also a separate 8 bit I/O port (as used on PCSAT-1 and PCSAT-2) good for both inputs and commanding. But on the KPC-3+ TNC, they are mostly the same port as the analog telemetry pins.
We find these Kantronics TNC's to be very powerful. That is why we now have a total of 8 of them in space oas the primary command/control system for several satelites, and use another few dozen in out LAB satellites for the students to learn elements of satellite comms.
Actually the KPC-3+ has 8 A/D inputs, but only 2 are brought to the connectors. We bring out 3 more for a total of 5. But 3 are used internally and so that is why we only have 5 channels of telemetry. The first two bits are used for RS-232 handshaking inputs, DTR and RTS. On RAFT we actually use the DTR line (the first "1" above") as the SIGN bit for the battery current sensor. If it is 1, then the current into the battery is negative. In this case, 002 shows no input current from the sun, so the 036 current is out of the battery.
On ANDE, we use both the DTR and RTS pins as a 2 bit counter to indicate which of the four sets of telemetry are being transmitted. We call those the FRAME counter bits. So here is the definition of those 8 bits on any KPC-3+ TNC:
DR5I3210
Where D and R are the DTS and RTS inputs I is used internally? 5,3,2,1,0 are the 5 analong inputs which show in the telemetry frame as T#SSS,000,111,222,333,555
But we have always called them 1,2,3,4,5 in our documents for simplicity.
So in the 8 discrete bits, the "1"'s and "0"'s besides the first two and the internal one, are simply a binary reflection of the same 5 channels of telemetry as the actual 5 analog inputs. If they are above the digital threshold, they show as a "1" and if below the threshold, they show as a "0". Since the "I" pin is used internally (something to do with the optional real-time clock chip, it is not invovlved in the TELEMETRY command.
However, you can see it's value and might be able to still use it as a on/off discrete indicator I guess.
Anyway, with the inputs, and outputs, and password protected logon built into every TNC, we find them a powerful tool for all kinds of applications, not just APRS...
OH! And the last 3 digits on the end are a memory wash counter. We are looking for SEU hits on the RAM chip. All unused RAM is painted with a bit pattern, and periodically, the TNC checks for bit errors. It acumulates a total until the next reset. This was custom code we asked Kantronices to add for this mission to give us some "science" data. But there was never enough time to test it completely and we noticed on the ground that it would often jump to 999 on its own even on boot up. So we will probably ignore it...
Bob, WB4APR
Here is the RAFT tlm. I heard some packet signals but I only decoded one packet.
RAFT>BEACON,SGATE [21-Dec-06 14:49:40] <UI>: T#529,083,002,036,035,071,10000000,000
This is GOOD NEWS!
It shows that RAFT is now charged up enough to make it through eclipse. Notice that the telemetry serial number is up to
#529
which means it has now been running for 529 minutes since it last booted up. This is good news, because on the first few orbits, it was going to low-power shutdown towards the end of eclipse.
Thanks! Bob, WB4APR USNA Satellite Lab
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