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nanoTX
TM
Telemetry Transmitter
60
Quasonix, Inc.
While this command incorporates the functionality of nine (9) or more commands, those commands are still usable.
For example, if the unit has the -VR option then the BT command can still be used by itself to switch between
TTL and RS-422 inputs for clock and data.
Examples:
IS ET
Sets unit to 'normal' mode expecting external TTL clock and data to be applied to the unit
inputs
IS PN15 4.5
Sets unit to internal clock/data with a PN15 pattern at 4.5Mbps
IS AT AUTO
Sets unit to use the auxiliary TTL input in clock free mode with auto bit rate enabled
IS EN 10
Sets unit to use the Ethernet interface for both clock and data and to set the desired bit
rate to 10 Mbps
4.2.1.1.3 Low Density Parity Check (LDPC) Command
– LD
The LD command enables, disables, and shows the current state of the Forward Error Correction (FEC) / Low
Density Parity Check (LDPC) encoder. There is an optional selection for the block and rate selection. This requires
purchase of the LD6 option which enables LD and enables user code selection. LD6 also allows the randomizer
command (RA or RN) to select CCSDS, if LDPC is enabled.
This is only valid in *PSK modes, and it automatically turns OFF differential encoding. When LDPC is disabled, the
state of DE is determined by the mode (eg. all *PSK modes default to DE On.)
If the transmitter includes the LD option (but not LD6)
, then LD 0 or LD 1 are used to disable or enable LDPC,
as shown in the example immediately following. With the LD option, the block size and code rate are always 4096
2/3.
Examples:
LD
Show the current encoder state
LD 1
Enable the LDPC encoder
LD 0
Disable the LDPC encoder
If the transmitter includes the LD6 option
, the user may select from the six implemented LDPC codes. This also
allows user selection of the CCSDS randomizer using the RA or RN command. Adding LD6 automatically enables
the existing LD option.
The IRIG standard calls out six variants of LDPC codes—all combinations of two different information block sizes
(k=4096 bits and k=1024 bits) and three different code rates (r=1/2, r=2/3, and r=4/5).
LD6 Code
Block Size and Code Rate
0
k=4096, r=1/2
1
k=1024, r=1/2
2
k=4096, r=2/3
3
k=1024, r=2/3
4
k=4096, r=4/5
5
k=1024, r=4/5