Item |
Model |
approx.
Price |
LNB |
No-Name, NF 0.5 dB |
15 EUR |
Set-Top
Box |
Palcom DSL-380 |
35 EUR |
Analog Comparator |
Analog Devices AD8561AN |
5 EUR |
Microcontroller / Board |
Atmel AT91SAM7X256 / Olimex
SAM7-EX256 |
100 EUR |
Objective |
Solution |
Side
Effects |
Tap into tuner output. |
A slot was cut into the
back side of the box, and a tree-pin socket was glued with epoxy onto
the tuner. The three pins were conected to I+, GND, and I- (or Q+, GND,
Q-). |
Box looks more fancy. |
Disable main processor
after it has configured the tuner. |
A switch was connected to
the reset pin of the JTAG interface on the main PCB. After start-up,
the switch is used to hold the main processor permanently in reset. The
switch was mounted using the hole for the optical audio out socket,
wheich was removed. |
1. Power supply to the LNB
is switched off. 2. The analog gain control input to the tuner is switched off (very low gain). 3. Box looks even more fancy. |
Supply power to the LNB
permanently. |
Unsolder transistor Q3.
This transistor is used in the network that controls the 14 V / 18 V
power supply regulator. Removing Q3 lets the control voltage go high
permanently because of a pull-up resistor. |
none |
Generate a suitable gain
control signal for the tuner. |
A 100 kOhm trim pot was
connected to +5V via a 2.2 kOhm resistor, and to ground at the other
end. The centre pin is conected to the gain control inpot of the tuner.
The trim pot now allows to adjust the gain. |
none |
Firmware-20090107.tgz |
Tarball
with sources for AT91SAM7X firmware, including compiled
output (in binary and S-Record formats). Compilation requires ARM cross
compiler (arm-elf-gcc). |
udp_rx.c | UDP receiver software. Compile
like this:cc -Wall -O3 udp_rx.c -o udp_rx |
testract.c |
Utility for entropy
extraction using AES, with on-line test of input data. Compile like
this:cc -Wall -O3 testract.c -o testract -lm -lssl |
udp_rx
writes raw data
to standard output, and that testract
pipes
from standard input to standard output.
udp_rx >sample_raw.bin
udp_rx | dd bs=1024 count=20480 of=sample_raw.bin
testract
utility
checks the quality of input on-line data by calculating the byte
entropy for each input block of 4096 bytes. It aborts when the
calculated entropy is below a threshold given on the command line (2nd
argument). Note that the byte entropy is somewhat underestimated due to
the small sample size of 4096 bytes. The
data are compressed using AES as described above. The number of bytes
taken from each AES output block is also specified on the command line
(1st argument).
testract 12 7.8 <sample_raw.bin >sample_cooked.bin
udp_rx | testract 12 7.8 | dd bs=1024 count=1048576 of=cooked.bin
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 466.669 secs (2300863 bytes/sec)
sample_raw.bin |
20 MB |
raw data, generated as described
above |
sample_cooked.bin |
16 MB |
data of sample_raw.bin after
piping through testract 12 7.8 |