Differences

This shows you the differences between two versions of the page.

--- megacode [2014/12/28 19:47] – [protocol] kingkevin
+++ megacode [2014/12/28 20:08] – [sdr] kingkevin
@@ Line 1: / Line 1: @@
 The [[http://www.linearcorp.com/|Linear]] [[http://www.linearcorp.com/radio_control.php|remote control]] solution from the [[http://www.linearcorp.com/radio_control.php#megacode|MegaCode series]] was used in the facility complex I was living for a short while, and I wanted to know how secure it is. Thus I reverse engineered it.
-===== transmitter =====
+In [[https://www.cuvoodoo.info/?post_type=podcast&p=69|episode #004]] I presented how the transmitting part works, and how to clone the radio remote controls. In [[https://www.cuvoodoo.info/?post_type=podcast&p=41|episode #005]] I presented how the receiving part works, so to record codes and analyze them.
-In [[https://www.cuvoodoo.info/?post_type=podcast&p=69|episode #004]] I presented how the transmitting part works, and how to clone the radio remote controls.
+===== transmitter =====
 ==== ACT-34B ====
@@ Line 42: / Line 42: @@
 The PICkit2 programmer does support the PIC12F family because it's flash based.
 But code and data protection were.
-===== receiver =====
-In [[https://www.cuvoodoo.info/?post_type=podcast&p=41|episode #005]] I presented how the receiving part works, so to record codes and analyze them.
+===== receiver =====
 ==== MDR ====
@@ Line 101: / Line 100: @@
 The first bit frame is used as sync frame and is always a 1.
 It is followed by 20 system code bits and 3 data bits.
+===== software defined radio =====
+This signal can be recorded using a software defined radio (SDR).
+I used the inexpensive USB DVB stick [[https://sdr.osmocom.org/trac/wiki/rtl-sdr|RTL-SDR]].
+First find the exact frequency at which the remote transmits using an FFT software, such as [[https://sdr.osmocom.org/trac/wiki/sdrangelove|sdrangelove]].
+Use this frequency to record and demodulate the signal using [[https://sdr.osmocom.org/trac/wiki/rtl-sdr|rtl_fm]]:
+<code>
+rtl_fm -f 317.962M -M am megacode.pcm
+</code>
+The recorded data can be view in audio editing tools such as [[http://audacity.sourceforge.net/|audacity]] by importing it as raw data, 24kHz, mono, 16 bits little endian.
+The code can also be extracted using [[https://git.cuvoodoo.info/kingkevin/megacode/blob/master/sdr/decode.rb|decode.rb]]
+<code>
+./decode.rb megacode.pcm
+</code>
+This decodes the transmissions and lists the 3 bytes values.
+<code>
+# egdes: 0
+# pulses: 0
+# groups: 1 (1)
+# transmissions: 0
+# values: 0
+# egdes: 1822
+# pulses: 167
+# groups: 9 (24, 24, 23, 13, 10, 24, 24, 24, 1)
+# transmissions: 5
+# values: 5
+values:
+- value: 13178818 (0xc917c2), system code: 598776 (0x922f8), databits: 2 (0x2)
+- value: 13178818 (0xc917c2), system code: 598776 (0x922f8), databits: 2 (0x2)
+- value: 13178818 (0xc917c2), system code: 598776 (0x922f8), databits: 2 (0x2)
+- value: 13178818 (0xc917c2), system code: 598776 (0x922f8), databits: 2 (0x2)
+- value: 13178818 (0xc917c2), system code: 598776 (0x922f8), databits: 2 (0x2)
+</code>