Hey all
I'm new to SDR stuff, and am
trying to learn as much as I can. As hands-on practice is
best, I found a cheap and simple rf device to practice with.
Specifically,
this remote.
It transmits an (almost) static
signal, which can be replayed using hackrf_transfer. Each
button repeats the same signal, but with a counter which
increments as long as you hold the button down. Each button
transmits 12 bytes which include a preamble, sync word,
command, said weird counter, and a null byte to signal the end
of the transmission. As I understand, the data is fsk/nrz
encoded, but I've included a screenshot of the waveform I see
right after the Quadrature Demod block, so you can see what I
see. From the doc, the baud rate is 2400.
I'd like to create a software
version of the remote, which transmits the same signals as the
remote, but using GRC to encode the message properly. This is
where I'm stuck, so, I'm asking for help with two things:
1. How do you go about creating a
qt gui source block which outputs something that GRC can use?
What datatype should this block output?
2. How would I encode that output
in such a way that it would be identical to what the remote
transmits? I tried using the GFSK modulator with various
settings, but that didn't work, and I'm not sure why.
Regarding
what I've done so far: I created a receiver for the remote
in GRC. I used two custom blocks, so I've only attached a
screenshot of the graph in this mail. The Pattern Dump block
comes from here, and basically looks for a given
preamble, and passes the bits that follow to another block
as a message. I wrote the receiver block, which checks those
messages, and runs a different os command depending on what
button was pressed.
Thanks in advance for the help!