#!/usr/bin/env python
# coding: utf-8

# # Pulling radio data out of thin air
# 
# ## Yuval Adam

# ## Yuval Adam
# 
#  - Full stack developer and systems architecture consultant
#  - Using Python for **everything** for 10+ years
#  - https://yuv.al
#  - [@yuvadm](https://twitter.com/yuvadm)
# 
# 

# ## This talk
# 
#  - I never learned physics, RF engineering or signal processing
#  - But radios are pretty cool!
#  - Hopefully I can show you some neat things
#  - Slides and code @ https://github.com/yuvadm/radio-pyconil-2018

# ## Radio
# 
# ![static/waves.gif](static/waves.gif)

# ## Radio Waves
# 
# ![static/dipole.gif](static/dipole.gif)
# 
# *Source: https://en.wikipedia.org/wiki/Antenna_(radio)*
# 

# ## Hardware Radio
# 
# ![static/radio.jpg](static/radio.jpg)

# ## Hardware Radio
# 
# ![static/gsm.jpg](static/gsm.jpg)

# ## Software-Defined Radio
# 
# ![rtlsdr.jpg](static/rtlsdr.jpg)

# ## What's it good for
# 
#  - Digital TV broadcast ("Idan+", DVB-T)
#  - Airplane tracking (ADS-B)
#  - Weather satellites
#  - IoT project integration
#  - FM radio broadcast

# ## Airplane Location Tracking (ADSB)
# 
# ![static/adsb.png](static/adsb.png)

# ## Weather Satellites
# 
# ![static/noaa.jpg](static/noaa.jpg)

# ## Internet of Things
# 
# ![static/iot.jpg](static/iot.jpg)
# 
# *Source: https://blog.hackster.io/iot-devices-may-be-susceptible-to-replay-attacks-with-a-raspberry-pi-and-rtl-sdr-dongle-de6eca268fbf*

# # I/Q Sampling
# 
# ![static/cosample.png](static/cosample.png)
# 
# *Source: http://whiteboard.ping.se/SDR/IQ*

# ## I/Q Sampling
# 
# ![static/corkscrew.png](static/corkscrew.png)
# 
# *Source: http://whiteboard.ping.se/SDR/IQ*

# ## Modulations
# 
# ![static/amfm2.gif](static/amfm2.gif)
# 
# *Source: http://mriquestions.com/signal-squiggles.html*

# ## GQRX

# In[ ]:


# pyrtlsdr provides us bindings to work with the RTL-SDR driver

from rtlsdr import RtlSdr

sdr = RtlSdr()
sdr.sample_rate = 1.2e6       # 1,200,000 samples per second
sdr.center_freq = 91.8e6      # 91,800,000 Hz frequency for the radio station
sdr.gain = 'auto'             # tune the gain (AKA "volume") automatically

samples = sdr.read_samples(1.2e6 * 10)
sdr.close()


# In[1]:


# Alternatively, load previously captured samples from rtl_sdr
# and convert them from unsigned 8-bit samples to a complex IQ array

import numpy as np

raw = np.fromfile('/tmp/samples.in', np.uint8).astype(np.float64)
raw += -127
raw /= 2**7
samples = (raw[0::2] + 1j * raw[1::2]).astype(np.complex64)


# In[2]:


# We captured too many samples so we need to apply a low pass filter
# In other words, we have a too large window and we want to make it smaller

import scipy.signal as signal

BANDWIDTH = 200e3
DECIMATION_RATE = int(1.2e6 / BANDWIDTH)  # Decimation factor of 6

samples = signal.decimate(samples, DECIMATION_RATE)


# In[3]:


# Apply the Frequency DEmodulation
# We use something called a polar discriminator

samples = np.angle(samples[1:] * np.conj(samples[:-1]))


# In[4]:


# De-emphasis filter
# Even I'm not sure exactly how/why this works

# MAKE THINGS SOUND BETTER

d = BANDWIDTH * 75e-6
x = np.exp(-1/d)
b, a = [1-x], [1,-x]
samples = signal.lfilter(b, a, samples)


# In[5]:


# Decimate the signal down to something an audio driver can handle
# We only catch the mono part of the signal

AUDIO_RATE = 50e3
DECIMATION_RATE = int(BANDWIDTH / AUDIO_RATE)  # Decimation factor of 4

samples = signal.decimate(samples, DECIMATION_RATE)

# Amplify the signal volume
samples *= 10000
samples = samples.astype('int16')


# In[8]:


# HIT IT

import alsaaudio

device = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, device='default')
device.setchannels(1)
device.setrate(50000)
device.setformat(alsaaudio.PCM_FORMAT_S16_LE)
device.setperiodsize(120)

# Write data in chunks
for s in np.array_split(samples, 120):
    device.write(s)


# ## Review
# 
#  - Took a fixed set of samples, did some math on them
#  - Python, NumPy and SciPy are very good at doing fast processing of **static** data
#  - When handling **real-time** data, buffering becomes a serious issue
#   - How do you synchronize different input/ouput sample rates on the same flow?

# ## GNU Radio
# 
# - Comprehensive signal processing framework
# - Implemented many DSP primivites
# - Has a great scheduling engine
# - *Actually* generates flowgraphs in Python

# ## Where to go from here
# 
#  - Buy an RTL-SDR dongle, they start at less than $10
#   - eBay, AliExpress
#  - Learn more about SDR, signal processing
#   - https://osmocom.org/projects/sdr/wiki/rtl-sdr
#   - https://www.reddit.com/r/RTLSDR/wiki/index
#   - Michael Ossmann's video course - https://greatscottgadgets.com/sdr/
#  - But you don't really need do know math
#   - Lots of code is already written
#  - Explore the radio waves!

# ## Thank you! Questions?

# In[ ]: