Skip to main content
Join the official 2020 Python Developers SurveyStart the survey!

Spectrogram (80MHz bandwidth) accelerator for LimeSDR

Project description

# 80MHz bandwidth with LimeSDR-Mini and GQRX [![Build Status](https://travis-ci.org/gasparka/spectrogram.svg?branch=master)](https://travis-ci.org/gasparka/spectrogram)

![Bluetooth GIF](https://github.com/gasparka/spectrogram/blob/master/doc/demo.gif “Demo”)

[LimeSDR-Mini](https://www.crowdsupply.com/lime-micro/limesdr-mini) diagram:

![Block diagram](https://github.com/gasparka/spectrogram/blob/master/doc/lime_and_diagram.jpg “Diagram”)

_**Note:** DC-removal is based on [Linear-phase DC Removal Filter](https://www.dsprelated.com/showarticle/58.php) (Dual-MA 1024 taps)_

## Install

Install the helper script to bootstrap the Docker images (Linux PC/ARM architectures):

`pip install spectrogram`

_**Rasbian note:** Use `pip3`. Executable is installed to `/home/pi/.local/bin/spectrogram`, which is not on PATH by default._

_**Ubuntu 20 note:** Does not work! Use 18 :)_

## Usage

Invoking `spectrogram` does following: 1. If needed, programs the LimeSDR-Mini with FPGA accelerator ( restore with spectogram --fpga_restore) 2. Starts the local ‘SoapySDR-Remote’ server 3. Starts GQRX

_**Warning:** You should cool your LimeSDR-Mini, especially the FPGA. It takes 2.5 minutes for FPGA temperature to rise from 30C to 80C, after which you risk damage!_

Works on RaspberryPi:

![Pi setup](https://github.com/gasparka/spectrogram/blob/master/doc/lime_mini_screen.jpg “lime_mini_screen”)

_**Notes:** Current draw was around 1.25A@5V. 5’ TFT-Display created some noise in the spectrogram - this was not a problem with HDMI display. OTOH HDMI supports higher resolution, which may cap the CPU if GQRX window is too big (updating the waterfall is expensive)._

### Remote usage

Pair your LimeSDR-Mini with RaspberryPi and execute `spectrogram --server_only` - this sets up a SoapySDR-Remote server. Next, on the monitoring device, execute `spectrogram` - this scans for remote devices and opens GQRX if one is found. Network bandwidth will be around 1 MB/s.

## MISC

### Using without GQRX [See demo notebook](https://github.com/gasparka/spectrogram/blob/master/doc/usage_demo.ipynb)

### Accuracy vs floating-point model

This is a fixed-point accelerator, accuracy against the floating-point model has been verified.

![fix vs float accuracy](https://github.com/gasparka/spectrogram/blob/master/doc/fix_vs_float.png)

[Reproduce](https://github.com/gasparka/pyha/blob/develop/pyha/applications/spectrogram_limesdr/spectrogram_limesdr.ipynb)

### How is 512 point FFT comparable to 131k FFT?? It’s about how many samples are averaged e.g. the 131k FFT averages 131k samples - same can be achieved with 512 point FFT and averaging 256 results - 512*256 = 131k.

![132k FFT vs 512 + averaging](https://github.com/gasparka/spectrogram/blob/master/doc/131k_vs_512.png) [Reproduce](https://github.com/gasparka/spectrogram/blob/master/doc/131k_vs_512.ipynb)

In general this is a trade-off - hardware complexity is reduced, but you will lose ~3dB dynamic range.

### Cooling solutions

#### No cooling

![No cooling](https://github.com/gasparka/spectrogram/blob/master/doc/no_cools.JPG)

Took 5 minutes to go from cold to critical FPGA temperature.

You will risk damaging your board!

#### Heat-sink on FPGA

![FPGA sinked](https://github.com/gasparka/spectrogram/blob/master/doc/fpga_cools.JPG)

Temperature is stable at ~65C after 10 minutes.

#### Heat-sink everything

![Massive sink](https://github.com/gasparka/spectrogram/blob/master/doc/all_cools.JPG)

Temperature is stable at ~54C after 20 minutes.

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for spectrogram, version 1.0.9
Filename, size File type Python version Upload date Hashes
Filename, size spectrogram-1.0.9.tar.gz (4.5 kB) File type Source Python version None Upload date Hashes View

Supported by

Pingdom Pingdom Monitoring Google Google Object Storage and Download Analytics Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page