Posts Tagged HAM

Softrock application available

Here’s a compiled executable, including the rtl-sdr library, for those that don’t want to get the source on github and compile it.

Also, if anyone wants to design a logo, it would be much appreciated!


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Softshell pre-alpha

Softshell works!

Basic functionality of Softshell works!  In the image above, you can see the app (Cocoa-rtl-sdr is the old name) on the right.  I didn’t even have the text boxes wired in yet for the sample rate and center frequency, because I was so excited that it was working.  The samples from the receiver are transported into GNU radio over TCP where a simple FFT is being performed.  Notice that all the extra blocks needed for the original rtl-sdr aren’t needed, because I’m doing all of the uchar  to float conversion inside of Softshell.

The code that’s available on GitHub was hacked together with some network code that I can’t release right now, but I’m going to move it over to code that I can use soon.


Here’s a pre-compiled application for those that don’t feel like compiling it:


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Weird return value discrepancies between Softshell and RTL-SDR

I’ve made significant progress porting over the rtl-sdr code.  I added printfs to every function that interfaces with the USB port so that I can compare what happens.  Everything seems normal, up until the gainControl function.  Once there, the returns from my application are usually about one digit off of the rtl-sdr code.  If anyone has any ideas, I’d love to hear them!

Link to the comparison spreadsheet.

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Softshell, the MacOS RTL-SDR driver

For the uninitiated, a few months ago one of the developers in the V4L (video for linux)/DVB (digital video broadcasting) team,  Antti Palosaari, discovered that this cheap video tuner dongle could be used as a software defined radio.  Since then, it has developed a HUGE following!  The team over at osmocom helped to package the driver into a separate executable.  The application seems to work well, and even compiles on the mac.  The problem is, though, that you have to install the libusb library for it to work.  It’s not hard to do, but you have to install mac ports, then install libusb.  What a pain.

Most of the active discussion about rtlsdr appears to be happening at the RTLSDR subreddit.

RTL SDR compatible dongle

The idea behind Softshell is to port the osmocom rtl-sdr code into a native Cocoa application that doesn’t need libusb.  I’ve published the code to github, but it’s still very early in the development process.

This post is just meant as a heads-up for anyone with Objective-C experience and an interest.

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Spectrum analyzer development with ChipKit

Chipkit with 74595's connected to PLO2

Now that I know that trying to use the BusPirate with the 74595’s is basically a non-starter, I’ve moved on to using the ChipKit.  The ChipKit is a arduino-like board with a Microchip PIC32 micro controller.  The PIC32 is, as the name would imply, a 32 bit processor, running at 80 MHz.  That’s pretty impressive, if you ask me.  It has a boot loader and software package that makes it more or less compatible with arduino code.  I really like that I can just hack something together without all the setting up SFRs (Special Function Registers, or the bane of embedded device programmers existence).

Anyway, I’ve developed a simple “sketch” (program in arduino terminology) that accepts serial commands and executes SPI transfers using a set of pins through the 74595’s.  You can kinda see what’s happening in the logic analyzer trace above.  The top three traces are the SPI commands to the PLO module.  The middle two are the serial in and out of the chip kit.  The bottom three are the SPI commands to the 74595’s.  I had to zoom out far enough that you can’t see what the serial or bottom SPI contents are, but it’s basically “$,s,A,B,C,L,DDD…” where A, B, and C are the pins for SPI Chip Select, Clock and Data, L is the length of the transfer in bytes and DDD… is the contents of the transfer.  Currently, the limiting factor is the serial communication (by that I mean UART, not SPI), but I’m only using 9600 baud in this example.  The ChipKit uses an FT232R USB-Serial converter that is good into the megabaud.  In the future I’ll experiment with higher baud rates.

That’s basically, all.  I just wanted to post and say that it works.  By the way, the PLO module happily accepted its commands and tuned to 1024 MHz.  🙂

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