Looking for a Christmas present in 2018? Check out the Red Pitaya programmable hardware solution for your electronics lab or software defined radio. It’s amazing. 

Back in 2013, a bunch of Slovenian entrepreneurs set out to create the “Swiss army knife for engineers”. Red Pitaya came to market as a versatile solution for an electronics lab on a credit card sized module. Turns out that their ideas were right on the money.

Red Pitaya has followed in the footsteps of Arduino and Raspberry Pi as a versatile, reasonably priced tool for technicians and makers around the world. Similar to the Pi, most units are now sold as part of STEM^lab kits, which contain bundled applications and accessories.

My favorite is the STEM^lab 125-14 model which sells for US$310 or CDN$430. Designers leveraged the Zynq 7010 system on chip and added a variety of I/O connections. So, for your money, you get a powerful collection of programmable hardware which includes a dual core ARM Cortex A9 CPU, Xilinx FGPA, 512 MB RAM, Ethernet and USB. This all runs on a 5V 2 amp power supply. Oh, yes, and some Analog Devices ADC and DAC which run at 125 MHz sample rates and 14 bit conversion. Sound familiar?

Red Pitaya easily provides a dual channel SDR transceiver, but that was not its original intent. Original applications for the device were intended as an digital oscilloscope, signal generator and spectrum analyzer. Later, LCR meter and logic analyzer came along.

What has made Red Pitaya so successful? Two things. First, you can use it as a complete electronics test bench for under $400. Wow! Second is the global community and ecosystem which is providing a huge number of open source applications, including software defined radio.

So, what’s the ham connection? It turns out that Red Pitaya contains pretty much everything for homebrew SDR receivers and transceivers – embedded CPU, FPGA and ADC/DAC. More on that soon.

Red Pitaya Programmable Hardware – How it Works

Zinq provides the magic. The CPU runs embedded Linux. Both OS and applications are stored on a Class 10 micro SD card. The ARM Cortex A9 does three things. First, it runs as a controller and interface manager. Second, it loads bit streams into the FPGA, both at start-up and in real time – that’s the Red Pitaya programmable hardware part. Finally, it does additional data processing.

Red Pitaya provides its own Nginx web server. All applications run in a web browser which connects over Ethernet or WiFi. Writing applications is similar to Arduino except for two things. First is the FPGA programming, which can often be done by downloading open source libraries. Second is the partitioning between back and front end. Back end program segments run on the module. Basically they are traditional C++ or Python code running in Debian Ubunto. Front end program segments run in the browser and are written in HTLM5, CSS and Javascript.

Next, we will describe how Red Pitaya provides almost everything you need for a direct sampling SDR.