The Raspberry Pi Pico is becoming the Swiss Army Knife of microcontrollers, and this is largely down to the flexibility provided by the programmable IO (PIO) and the $4 price tag. In the latest project to grab our attention, we see Luigi Cruz, a computer student and amateur radio enthusiast, use the Pico as a software defined radio (SDR) interface for the popular GNR Radio application.
Cruz's SDR project, PiccoloSDR, uses one of the analog input pins to sample 8 bit data at 500ksps. Cruz has connected the Pico's analog input to the output of his soundcard and uses an online tool to generate tones that are visible on his computer. To connect the Pico to the computer, Cruz explains, "The data is sent via USB using the RNDIS protocol to emulate a TCP/IP interface. The ADC speed is limited to 500 ksps. The data can be used with software like the GNU Radio with a custom block." This provides a low-bandwidth means to get data from the Pico and into applications such as GNU Radio.
Cruz continues the demo by showing how you can use the GNU Radio to view and analyze the audio input; for example, Cruz plays a video file, and we can see the audio frequency and sample rate in GNU Radio.
It is still early days for PiccoloSDR, but we can see a Raspberry Pi Pico powered scope for basic electronics work. Right now, there is no public code with which we can replicate this project, but it is only a matter of time until Cruz announces the details via his Twitter account.