piRadio Portable - piRadio2
After a lot of development, I've finally completed the portable piRadio, an RTL8192-based SDR radio that runs either as a server or in standalone mode.
In server mode it behaves as one would expect, running rtl_tcp streaming data packets over the network. The on-board LCD display will indicate the assigned IP address making for simple connections from your PC-based software such as GQRX (OSX) or HD SDR etc. The switch on the right can be used to select the mode and it is read at boot up.
In standalone mode, the software running natively on the Raspberry Pi displays a realtime spectrum scope. In addition, when the rotary control is pushed, a menu is displayed allowing one to choose the modulation mode, the step size and the gain.
The software is based on rtl_fm and kiss_fft and highly optimized to run on the Raspberry Pi's limited resources. The kernel is customized to support SPI LCDs.
The hardware also includes the Ham-it-up RF up converter. Without this the RTL8192 dongle wouldn't be able to receive below 50MHz however with the onboard crystal on the up-converter, HF is receivable from 125MHz onwards. The up-converter can be enabled by selecting the second from the left switch and doing so automatically incorporates the offset adjustment for the display (or shows that an offset should be applied in the case of the server mode).
Two 5300mAH lithium ion batteries and an on-board charger / boost circuit power the Raspberry Pi for hours.
I plan to incorporate RTTY, AIS and ACARS decoding into future software builds. If there is enough interest I'll release the schematics and source code.