RTL-PSP

An RTL-SDR receiver for the Sony PSP. The PSP connects over WiFi to an rtl_tcp server on a PC, streams raw 8-bit I/Q, and renders a live spectrum + waterfall on the 480x272 screen. It also includes a mono WFM (broadcast FM) demodulator with audio out.

Tested in PPSSPP and on a PSP-2000 (ARK-5, 6.61, WPA2).

 RTL-SDR ──USB──▶ PC (rtl_tcp) ──WiFi/TCP──▶ PSP
                                              ├─ FFT ──▶ spectrum + waterfall
                                              └─ WFM demod ──▶ 44.1 kHz audio

Layout

Path	What
`psp/`	PSP homebrew client (C, pspdev SDK) → `psp/EBOOT.PBP`
`psp/src/net.c`	WiFi (sceNetApctl) bring-up and a small TCP client
`psp/src/rtltcp.c`	rtl_tcp protocol: header, tuning commands, I/Q stream
`psp/src/fft.c`	Float radix-2 complex FFT + Hann window
`psp/src/viewer.c`	Spectrum/waterfall rendering (oslib) and input
`psp/src/wfm.c`	FM discriminator, decimation, de-emphasis, resampler
`psp/src/demod.c`	Demodulator thread fed by an I/Q ring buffer
`psp/src/audio.c`	44.1 kHz mono output thread (stereo duplexed)
`psp/src/ui.c`	Settings screen and status messages
`tools/`	Build/install helpers

Build

The PSP client is built with the pspdev/pspdev Docker image:

tools/pspbuild.sh            # -> psp/EBOOT.PBP
tools/pspbuild.sh clean

Install to a real PSP (USB mode) or PPSSPP's memstick:

tools/install-psp.sh

Run

Start rtl_tcp on the PC (bind to all interfaces so the PSP can reach it):

rtl_tcp -a 0.0.0.0 -p 1234 -f 102500000 -s 250000

The PC firewall must allow inbound TCP 1234.

Copy EBOOT.PBP to ms0:/PSP/GAME/RTLPSP/ and launch it. On first run the settings screen asks for the server address; settings persist to ms0:/RTLPSP/config.txt.

Controls

Screen	Input	Action
Viewer	← / →	Tune ±100 kHz
Viewer	L / R	Tune ±1 MHz
Viewer	X	Toggle gain auto/manual
Viewer	Triangle	Toggle WFM audio
Viewer	Start	Pause / resume
Viewer	Select / Circle	Settings
Settings	↑ / ↓	Move field
Settings	← / → , L / R	Change value
Settings	X	Edit text / toggle
Settings	Start	Save and connect
Any	HOME	Quit

How it works

Tune — the client opens TCP 1234, reads the 12-byte RTL0 header, and sends set_frequency, set_sample_rate and gain commands.
Stream — rtl_tcp sends interleaved unsigned 8-bit I/Q. The client drains the socket into a ring and consumes the newest data.
Spectrum/waterfall — a 1024-point FFT of a Hann-windowed frame gives 1024 bins, FFT-shifted so the tuned frequency is centred. Magnitudes are mapped to a 256-entry palette; the waterfall is a scrolling 5650 image.
WFM audio — I/Q is decimated to ~256 kHz, run through a polar discriminator, low-passed by three cascaded boxcars (rejects the 19 kHz pilot and 38 kHz stereo subcarrier), de-emphasised (75 µs), and resampled to 44.1 kHz. The demodulator runs on its own thread so it never starves audio scheduling.

Status

Working

Live spectrum + waterfall from rtl_tcp in PPSSPP and on real hardware.
Mono WFM audio.
Settings persisted on the memory stick; live tuning while streaming.

Limitations

Bandwidth. The PSP's 802.11b link caps throughput at roughly 4 Mbit/s, so the sample rate must stay around 250 kSps. At 1.024 MSps rtl_tcp cannot keep up and drops samples. 250 kSps is enough for WFM but gives only a 250 kHz-wide waterfall.
Weak signals. Auto gain can settle low; use manual gain for weak stations.
Mono WFM only — no stereo decoding or RDS.

Gotchas worth remembering

ms0:/ maps to the memory stick root. Under PPSSPP that is ~/.config/ppsspp/ (so ms0:/RTLPSP/config.txt is ~/.config/ppsspp/RTLPSP/config.txt, not under PSP/).
Homebrew runs at 222 MHz unless it calls scePowerSetClockFrequency.
On the PSP, doubles are software-emulated and FPU divides are slow — keep the hot DSP path in single precision and avoid divides/modulo.
The demodulator's I/Q decimation and the audio boxcar cascade are what keep the 38 kHz stereo subcarrier from aliasing into the audio band; a single boxcar is not enough.
rtl_tcp serves one client at a time, and PPSSPP and a real PSP cannot share it simultaneously.
PPSSPP shares one emulated CPU across all threads, so a heavy DSP loop shows up as a low emulated frame rate and can overflow the audio queue.

License

MIT

rtl-psp