PicoShell — RP2350 SSH Terminal Cyberdeck

A pocket SSH terminal built on the Raspberry Pi Pico 2 W. Native 80-column color display via DVI, USB keyboard, WiFi SSH client. Under €50. Runs for 15+ hours on a LiPo.

Think: cyberdeck disguised as a modern GameBoy with too many keys.

Concept

USB Keyboard → Pico 2 W (RP2350) → WiFi → SSH → your servers
                    ↓
              HSTX DVI → 80x30 color terminal
              (core 1, no PIO needed)

Two-phase approach:

Phase 1 (thin client): Pico does keyboard + VT100 display. SSH runs on a Pi Zero 2W or any Linux box, connected via WiFi TCP. Also doubles as a serial terminal for headless boards.
Phase 2 (native SSH): wolfSSH client runs directly on the Pico. No companion needed. Full standalone operation.

Parts List

Part	Approx. Price	Link	Notes
Pimoroni Pico Plus 2 W	€15	Pimoroni	RP2350B, 8MB PSRAM, 16MB flash, WiFi/BT, USB-C
Adafruit PiCowbell DVI for Pico 2	€8	Adafruit	HSTX DVI breakout, no PIO needed
5“ 800×480 HDMI IPS panel	€20	Search AliExpress/Amazon for “5 inch HDMI LCD 800×480”	100×30 chars at 8×16 font. TFP401-based boards work well
USB OTG adapter	€2	Any USB-C OTG cable	For USB HID keyboard
SD card breakout (SPI)	€3	Adafruit or any SPI SD module	SSH keys, config, logs
3.7V LiPo 3000mAh + TP4056 charger	€5	AliExpress	~15h WiFi active, days in serial-only mode
Total	~€50

Key Technologies

HSTX DVI (RP2350 native)

The RP2350 has a dedicated high-speed serial transmitter (HSTX) that outputs DVI directly. No PIO state machines consumed, no overclocking needed.

640×480 @ 60Hz — 80×30 text with 8×16 font
800×600 @ 60Hz — 100×37 text
16-color text mode built into DispHSTX library (CGA palette, enough for xterm-16color: vim, htop, tmux)
256-color or 65K-color graphics modes for full xterm-256color rendering
Framebuffer in PSRAM (~300-480KB), SRAM stays free for SSH/networking
Library: DispHSTX (docs)

PSRAM on RP2350

8MB PSRAM on the Pimoroni board. Enough for framebuffer + scrollback + SSH buffers.

Use	Size
Framebuffer (800×600 8bpp)	480 KB
Scrollback (80×1000 lines + attributes)	240 KB
SSH buffers (wolfSSH)	100 KB
Heap / misc	~7 MB free

Gotchas (documented, workarounds exist):

Flash operations clobber PSRAM config — save/restore QMI registers (SDK issue)
Cache coherency bug on clean — use clean+invalidate (forum thread)
DMA to PSRAM is slow — double-buffer through SRAM (forum thread)
Analysis: Dmitry.GR RP2350 review

SSH on Pico

wolfSSH — lightweight SSHv2 library, client + server, ANSI C. GitHub
pico-sshd — SSH server running on Pico W, proves wolfSSH+lwIP works on this hardware. GitHub
wolfSSL crypto has explicit RP2350 support (incl. hardware TRNG)
Key exchange (RSA/ECDH): ~2-5 sec on Cortex-M33. Session crypto (AES-GCM/ChaCha20): fast.
No existing SSH client project on Pico — this would be a first.

Existing Projects / References

PicoTerm — VGA terminal emulator on Pico (serial, 80×30)
PicoCalc — ClockworkPi handheld ($75 kit, 320×320 display, QWERTY keyboard, 8MB PSRAM, but only 40 columns)
PicoDVI — DVI output for RP2040 (predecessor to HSTX approach)
pico-window — Text windowing system with FreeRTOS
pico-serial-to-wifi-bridge — UART↔TCP bridge for thin-client approach
PicoVision — Dual-RP2040 HDMI board (overkill but reference design)

vs Alternatives

	PicoShell	uConsole	PicoCalc
Price	~€50	~€200+	~€75
Wait	Next-day shipping	Months	Weeks
80 columns	Yes (DVI 640×480+)	Yes (Linux FB)	No (320×320)
Color	16/256 color	Full 24-bit	Mono/limited
SSH	wolfSSH / thin client	Native Linux	No WiFi in base
Battery	15+ hours	2-4 hours	Hours (2x 18650)
Weight	~100g	~300g	~200g
Hackability	Bare metal, full control	Linux, CM4	MicroPython/C
Display	External HDMI panel	Built-in 5”	Built-in 4“

Status

Phase: Planning. Repository: https://git.reauktion.de/marfrit/picoshell (once created).

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