This is a prototype specification, not a finished product sheet. Rows marked Planned are changes we have decided on but not yet built — the journal covers why. Everything else is what is on the board in front of us.

PHYLAX PCB v3.1 held in one hand, showing the STM32F205RET6 microcontroller, the 8 MHz crystal, the display connector and the two tactile buttons — PCB v3.1. The MCU marking reads 32F205RET6; the display FPC connector sits above the Phi mark, the two buttons below it.

A multimeter reading 3.291 volts DC probed on the PHYLAX board next to the OLED panel — The 3.3 V rail, measured: 3.291 V out of the MCP1703 LDO.

Core

A general-purpose microcontroller running open firmware. There is no secure element, and that trade-off is explained in the FAQ.

Item	Specification
Microcontroller	`STM32F205RET6` — ARM Cortex-M3, 120 MHz, 1 MB Flash, 128 KB RAMPlanned: RET7 The RET7 is the automotive-grade part; we move to it if the temperature range justifies the cost.
Crystal	8.000 MHz `ABMM2-8.000MHZ-E2-T` for HSE, driving the 48 MHz USB clock through the PLL
Firmware	Stock Trezor Model One firmware, unmodified. We run upstream rather than a fork, so the code on the device is code that has already been audited and is verifiable against a published release.
Secure element	None. Keys are held on the microcontroller. See the FAQ for the honest version of what that costs you.

Display

The screen is where you verify an address before the device signs anything, so it is specified for legibility rather than for cost.

Item	Specification
Panel	2.42-inch OLED, `SSD1309` controller, 128 × 64, SPI interface
Logic supply	3.3 V direct
Panel supply	+12 V from an on-board `SX1308` boost converter
IREF	910 kΩ — approximately 10 µA nominal segment current

Power

There is no battery. The device draws power only while it is plugged in, so there is nothing inside with a shelf life.

Item	Specification
Input	USB VBUS, 5 V nominal
Protection	`MF-MSMF050-2` polyfuse (500 mA hold) and a `BAT60JFILM` Schottky for reverse blocking
3.3 V rail	`MCP1703AT-3302E` LDO, 250 mA — feeds the MCU and the display logic
12 V rail	`SX1308` boost, 10 µH inductor, `1N5819HW-7-F` diode, all-ceramic capacitorsPlanned: XAL4040-103MEC The moulded inductor replaces the bare wirewound part that was audibly singing.

USB

Wired only. No Bluetooth, no Wi-Fi, no NFC — this port is the entire surface through which the device can be reached.

Item	Specification
Connector	USB Type-C receptacle, `10178589-00011LF` — brings out only one data pair, so it works with the cable one way upPlanned: 16-pin A 16-pin part such as the GCT `USB4215` / `USB4216` carries both pairs and works in either orientation.
Interface	USB 2.0 Full Speed, 12 Mbps
ESD protection	`PRTR5V0U2X` on D+ and D−
Series resistors	22 Ω on D+ and D−
CC1 / CC2	5.1 kΩ pulldowns on each, for USB-C sink detection

User input and debug

Two buttons. Every transaction the device signs is one somebody physically confirmed.

Item	Specification
Buttons	2 × tactile switches, confirm and cancel — `SKHCBGA010` series, rated for 500,000 actuations
Programming	`TC2030` 6-pin SWD header
Licences	Firmware GPL v3 · hardware CERN OHL-S v2 · documentation CC BY 4.0