M2 Interface Definition¶

Scope¶

M2 defines a 75-position, M.2 E-key-style connector form. Positions 24–31 form the key, leaving 67 electrical contacts per connector. The workbook provides a base M2 allocation, a multimedia M2xM allocation, and M2xN/M2xA contact maps using the same 67-contact form.

• M2 — connected display, audio, storage, debug, and general embedded I/O.
• M2xM — multimedia display, camera, PDM, and I2S/PCM signals.
• M2xN — networking, USB, CAN, and UART signals.
• M2xA — motor control, analog acquisition, encoder, and timer signals.

M2xH and M2xP remain naming reservations; the workbook does not assign their contacts.

Connector convention¶

The pin numbers below use the workbook convention: odd-numbered contacts are on the top side and even-numbered contacts are on the bottom side, viewed from the card edge. Pins 24–31 are absent because of the E-key notch.

M2 base profile¶

M2 is the base profile for compact connected products. Its allocation is intended to cover a QSPI display and capacitive touch panel, Wi-Fi SDIO, 1-bit TF-card SDIO, analog audio, debug, USB, CAN, and general buses. Several contacts are intentionally multiplexed so that one module can select the function appropriate to its SoC and product configuration.

Color-coded M2 pinout guide¶

The colored bar is the table key. The two-sided contact table below is the authoritative M2 pinout, including alternate functions and multiplexing.

M2 contact assignment¶

This two-sided grid uses Bottom Pin / Top Pin / CN1 columns. The Alt columns record an additional multiplexed function when the workbook assigns one. Every function cell uses its category color from the legend above.

M2 pin descriptions¶

Grouped and colored consistently with the contact table above. The workbook does not define I/O directions; the direction column is therefore an integration aid that must be confirmed against the selected module and SoC documentation.

M2 sharing rules¶

• The workbook marks SWD as a multiplexed resource with two alternative routing options: the debug-UART positions (SWDIO on pin 43, SWCLK on pin 41) or the capacitive-touch I2C1 positions (SWDIO on pin 51, SWCLK on pin 49). Populate only one option per module and reserve a recovery strategy before reusing any of these contacts.
• SPI1 is shared with the 1-bit TF-card path; both are also exposed as the generic SDIO1_D0–D3/CMD/CLK controller bus, and pins 65/67 additionally carry CAN_TX/CAN_RX.
• The Wi-Fi SDIO2 data lines are also exposed as the generic SDIO2_D0–D3/CMD/CLK controller bus; several of the same contacts double as GPADC analog inputs.
• SPI2 and I2C3/I2C4 (pins 58–52) can alternatively carry PDM1/PDM2 digital-microphone signals, plus generic G0–G3/BUS0–BUS3 GPIO aliases.
• I2C2–UART3 share the same six positions (pins 38–34/39–35), which also carry generic G11–G16/BUS11–BUS16 GPIO aliases when not used for a named bus function.
• The QSPI display and capacitive-touch groups are separate at the signal level, but their power, reset, and wake behavior must be reviewed as one display subsystem.
• CAN_TX and CAN_RX are logic-level signals multiplexed onto pins 65/67, not separately allocated contacts. The carrier still needs a CAN transceiver and protection appropriate to the product bus.

M2xM multimedia profile¶

M2xM defines the multimedia connector allocation for display, camera, and digital-audio designs. It defines interface groups rather than asserting that every module can operate every group concurrently.

The workbook labels MIPI DSI and MIPI CSI as alternative signal maps. Those labels do not, by themselves, establish support on a particular μForge module or SoC package; confirm device capability and routing requirements in the selected module documentation.

M2xN networking profile¶

M2xN is the networking-oriented extension map. It assigns one 67-contact M2-form connector to Ethernet, dual USB, CAN, UART, reserved GPIO, and GND.

M2xA analog and motion-control profile¶

M2xA is the motor-control and acquisition extension map. It assigns one 67-contact M2-form connector to complementary PWM outputs, analog inputs, motor-driver control, Hall/encoder inputs, timer channels, reserved GPIO, and dedicated grounds.

Module declaration and implementation checklist¶

A module declaration should identify its base allocation and each supported extension map, for example M2, M2 + M2xM, or M2 + M2xN + M2xA. It should state the number of M2-form connectors implemented, their category, the implemented optional functions, and any mutually exclusive modes.

Before adopting this draft, verify:

• The M.2 E-key connector footprint, card outline, retention hardware, and insertion orientation.
• The number, placement, and category of M2-form connectors on the module and carrier.
• All multiplexed functions selected by the module, including any shared SDIO1/SDIO2, PDM, SWD (debug-UART vs. CTP I2C1), or CAN routing.
• Module-specific I/O voltage, current, reset, boot, and power-sequencing requirements.
• Whether a claimed M2xM MIPI, RGB, DVP, PDM, or I2S function is supported simultaneously or only as an alternate mode.
• Carrier-side requirements for CAN transceivers, USB protection, TF-card power/detect, display power, audio amplification, and external PHYs.