Framework Laptop 16 Input Modules

This repository includes mechanical and electrical documentation for the Input Module system in the Framework Laptop 16. Input Modules are hot-swappable USB 2.0-interfaced devices that enable deep customization of the input system on the Framework Laptop 16. It's also possible to use these as standalone USB 2.0 devices with a simple adapter for development purposes.

Input Modules come in three sizes, each of which has the same electrical interface:

1. Keyboard-sized modules (283.16mm wide)
2. Numpad-sized modules (67.85mm wide)
3. Half-sized modules (33.825mm wide)

For reference firmware for different types of modules, check out these additional repositories:

• QMK firmware for the keyboard and numpad modules
• inputmodule-rs firmware and application for other input modules

Warning: the documentation here is pretty early, so there may be minor adjustments in the mechanical or electrical designs before the Framework Laptop 16 launches. We'll let you know when the design is locked for production.

License

Input Modules © 2023 by Framework Computer Inc is licensed under CC BY 4.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

Mechanical

In the Mechanical folder, we have 2D drawings of the different Input Module sizes. Note that there are two version of each:

1. A version with full mechanical structure with a separate interface PCB and brackets. This is what our production modules are based on.
2. A simplified version that allows the PCB to be used as the mechanical structure of the module, making it much cheaper and easier to make. Note that to make the PCB attach securely in the system, you'll need to solder SMT nuts like Keystone 24929 or to adhere a steel plate to attract to the magnets in the system.

Electrical

In the Electrical folder, we have a reference version of a minimal RP2040-based Input Module, made in KiCAD.

Pinout

Pin	Function	Note
1	GND
2	VCC_5V	5V, power supply from the system.
3	USB_DN	USB D-
4	BOARD_ID	Pull to GND through BOARD_ID resistor defined below
5	USB_DP	USB D+
6	SLEEP#	3.3V if the host is in S0. 0V if the host is in S0ix, S3, S4, S5
7	GND
8	VCC_3V3	3.3V, power supply from the system.

Viewed from top:

BOARD_ID values

Module Type	ID	Pulldown Resistor (on module)
Short	0	NA
Reserved	1	10000
Reserved	2	18000
Reserved	3	27000
Reserved	4	39000
Reserved	5	56000
Generic full width	6	68000
Reserved	7	82000
Generic keyboard size	8	120000
Generic medium size	9	150000
Generic small size	10	180000
Medium size keypad	11	270000
Keyboard	12	330000
Touchpad	13	560000
Reserved	14	820000
Not installed	15	NA

Power

Each Input Module supports up to 500mA on the 5V rail and 100mA on the 3.3V rail when active.

When SLEEP# is low or USB is in Selective Suspend mode, modules should drop below 500uA on each rail. This will typically occur when the system enters an S0ix state. In S3/S4/S5 or when the laptop lid is closed, the power rails will typically be off.

The Framework Laptop 16 has a protection scheme in place to prevent Input Modules from powering on unless the input deck is fully populated. Module detection is done using the BOARD_ID pin. It is possible to override this setting on the system, but at the risk of shorting the system or modules.

Touchpad Module

This section describes the Touchpad Module connection on the system side, including the pin define and the pin map of the connector.

Pins on the connector have ESD protection to meet IEC 61000-4-2 Level 4 protection.

Pin	Function	Note
1	GND
2	VCC_5V	5V, power supply from the system.
3	I2C_SCL	I2C Serial Clock Line
4	BOARD_ID	Pull to GND through BOARD_ID resistor defined below
5	I2C_SDA	I2C Serial Data Line
6	TP_INT_1	Secondary interrupt for touchpad future features
7	VCC_3V3	3.3V, power supply from the system.
8	TP_INT_0	Main interrupt for touchpad

Touchpad Module layout requirements

The contacts on the Touchpad should be designed so that the ground pins engage first when the Touchpad is sliding in. Pin 7 should be 0.5mm longer than the other pins to ensure it engages first.

The below picture for pads is shown in perspective. The view angle is on top of the PCB.

Around the signal pads there should be a ground fill keepout to prevent the pogo connectors from shorting the pads to ground or other signals when sliding in if the solder mask is scraped away.

Touchpad I2C Protocol

The I2C bus from the touchpad is connected to the CPU for HID over I2C and implements the Precision Touchpad Protocol.

It's also connected to the EC. This is used when booting without a touchpad. If the Windows driver tries to connect to an I2C device but finds it does not respond, it will disable that device. So we make the EC pretend to be the touchpad and send the same HID report descriptor as the touchpad would.