This is an interactive block diagram of the MNT Reform open hardware laptop. Click on a label in the diagram to jump to the corresponding bit of information.
For general information, visit the MNT Reform Website.
The default SOM of Reform.
The default SOC of Reform.
The four main 64-bit ARM cores of the default SOC of Reform. The bootloader and operating system usually run on these processors.
The additional 32-bit ARM CPU core of the default SOC of Reform. It is currently unused.
The GPU in the i.MX8M SOM. Official documentation is not public, but most of its functionality has been reverse engineered by the etnaviv project.
i.MX8M has a MIPI DSI block by Northwest Logic and a DSI PHY by Mixel. Both have open source drivers in the Linux kernel. Reform accepts MIPI DSI signal on the motherboard header J24. The DSI to eDP Converter converts the signal to eDP to drive the display panel.
i.MX8M has multiple SAI ports for digital audio. Reform uses only one of them, SAI2. It connects stereo output and mono input to/from the WM8960 DAC/ADC chip on the Reform motherboard.
I²C (Inter-Integrated Circuit) is a relatively low speed, 2-pin internal serial bus commonly used to connect chips with each other via addressed register reads and writes. In Reform, I²C is used in multiple places:
In the Keyboard: The Atmega32U4 controls the OLED display via I²C.
SPI, the Serial Peripheral Interface, is another digital interface for communication between two chips. In Reform, there is a yet to be used SPI connection between the SoC and the LPC.
PWM stands for Pulse Width Modulation. With the default SoC, PWM4 is used to drive the internal display’s backlight brightness.
Reform has physical slots on the motherboard for two mobile PCIe form factors: mPCIe and M.2 (also called NGFF) Key M. Each is connected to one of the two PCIe controllers of the SoC. Each controller has a single PCIe lane.
UART (Universal Asynchronous Receiver/Transmitter) is a type of serial port. In Reform, UARTs 1 and 2 of the default SoC are brought out to two 3-pin headers. UART1 (header J18, labelled SER2) exposes the default serial console. Connect a USB-UART cable from this header to another computer and set it to 115200 baud, 8N1. Then you can control the bootloader and see early kernel boot output.
The HDMI/DP block can encode and transfer framebuffers over HDMI or DisplayPort (muxed on the same signal lines). The driver has not yet been upstreamed by NXP and requires a signed non-ARM blob (Xtensa code) to be loaded into the HDMI/DP controller at boot. The vendor kernel driver can be hacked into a mainline kernel.
Reform has 3 external USB 3.0 ports and two internal USB 2.0 ports. All of these are derived from the two USB 2.0/3.0 root controllers in the SoC. One root controller (USB2) goes directly to the external USB port J17. The other controller, USB1 is split into the four remaining ports via the USB hub chip on the motherboard.
Reform uses both USDHC MMC/SD controllers of i.MX8M:
The second controller connects to the SD card slot on the motherboard via a level shifter. The level shifter converts between the SoC’s 1.8V and the SD card’s 3.3V signal levels.
The DDRC connects the physical LPDDR4 RAM chip to the blocks inside of the SOC, including CPU and GPU.
Ethernet in Reform is made from 3 parts (MAC, PHY and the connector with built-in magnetics). The MAC, which is a block in the SoC. In the case of i.MX8M, this is called FEC.
The PHY part of the Ethernet interface is a chip on the SOM. The default SOM has an Atheros AR8035 PHY, which is driven in Linux by a generic PHY driver.
Reform has a TI TUSB8041 USB Hub chip with four downstream ports, two of which lead to external USB3.0 connectors.
The Reform motherboard has a NXP PCF8523T realtime clock chip that is backed by a 3.3V lithium coin cell when the system is unpowered. It is accessed by the SoC via I²C.
The Reform motherboard has a TI SN65DSI86 (variant SN65DSI86IPAPQ1) chip that converts MIPI-DSI signals to eDP signals that the built-in display panel can understand. The DSI output on the default SOM is available on a flat cable connector. A short, 30 pin FPC cable goes from the SOM into the motherboard’s MIPI-DSI input connector directly below the SOM. The DSI signals are routed from there to the SN65DSI86 chip.
The eDP signals are available on the 2x15 pin, 2mm DuPont header J24. Normally, a cable is plugged into this header, routed through the right-hand screen hinge and it’s IPEX connector side plugged into the display panel.
The Audio DAC/ADC converts between the digital SAI audio signals and the signals on the audio jack and the speakers. It can drive both speakers and headphones with independent volumes.
The 3.5mm audio jack, also called a TRRS jack (Tip/Ring/Ring/Sleeve) can be used to connect headphones, an external power amplifier or a headset with integrated microphone.
The audio jack uses the CTIA standard to define which signals are located on which contacts on the plug:
Except for extreme undervoltage conditions (battery cells below 2.5V), the LPC is always running a C program that implements a state machine which watches over the battery cells and controls their charging and discharging/balancing.
In addition, the LPC can toggle the main power rails in the system on and off via GPIOs going to the relevant voltage converters and load switches.
The LPC can be directly controlled by Circle commands given via the keyboard.
Model: NXP LPC11U24
The barrel jack accepts DC voltage in the range of 7V to 32V. The default power supply shipped with MNT Reform is specified at 24V / 2A.
The following shortcuts are available indepdently of the main processor in Reform, even when the system is powered off. Acting like a primitive terminal, most shortcuts trigger a command string to be sent over the keyboard’s UART to the LPC. The LPC then responds with characters to display on the OLED.
In the 2.0D-3/D-4 development version:
Keep in mind that Circle + 0 powers off the system immediately, so save your work and make sure it is synced to disk before powering off. For example, use the sync or shutdown commands.
The keyboard and trackball modules both use the same type of switch.
The trackball has custom keycaps designed by MNT Research and 3D printed in an SLA process.
The OLED display sits on its own little PCB on top of the keyboard, and is powered and controlled by the keyboard’s MCU independently from the computer’s main processor.
The display is currently used to show the results of Circle commands given via the keyboard.
The display panel is connected to two main types of signals via a single IPEX connector:
PWM to set the LED backlight’s brightness. The brightness is set via the duty cycle of the PWM signal, while the frequency is set at a fixed value (default: 10KHz).
Reform uses 2x 8 Ohm, 1 Watt mobile speakers mounted below the display panel. They are powered by the Audio DAC.
Reform uses 8 battery cells with LiFePO4 (Lithium Iron Phosphate) chemistry.
The cells are connected in series, resulting in a 28.8V total voltage with high current capability. If shorted, traces can easily be burned and sparks could ignite nearby material. - Do not use metal tools or open wires inside of MNT Reform!