MNT Reform Pocket

DIY Kit
The assembly process was fast and smooth.
Main issues were related to flex connectors... I am never sure if they are fully seated or not.
I have misplaced the antenna stickers to the bottom of the back panel... but not a big problem, Wi-Fi and BT works fine. I needed to tape the cables a bit and make sure screen flexi was not touching antenna cables.
I had to reseat  screen flexi as backlight was not stable.
The trackball ball was defective, but I used a bit of "super glue" to fix it up.
Overall it is ingenious design (e.g. use of PCB for panels and slot covers) and very high quality make. SLA prints are super nice.
 

Issues
No sound output on headphones
Use 
alsamixer and F6 to select sound card. Mess with mutting/unmutting controls there.
I was expecting the "stereo" output Pipewiere is for headphones but that is not the case. Both speaker and headphones outputs work as the same output, just headphones are muted by default on ALSA level.
Notch in the trackball
My trackball had a little notch making it stick. A bit of "super glue" and sandpaper did the trick.
On first boot screen is blank or only top half of it is working and looks corrupted
Just boot again. Looks like some initialization issue.
Screen backlight unstable
Reseat screen flexi cables. Move them away from Wi-Fi antenna cables. I used sticky tape to tape the Wi-Fi antenna cables to cover PCB and taped the screen cable so it takes less space.
SSD not showing up
Apparently not all SSDs work with this hardware. I guess some my have too much power drain at startup.
One that is not working: Samsung 980 Pro
I found working drive: SK hynix BC711 256GB M2. 2230
It needs M.2 2230 extension like this one to install: 2230 to 2280 m.2 adapter ssd.

Internals
Power
STANDBY_3V3 - Always on (manual switch), supplied from MAX1837EUT33 regulartor (VCC 5V -> 3.3V)
system MCU
VCC
USB port
I2C pullup
Reset pullup
RTC
FUSB302BMPX (USB-C with power delivery)
Qwiic I2C
Power rails latch (enables other power domains)
SYSCTL UART 1 connector (keyboard)
W25Q32JVSS (Flash?)
VCC 5V - Supplied from charcher
MAX1837EUT33 (4.5V - 24V -> 3.3V) provides STANDBY_3V3
TPS5450DDAR when enabled via power latch provides 5V rail
TPS5450DDAR when enabled via power latch provides 3.3V rail
LM2830XQMFE/NOPB when enabled via power latch profides 1.1V rail
USB_VBUS - Power form USB-C port 1 (PD port)
VCHG Power to charger
+5V - Enabled via latch
AP22815A Power distribution switch; when enabled it powers USB_VBUS so any connected USB device for port 1 (PD port)
TLV320AIC3100 Audio codec for speaker and headphones
USB port 2 VBUS
TPD12S521 HDMI port
SoM (CPU card)
TUSB8041 USB Hub
Keyboard USB power
(not connected) Internal USB port for flashing SYS MCU (Receptacle) - this is via do not populate (DNP) resistor so it is not connected to +5V
+3V3 - Enabled via latch
TXS0108EPW level shifter for modem (+1V8 -> +3V3)
MicroSD card slot
TPD12S521 HDMI port
IMX Reset pullup
DAC I2C pullup (audio)
IMX Uart pullup
NCV1117ST18T3G 3.3V -> 1.8V (1V8 supply)
Ethernet LED
USB Hub
M2 connectors
M2 phone modem
MIPI-DSI Display connector
+1V1 - Enabled via latch
USBH_1V1 USB Hub
+1V8 - Powered from +3V3 rail by TLV1117-18 (or ON SEMI NCV1117ST18T3G)
MIPI-DSI Dispaly connector
TXS0108EPW level shifter for modem (+1V8 -> +3V3)
MicroSD card slot
TLV320AIC3100 Audio codec for speaker and headphones
Summary:
Main power from batteries/charger or USB-C comes on VCC 5V.
Standby 3.3V power is regulated from the VCC 5V and is supplied to many components including charger (not used), system MCU, keyboard MCU (via UART connector), power latch, real time clock, USB-C PD chip.
Power latch is used to enable other rails: 5V, 3.3V (both regulate VCC 5V) and 1.1V (from 3.3V).
The 5V power is used many chips, USB power, SoM power, internal USB to keyboard.
The 3.3V power may chips and is used for SoM UART and I2C audio chip pullups.
The 1.1V is used only for USB Hub.
There is also 1.8V supply that regulates from 3.3V for display, modem, MicroSD card and audio.
Interfaces
Qwiic
Internal connector
Powered with 3.3 standby power
I2C to the SYS MCU (SDA0/GPIO0, SCL0/GPIO1)
Pinout:
GND
3.3V (standby)
SDA (RP2040 SDA0/GPIO0)
SCL (RP2040 SCL0/GPIO1)
On SDA0/SCL0 we also have two chips on charger board and PD chip FUSB302BMPX.
SoM Serial Connector
Documentation
They both go to the SoM card and depending on the type of card used they can be used to access boot output.
Connector J16 - 6 pins sticking out between SYSCTL and speaker connectors
3.3V
Pins left to right; assuming that the ports of the motherboard are on the right:
S2 GND, connect to GND of your adapter
S2 UART2_RXD, connect to TX of your adapter
S2 UART2_TXD, connect to RX of your adapter
S1 GND, connect to GND of your adapter
S1 UART1_RXD, connect to TX of your adapter
S1 UART1_TXD, connect to RX of your adapter
Processor module card:
RK3588 S1 @ 1500000 baud
i.MX 8M Plus S2 @ 115200 baud
RCM4-BPi/A311D S2 @ 115200 baud
Serial Wire Debug (SWD) on SYS MCU
On test pads:
SWC -> TP6
SWD -> TP5
Internal connections
SYS MCU
I2C - SDA0/GPIO0, SCL0/GPIO1; 3.3V STANDBY
Qwiic
Charger board:
MAX17320G20+ - Battery Fuel Gauge
MP2650 - 5A Buck or Boost Charger
UART1 TX/GPIO4, RX/GPIO5
Keyboard
UART2 TX/GPIO12, RX/GPIO13
SoM as UART3_TXD/RXD -> UART0_TX/RX_M2
USB
RUD+/USB_DP, XUD+/USB_DM - Got to SoM but can go to internal USB-C port for direct flasing depending on USBSEL/J21 jumpers
This is accessible from Linux as ACM UART and can be used to see debug messages from MCU and issue commands (if support is compiled in)