UART Guide¶
The ZTE MF286D exposes a serial console on the internal X8 header. It is the recovery path when the router does not boot, and the required path for first-time installation.
Connector¶
X8 is a 4-pin header. Pin order, from the pin closest to the X8 silkscreen label
to the farthest:
| Pin | Signal |
|---|---|
| 1 | VCC (3.3 V) — do not connect |
| 2 | TX |
| 3 | RX |
| 4 | GND |
Serial settings¶
115200 baud, 8 data bits, no parity, 1 stop bit (8N1)
Use a 3.3 V USB-to-serial adapter (for example a CP2102 or FT232RL board set to 3.3 V). Do not connect the VCC pin; power the router from its own supply.
Wiring¶
| Adapter | Router X8 |
|---|---|
| GND | Pin 4 (GND) |
| RXD | Pin 2 (TX) |
| TXD | Pin 3 (RX) |
If you see nothing, swap TX and RX.
Accessing U-Boot¶
- Open a serial terminal at
115200 8N1. - Power on the router and press a key repeatedly to interrupt autoboot.
- You should get the U-Boot prompt.
From U-Boot you can load an initramfs image over TFTP and boot it:
setenv serverip 192.168.1.3
setenv ipaddr 192.168.1.72
set fdt_high 0x85000000
tftp openwrt-ipq40xx-generic-zte_mf286d-initramfs-fit-zImage.itb
bootm $loadaddr
Opening the case¶
From the upstream support commit:
- Remove the battery lid (the battery cage is a dummy on this model).
- Unscrew the screw behind the battery lid.
- Remove the back cover; it is held by plastic clamps.
- Unscrew the four screws hidden behind the back case.
- Remove the front panel from the blue chassis (more plastic clamps).
- Unscrew the two boards securing the PCB.
- Lift the board out of the chassis.
The X8 header is on the main board. Work on an anti-static surface.