The board exposes a serial interface. Parameters are 57800,8N1. The board draws about 250mA and I even had to increase the current limit of my power supply to 500mA before it booted. Which means you need a separate power supply as most cheap USB serial adapters are only capable of delivering 100mA.
The output during boot shows, that it’s actually booting u-boot:
[04060C0D][04060B0F] DDR Calibration DQS reg = 00007E89 U-Boot 1.1.3 (Jan 24 2018 - 12:18:18) Board: Ralink APSoC DRAM: 8 MB relocate_code Pointer at: 807b8000 flash manufacture id: c2, device id 20 15 find flash: MX25L1605D ============================================ Ralink UBoot Version: 220.127.116.11 -------------------------------------------- ASIC 7628_MP (Port5<->None) DRAM component: 64 Mbits DDR, width 16 DRAM bus: 16 bit Total memory: 8 MBytes Flash component: SPI Flash Date:Jan 24 2018 Time:12:18:18 ============================================ icache: sets:512, ways:4, linesz:32 ,total:65536 dcache: sets:256, ways:4, linesz:32 ,total:32768 ##### The CPU freq = 580 MHZ #### estimate memory size =8 Mbytes RESET MT7628 PHY!!!!!! Please choose the operation: 1: Load system code to SDRAM via TFTP. 2: Load system code then write to Flash via TFTP. 3: Boot system code via Flash (default). 4: Entr boot command line interface. 7: Load Boot Loader code then write to Flash via Serial. 9: Load Boot Loader code then write to Flash via TFTP. default: 3 You choosed 3 3: System Boot system code via Flash. ## Booting image at bc050000 ... Image Name: zxrouter Image Type: MIPS Linux Standalone Program (uncompressed) Data Size: 742084 Bytes = 724.7 kB Load Address: 80500000 Entry Point: 80500000 Verifying Checksum ... OK OK
The board then drops into command line mode. Hitting ‘4’ during the boot process takes us to the u-boot prompt:
You choosed 4 4: System Enter Boot Command Line Interface. U-Boot 1.1.3 (Jan 24 2018 - 12:18:18) MT7628 # help ? - alias for 'help' bootm - boot application image from memory cp - memory copy erase - erase SPI FLASH memory go - start application at address 'addr' help - print online help loadb - load binary file over serial line (kermit mode) md - memory display mdio - Ralink PHY register R/W command !! mm - memory modify (auto-incrementing) nm - memory modify (constant address) printenv- print environment variables reset - Perform RESET of the CPU rf - read/write rf register saveenv - save environment variables to persistent storage setenv - set environment variables spi - spi command tftpboot- boot image via network using TFTP protocol version - print monitor version MT7628 # print bootcmd=tftp baudrate=57600 ethaddr="00:AA:BB:CC:DD:10" ipaddr=10.10.10.123 serverip=10.10.10.3 BootType=3 bootdelay=1 stdin=serial stdout=serial stderr=serial
Now, tftpboot would be fine, but of course we have no network connection
here. However, the ‘
loadb’ command looks promising.