How to use the serial debugging cable on VIM3 Pro board

Dear technical support engineer,

I bought the “USB to TTL serial UART RS232 adaptor” for debugging VIM3 pro board.
The product has four wire: red power, black ground, white RX, and green TX.

I read the below web-pages to use the serial cable to do a debugging after flashing
Ubuntu image (VIM3_Ubuntu-xfce-bionic_Linux-4.9_arm64_SD-USB_V20190830.7z) into micro-SDcard for VIM3 Pro development board.

BTW, It is weird. The below webpage provides customers with the incorrect manual.

For example, according to the manual, we have to connect the USB serial cable to Pin17(GND), 18(RX), 19(TX).
Pin17 of VIM3: GND
Pin18 of VIM3: Linux_RX
Pin19 of VIM3: Linux_TX

In this case, the terminal does not print any messages while booging Ubuntu on VIM3 pro board.
When I tried to connect the USB serial cable to Pin18(GND), 19(RX), 20(TX), the terminal prints the booting messages normally.
Pin18 of VIM3: GND
Pin19 of VIM3: Linux_RX
Pin20 of VIM3: Linux_TX

However, I could not still type keys with a keyboard on VIM3 Uboot prompt.
--------------------------- booting message: start ---------------------------
… Omission …
HPLL: 0x3b3a04f7
HPLL: 0x1b3a04f7
HPLLv1: 0xdb3a04f7
config HPLL done
j = 6 vid_clk_div = 1
hdmitx: set enc for VIC: 16
hdmitx phy setting done
rx version is 1.4 or below div=10
vpp: sdr_mode = 2
vpp: Rx hdr_info.hdr_sup_eotf_smpte_st_2084 = 0
normal power on
boot wol: disable
saradc: 0x289, hw_ver: 0x32 (VIM3.V12)

gpio: pin GPIOAO_7 (gpio 7) value is 1
port mode is usb3.0
Command: bcb uboot-command
Start read misc partition datas!
BCB hasn’t any datas,exit!
--------------------------- booting message: end ---------------------------

Hit Enter or space or Ctrl+C key to stop autoboot – : 0

For example, If I type “run update” messages on “kivm3#” prompt,
the result is as follows. How do I fix this issue? Welcome to any hints.


Geunsik Lim.

Here is a screenshot.

No, you can’t do this. The pinout is correct. PIN17 must connect to the GND.

PIN18 for VIM3 is Linux_RX, so you need to connect it to the TX of the USB to TTL serial UART RS232 adaptor.

PIN19 for VIM3 is Linux_TX, so you need to connect it to the RX of the USB to TTL serial UART RS232 adaptor.

You need to swap the TX and RX.


Thank you for you fast reply. It’s okay with your clean reply. :slight_smile: