Trying to connect to a Routerboard 750 using the serial interface. Soldered wiring to RX/TX and GND and connected to a Serial to USB converter. Using Putty I'm not able to connect to the Routerboard, can anyone help me? The USB converter is visible in the device manager...... Thanks in advance.
I suspect you are running Windows, what kind of serial adapter is it, there are a lot of them. Generally speaking, there is one that has the RS-232 standard. But the one that we most often use these days is more of a Serial TTL Level UART USB adapter, it also usually has two different voltage levels, 3.3v and 5v. So you have to know what voltage level the UART is working on. That was the first thing, when it comes to Windows and serial adapters, you have to look at the COM ports that are created via the driver, and then choose the correct COM port on Putty. And of course also the correct baud rate, etc. It can also be which handshake variant you choose, when it comes to UART, when you have only connected reception and transmission and ground, you usually choose none handshake.
Do you have the RB750Gr3 named HEX ? or the old models ?
https://openwrt.org/toh/mikrotik/rb750gr3
https://openwrt.org/toh/mikrotik/rb750gl
Thank you for the quick reply.
Followed the configuration steps displayed in:
https://www.youtube.com/watch?v=HYFUuxGHdoI
Am using the USB-Serial converter:
USB-COM232-PLUS1 FTDI, Adapter Board, FTDI Chip, USB to RS232 | Farnell Nederland
The USB-Serial converter is visible in the device manager (COM5) / WIN10.
Thats bad, this is a RS-232 serial device. With the DB9 connector.
Maybe you have break your RB750, because of the HIgh voltage from the RS-232 pins.
And lots of Routers console port is RS-232. like the Video says.
RS-232 uses like +3v -- +15v for "1"
and -3v -- -15v for "0"
You need a TTL level USB UART Adapter to get it working.
TTL Level uses like +3.3v -- +5v for "1"
and 0v for "0"
Which EXACT board are you trying to access?
Rx/Tx/Ground exposed on a board are generally speaking NOT RS232, but rather UART/TTL, with a much lower voltage, either 3.3V or 5V peak.
A RS232 is usually 12V or 15V.
(and besides it has inverted logic)
Please be aware that (it is confusing, I know) in the UART/TTL world there are 3 (three) types of connections:
- pure TTL 3.3V <- won't fry anything but might not work if the other side is 5 V
- TTL 3.3V, 5V tolerant <- won't fry anything but might not work if the other side is 5 V
- pure TTL 5V <- might fry 3.3V logic on the other side
It has happened to fry boards even using a "pure 5V" voltage on a "pure 3.3V" port, and there are also 5V CMOS levels (rare nowadays), see:
https://i.sstatic.net/4h1WO.png
serial output is disabled in boot code
look at OpenWRT forum
you need to
- load initramfs in RAM
- config bits to enable serial
- write modified config to flash