GL-MT300N-V2 is the second serial port available?

How can I use it ?
CK and SD pins are for i2c ?
How can I use it ?
Thank You

It is GPIO and can be used for I2C.

It depends on what you want to use it for. Without know the aim cannot answer your question.

I am using the second serial port /dev/ttyS1 on a GL-MT300N-V2 running openwrt-18.06 snapshot. It “just works”. I haven’t tried with the stock firmware.

Have a look in the syslog to see if it is enabled on boot for your system. I see a line

10000d00.uart1: ttyS1 at MMIO 0x10000d00 (irq = 29, base_baud = 2500000) is a 16550A

just after /dev/ttyS0 is enabled.

I am working with a GPS module that transmits as the router boots. This stopped uboot when connected to /dev/ttyS0.

I want to connect an arduino mini pro 3.3v to second serial port.
I want to connect an Raspberry Pi Zero 3.3v to first serial port.
How to make the switch to be in one position console for openwrt ( if i need for GL access )
and in the other position to be simple serial port ?
Thank You
P.S. On USB port will be a 3G modem…

@billingd which target to choose from 18.06 ?
Is ramips mt7628-squashfs-sysupgrade.bin or gl-mt300n-v2-squashfs-sysupgrade.bin ?
Thank You

@florinel I suggest you try the stock firmware first. Have a look at the kernel log and see if /dev/ttyS1 comes up on boot. I am only using a snapshot because I need to recompile the kernel for another reason.

I am using gl-mt300n-v2-squashfs-sysupgrade.bin. Be warned - it is updated every couple of days and if you want to install kernel modules you need to be running the latest version. I haven’t found any issues in a week of playing around with GPIOs and serial ports. I haven’t enabled wireless or used the device as a router.

/dev/ttyS1 doesn’t apear in kernel log
I’ve found an old post (with older firmware) where was recommended to recompile the kernel …
I will try gl-mt300n-v2-squashfs-sysupgrade.bin.
Thank You

@florinel Did you try the latest (2.27) gl-inet firmware?

Looks like the second serial port was enabled with a patch to on 2018-02-23 (I noticed this as I am messing around with this .dts file)

The latest firmware from GL.iNet download center is lede-mt300n-v2-2.27.bin from 2018-04-13

No ttyS1
“root@GL-MT300N-V2:~# logread | grep -i tty
Tue May 15 14:55:15 2018 kern.notice kernel: [ 0.000000] Kernel command line: console=ttyS0,115200 rootfstype=squashfs,jffs2
Tue May 15 14:55:15 2018 kernel: [ 0.274402] console [ttyS0] disabled
Tue May 15 14:55:15 2018 kernel: [ 0.277894] 10000c00.uartlite: ttyS0 at MMIO 0x10000c00 (irq = 28, base_baud = 2500000) is a 16550A
Tue May 15 14:55:15 2018 kernel: [ 0.286600] console [ttyS0] enabled”

I’ve put gl-mt300n-v2-squashfs-sysupgrade.bin and second port works.(Thanks !)
Now I try to use first serial port (console) …
If it doesn’t work I’ll have to use an USB hub :frowning: