Recovering MT300N Using Serial

Technical Support for Routers
1

I was building a new version of openwrt for the MT300N devices that we use and messed the build up, locking myself out of the device somehow. I suspect a network config error. Typically, I put those aside, fix the problems and move on to the next device. I wanted to see just how hard they would be to recover and tried all of the variations I could find in terms of resetting it but nothing works.

Now I want to see if I could recover it since it has serial pins already installed. I have a USB/TTL cable installed on a win7 PC and connected to the device. Tx/Rx/Gnd, 115200, 8N1. Again, nothing. Not even garbage on the screen.

 

Two LEDs come on when starting the device, then one remains on for good. No other changes no matter what I try.

 

Wondering if anyone might have some thoughts.

 

 

2

Anyone here???

3

The settings is fine. Make sure your adapter uses 3.3V not 5V.

Check the docs to see if it helps.

4

Do you mean to power the device? I’m powering the device using the mini usb port so only have Tx/Rx and Gnd connected.

The cable is a FTDI Chipset PL2303HX

 

5

I mean the USB uart adapter.

What is the chip of your adapter? Can you show a link? Is the rx and tx connected correctly?

6

Tx is green, Rx is white, Gnd is Black. Output voltage on this TTL connector is 5V which I’m not using.

Chip says PL-2303HX.

Running the prolific test however show PL2303 XA/HXA.

7

If I can recover this device, I will see if we can start using it as our default one since 1GB NICs are coming.

At some point, we’ll want a custom version of the whole thing but right now, orders would be based on how many any one customer wants. 1, 5, 100, 500, etc. Most will only want one or a few at a time.

8

I tested the same connection/cable on a brand new MT300N and no output what so ever. I think this cable is garbage.

 

9

If the device still power on (led light up), it should still be live.

One question, the green wire (tx on MT300N) should connect to the RX of your adapter, right? Sounds stupid but it must be made sure.

Second question, when you use a serial term and connected to the USB uart adapter, when you type in the term windows, did you see the USB uart adapter has some LED flashing? Generally when data is transferred, the adapter has an LED indicating the data. This is to make sure your adapter has good connection with your computer.

10

Green is Tx on the adapter and is connected to Tx on the MT300N. I’ve tried reversing the Tx and Rx. I should at least be able to get garbage but get nothing what so ever.

11

According to here: Overview - GL.iNet Docs

TX must be connected to RX

RX must be connected to TX

Make sure the connection is correct and try to play for a while.

12

Yes, I’ve done that. I also took the ttl adapter apart to check and could see the wires labeled. I tried both ways.

13

can you send a online link about the adapter of you are using? Maybe ebay or amazon link.

14

Strange, it worked in reverse as you said. It just took several minutes to show anything in the terminal.

Now I need to figure out how to login to the device in order to make the changes. It seems the network is messed up and ssh is disabled.
Seeing ARP request weirdness.

15

From serial, no login needed.

Check the docs about uboot: Overview - GL.iNet Docs

 

16

Understood. The only problem is the device seems stuck in a loop, rebooting over and over again.

17

I think you mean it boots into openwrt then reboot.

In this case, just stop the booting process in uboot and change the firmware.

18

Finally getting some better input now. I’ll post what I’m seeing shortly.

19

T T T T T T
Retry count exceeded; starting again
ArpTimeoutCheck
TFTP from server 192.168.1.2; our IP address is 192.168.1.1
TIMEOUT_COUNT=10

Load address:0x80100000
Load filename:openwrt-gl-mt300n.bin

Loading: [08]T T T T T T T T T T
Retry count exceeded; starting again
ArpTimeoutCheck
TFTP from server 192.168.1.2; our IP address is 192.168.1.1
TIMEOUT_COUNT=10

Load address:0x80100000
Load filename:openwrt-gl-mt300n.bin

Loading: [08]T T T T T Got ARP REQUEST, return our IP
T checksum bad
Got ARP REQUEST, return our IP
checksum bad
checksum bad
T Got ARP REQUEST, return our IP
Got ARP REQUEST, return our IP
T T T
Retry count exceeded; starting again
ArpTimeoutCheck
TFTP from server 192.168.1.2; our IP address is 192.168.1.1
TIMEOUT_COUNT=10

Load address:0x80100000
Load filename:openwrt-gl-mt300n.bin

Loading: [08]T T T

 

20

your tftp server is not running properly. It cannot connect. Be sure to follow the docs carefully.

I think you can try uboot webUI first. Keep the reset button pressed when powering on the device will enter uboot webUI