No data visible via the serial interface of the SERCOMM NA502 gateway

Installing and Using OpenWrt
1

Hello,

I am trying to establish a serial connection to https://openwrt.org/toh/sercomm/na502#tftp_installation_instructions.
Unfortunately without success.
The terminal screen remains blank.
If I change the baud rate to something other than the defined value, at least confused characters are visible, which in my opinion at least indicates an intact electrical connection, or not?

Does anyone have any ideas on how I can proceed with troubleshooting?

Many thanks in advance.

/Cipo

p.s.: I have tried it with two different computers or different terminal software. Always the same result.

2

Different computers, but same USB TTL ?

3

Yes, but that's the next thing I want to replace in terms of a step-by-step approach :wink:

4

try shortening the Tx and Rx pins on your USB TTL, you should be able to see your own writing in Putty, or whichever application you use.

5

Thanks for the tip. I'll try it out right away. :hugs:

6

Thank you again. As you can see, the return loop seems to be working ... so now it's time to check the connection between the adapter and the serial port of the gateway.

I'll probably best re-solder the solder joints to be on the safe side.

image
image1564×840 109 KB

7

As a precaution, I would like to ask whether I have interpreted the description of the pin assignment of the serial interface of the Sercomm gateway correctly. See the following picture:

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image1920×1440 135 KB

Thanks :pray:

8

Looks OK to me, but then again I don't own one.

9

Sorry, I must have forgotten that in my desperation :wink:

Anyway, it looks like the serial connection should work in principle. However, the console does not behave as I would have expected from the installation documentation, namely:

  • When GW-TX is connected to USB-TTL-RX before turning on the gateway, no data is visible and the LEDs do not light up. The gateway does not appear to start.

  • When GW-TX is connected to USB-TTL-RX after the gateway is powered on, the screen is also blank, but after pressing the reset button, the button press is recognized and the reboot process is logged on the screen, and a series of messages can be seen, and somewhere in between is the text "1: Load system code to SDRAM via TFTP".

Is this behavior considered "normal"?

If so and everything is OK so far, the question arises as to how the TFTP server must be connected to the gateway. Direct point-to-point connection with static IP addresses or via the home network?

10

Don't know about normal, but it matches the wiki entry you linked to.

Once you select 1, all the info you need should be displayed by the boot loader.

Doesn't matter how you connect it, but 1:1 is obviously the safest.

11

Did you try swapping Tx and Rx? And no, the LED behavior should be the same no matter whether the UART is connected or not - as long as you don't send anything.

12

So far, the bootloader has unfortunately not responded after entering "1"

OK, I see. Now I just have to find the right IP settings. Provided the bootloader starts to interact with me :wink:

13

You probably should start hammering the 1 key before you actually see the output.

14

Yes, but nothing was visible on the screen.
Just to be sure, I'll try it again.

That's good to know. :+1:
However, this is not the case at the moment. Unfortunately, it behaves as described above.

15

You have to be really quick, but your tip seems to be working ...

1: System Load Linux to SDRAM via TFTP.

Please Input new ones /or Ctrl-C to discard

Input device IP (192.168.1.254) ==:192.168.1.254

Do I understand the message correctly that I have to provide the TFTP server at address 192.168.1.254?

16

I have now tried swapping the TX and RX lines again, but as described above, the screen remains blank. Regardless of whether PowerUp or Reset triggers the boot/reboot.

17

Or provide a different IP.
This could also be the client IP, trial and error.

You can't really break anything here, by providing incorrect info.

18

I am really desperate, whatever is messing up the system here ...

Now I can at least get to the selection in the Uboot menu, but the values cannot be deleted or overwritten. No matter what values I enter, they seem to be added somehow.

Does anyone have any ideas?

How can the default values normally be corrected or overwritten?

e[31m******************************************
    Uboot StandAlone Entry
******************************************e[0m
0, cmd
1, 0x0000000D
cmd : 0x0000000D
You choosed 1
 0 
 1: System Load Linux to SDRAM via TFTP. 
 Please Input new ones /or Ctrl-C to discard

	Input device IP (192.168.111e192.168.1 192.168.1.181) ==:192.168.111e192.168.1 192.168.1.181

	Input server IP (192.16 192.168.1.196) ==:192.16 192.168.1.196

	Input Linux Kernel filename (192.168.1.2 ) ==:192.168.1.2
19

Try using the suggested values, even though they look wrong ?

20 
ETH_STATE_ACTIVE!! 
TFTP from server 192.16.192.168; our IP address is 192.168.111.192
Filename ‚192.168.1.2 ‚.

U-Boot obviously tries to extract valid addresses from the strings, even if they are wrong.
How the IP address gets into the prompt for the filename is also inexplicable.

In the end, it can't work that way either ... :worried: