DLINK DIR-842 C1 TTL RX pin not working


In a DIR-842 C1 router i can able to see serial log but cannot send command.
I wonder if somebody else has a same problem or it is a hardware fault in my router with the TX pin?


Short your serial RX and TX pins, can you see your own typing in the terminal window ?
If yes, then at least your serial cable works.

In some cases u-boot serial input is disabled by default, it have to be enabled by modifying
the u-boot params (from within the router OS).

No need for serial for openwrt installation though

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Thank you for your help.

TTL adapter is good i just used in other devices and tried 4 different one.
Thanks for te idea hopefully it is a U-BOOT parameter just. i need to check how this U-boot setting work.

Yes i already installed but like to have a backup to log in in case of i mess up something.

Seems to be a dead end.

You'd probably have to replace the u-boot if you want RW.

You can always use the d-link recovery, if you screw up your openwrt
AND the serial will still work for openwrt, even if the network is dead.

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did you check you voltages
is you board +V5 +3.3 +1.8 ect
do you have the correct ttl voltage level ?

I wonder if there is a good description how to replace u-boot?

yes i measured 3.3v

It'll probably be harder to find a working u-boot for the device, then getting it in place, the latter can be done through OpenWRT.

If you screw up the u-boot, you'll have a nice paper weight on your hands, unless you want to play
around with SPI programmers and such.

With a bit of luck you might be able to replace u-boot with Breed. It's a bit risky (but not any riskier than trying to get another u-boot on there).