Debricking Netgear DM200 modem

I recently purchased a Netgear DM200 from ebay and accidentally bricked it after attempting to flash it with OpenWrt 22.03. It’s unclear if this was due to not fixing the u-boot configuration to support larger kernels or restarting the device too early after flashing. When I turn it on now the power light flashes green and I can no longer connect to the web interface at or ssh at Holding down the reset button on the device doesn’t seem to have an effect. I can ping it at, as mentioned in this solution, but am unable to flash firmware at that IP.

$ ping
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=64 time=2.343 ms
64 bytes from icmp_seq=1 ttl=64 time=0.344 ms
64 bytes from icmp_seq=2 ttl=64 time=0.330 ms
# nmrpflash -i en1 -a -f DM200-V1.0.0.66.img
Waiting for Ethernet connection (Ctrl-C to skip).
Error: Ethernet cable is unplugged.

I’m not very familiar with hardware but opened up the device and the only internal two ports I could find are labeled JP1 and R145. Any ideas on how to fix? It only cost $20 so I could just try again with another device but would prefer not throwing it out if I don’t need to.

I've debricked one of those using nmrp flash.

Download the latest Netgear firmware from their website. Unzip and follow the nmrp flash instructions to go back to netgear firmware. Once that works you can flash OpenWRT again.

Otherwise you will need a serial / UART cable and connect it to the pins on the board.

The four pins on the board are GND → TX → RX → 3v3 from bottom to top according to the device page.

Do not connect the 3v3 when using serial!

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Following the instructions verbatim on the nmrpflash README allowed me to restore. Turns out I was using the wrong interface.

It looks like this was due to the u-boot configuration, which will require a serial cable to fix. Am going to order this one but in the meantime am successfully running openwrt 18.06.

Update: The serial cable linked above and following the instructions on the wiki with picocom allowed me to successfully upgrade to the current release, 22.03.5. There was no soldering required.

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