I need help gaining access to the TTL Serial port on the CG3000D

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LightworkerNaven's picture
I need help gaining access to the TTL Serial port on the CG3000D

Hey, I originally posted this on the Netgear forums, but they suggested that I post it here.


Hey, I want to create custom firmware for the CG3000D modem so people can have more access to their modem/router like how DD-WRT allows people to have more control over many routers. In order to do this, I need access to the TTL serial port.

I already got it pinned out and I hooked up a USB to UART serial connector to it and I get binary crap spilling onto my PuTTY terminal when I turn the modem on and connect really fast. That means its able to communicate properly, but as PuTTY needs to have the modem up in order to connect to it, it might be connecting too late to get the output and display it properly. It eventually stops spilling binary junk to the screen and goes quiet.

When I wait for it to be connected to the internet and then use PuTTY to connect, then it gives me a blank screen, so I think I need to talk to it to get it to respond, but I tried typing enter and nothing comes out on the screen.

So, the questions I have, are:

1.) How do I set up the connection to the port properly. Do I need to configure a handshake somehow?

2.) PuTTY is what I've been using, but is there a different connection terminal you recommend?

3.) Can the MIPS JTAG or the TTL Serial ports on there, be disabled by the firmware? (I'm imagine not as they should be talking directly to the hardware and not routing through firmware, but its better to ask and be on the safe side.)

4.) Am I only able to connect on the TTL serial port at a certain point in the start up process? Also, do i need to have only the power and TTL serial adapter connected to the device or can I leave the cable line and ethernet cable connected as well? (I don't know if it kind of works like BIOS where it checks for the first bootable media and allows you to boot from the DVD ROM as well.)


Here's what I'm working with.

1.) Adapter: USB 2.0 to UART TTL 6PIN Connector Module Serial Converter Buildin-in CP2102 (I used the driver that Windows 7 recommended.)


2.) PuTTY 0.62

3.) Here's the pin out of both the adapter and its corresponding pin out on the TTL Serial port



LightworkerNaven's picture
Thank you. I'm reading that

Thank you. I'm reading that now. Also, I found that I need to have it set to 115200 bps and I need to connect right away when it boots, but its giving me this message at the end, Any idea why?

"[00:00:00 01/01/1970] [tStartup] BcmEpsCmDocsisSystem::Initialize: (BFC System) ERROR - Disable console port now!"


For those of you who found this on Google and want to know what happened, the console port/TTL serial port of the CG3000D was disabled by the firmware and that last message really did mean it got disabled and not that it was a request to disable it before it could go any further. So, I'm onto the MIPS EJTAG connector as the last way to connect to it and that one can't be disabled by the firmware. I'll be using USB JTAG NT to do so.

Here's the link to the conversation I had about that.