I’m trying to identify the UART serial console on a Linksys EA6900 v1.1 and would appreciate any help from someone who has worked on this board before.
Router
Linksys EA6900 v1.1
PCB marking: 94V-0 48348406CG
Broadcom-based
What I’ve done so far
Using an FT232RL USB-to-TTL adapter configured for 3.3 V logic.
Connected GND only (no VCC connected).
Identified the GND pin with a multimeter.
Found one pin that idles around 3.3 V and changes voltage during boot, so I suspect it may be TX.
Tried both TX/RX combinations.
Tested 115200 8N1 in PuTTY (also tried a few other common baud rates).
I get no output at all during boot.
The board has a 6-pin header that I believe may be the UART connector, but I’m not sure of the pinout.
I’ve attached:
High-resolution photos of both sides of the PCB.
Close-up photos of the 6-pin header.
Has anyone identified the UART pins on this revision of the EA6900, or can anyone help determine the pinout from the PCB? Is it possible that the serial console is disabled or uses a different baud rate?
Any advice would be greatly appreciated. Thank you!
It's been so long since I had an EA6700 that I don't remember, but I guess these have the same header and pinout as the WRT1900AC etc. See
But do test and verify that guess with your multimeter!
You won't break anything as long as you get the IO voltage correct (3.3V or 1.8V) and don't mix up VCC and GND. And all of that is simple to verify with a multimeter before connecting the uart usb adapter
Thanks! You were right—the 6-pin header and pinout matched.
It turned out my problem wasn't the pinout at all, but the improvised wires I was using to connect my FT232RL to the UART header. Once I fixed the connection, the serial console came up immediately.
I can confirm the pinout is:
Pin 1 – GND
Pin 2 – TX
Pin 3 – N/C
Pin 4 – RX
Pin 5 – N/C
Pin 6 – 3.3 V
(115200 8N1, 3.3 V TTL)
Once I had the serial console working, Claude Code did most of the work from there. I was able to access the bootloader and successfully flash OpenWrt using the ASUS RT-AC68U (BCM4708) image.
The router is now running OpenWrt. The only thing not working at the moment is Wi-Fi, which I expected since the wireless drivers for this hardware aren't supported yet.
