AmplifiHD Router and OpenWRT - Installation and fixing boot

gistfile1.txt

# Here's step-by-step how I got OpenWRT on my Amplifi HD Router
# There are some steps to this and one of them is HW access to the Serial interface on the PC.
# This is found here:

1. Open the Router and connect a UART/Serial USB to between PC and Router
   Note that in my case the pinout was mirrored.
   It is located on the middle print. 

Details for step 1: https://github.com/alexanderhenne/AFi-R?tab=readme-ov-file#finding-j11

2. Download OpenWRT kernel image and TFTP it to the router.
   When booting the image, beware that I had to change the bootm address to something higher 
   (i.e. tftpboot 0x83000000 amplifi-router-hd-initramfs-kernel.bin
         bootm 0x83000000)
   as the kernel image fail decompress.v
   Then scp the squashfs-sysupgrade image to the router and write to partition.

Details for step 2: https://github.com/openwrt/openwrt/commit/c5b7ec8cee497c3a84eb8ad90d88494f0812698c
   
3. Modify uboot parameters! Now I couldn't get it to boot to openwrt initially. I figured it
   had to do with the uboot configuration. There was no guide available for this so I will write the
   steps out in detail.
  
  3.a. Stop the device from normal boot by pressing "ESC" on the Serial connection. 
  3.b. Now we change the bootcmd from its default to point towards the new flashed firmware location.
       > setenv customboot 'bootm bf070000'
       > setenv bootcmd 'run ubntappinit customboot'
       > saveenv
  3.c. Reboot device to verify that it boots openwrt:
       > reset
       
  N.B. For this step, please verify that the firmware partition is infact at address bf070000. This can
       be done by running the ubntappinit and see that name firmware has start_addr:
       > run ubntappinit
       .....
        2. Name = firmware, offset = 70000, start_addr=bf070000, size=11534336,start_sector=7, end_sector=182 
       .....

Hi, thanks a lot for this guide. I am a noob at OpenWRT and routers and have a few questions. It'd be great if you'd look into it:-

1. Does the GND from router go to my Serial reader's GND? Asking cause alexander's guide says, "It's recommended to connect GND of your UART reader to the shield of your router's power connector rather than to the header's GND."
2. Is Reset + Power on still the preferred method to put the Amplifi HD in TFTP mode?
3. Doesn't the router autoflash the kernel-initram image after it's TFTP'ed? Is this why the tftpboot command is required?
4. Scp sysupgrade - Should it be done on the serial console or on the host terminal?
5. Step 3a: Do I boot the router normally here? Or, with the reset button pressed?
6. Can I run similar steps to revert back to original firmware?
7. Is there a clean way to disassemble Amplifi HD? Couldn't find clear info anywhere.

Thanks again, and am sorry for the noob questions.

Hi, thanks a lot for this guide. I am a noob at OpenWRT and routers and have a few questions. It'd be great if you'd look into it:-

1. Does the GND from router go to my Serial reader's GND? Asking cause alexander's guide says, "It's recommended to connect GND of your UART reader to the shield of your router's power connector rather than to the header's GND."

2. Is Reset + Power on still the preferred method to put the Amplifi HD in TFTP mode?

3. Doesn't the router autoflash the kernel-initram image after it's TFTP'ed? Is this why the `tftpboot` command is required?

4. Scp sysupgrade - Should it be done on the serial console or on the host terminal?

5. Step 3a: Do I boot the router normally here? Or, with the reset button pressed?

6. Can I run similar steps to revert back to original firmware?

7. Is there a clean way to disassemble Amplifi HD? Couldn't find clear info anywhere.

Thanks again, and am sorry for the noob questions.

I have ran the UART successfully and can answer some of the questions. So, here goes.
1- GND from router should go to Serial reader's GND. And, in my case, same as Stephen, the pinouts are reversed - RX in the image is TX, TX in the image is RX and VCC in the image is GND.
4-The scp command has to be run on your PC (host's) terminal. On Windows, that'd be Command Prompt. The mtd command has to be done on the serial console.
6- Wild guess. A firmware backup (cat /dev/mtd6 > /tmp/original-firmware.bin to back it up before installing OpenWRT) could technically be rewritten to the router using the mtd write command. Not sure. Please correct me if I am wrong.
7- Depends on your skill. You have to go from down up. Here's a quick guide - Used a few small flat headed screwdrivers and pried it open. The rubbery/plastic plate underneath is attached to everything inside. But, to open it, you have to first pry it open a little to get access to the white plastic plate and find the clips at almost the center on each side. Pry them a little such that the inside compartment comes loose a bit. Repeat for the other 3 sides. Carefully pull everything from inside. There's only one cable running from the outer shell to the board which connects display and speaker. Take care to not rip it off.

Too answer some of your questions, that you didn't answer your self :)
2. I just used regular boot and then canceled the regular boot procedure before uboot started booting the linux image.
3. Don't know :)
5. Yes, boot normally and again interrupt regular boot procedure by spamming "ESC" button in the terminal while it is in uboot, i can't remember for sure, but i believe you have a couple of seconds.
6. I guess you're right, but I have not tried that myself. Also I think you could use the image from ubiquity and then manual flashing procedure as well.
7. Good write up. I had some trouble with prying the plastic apart so the tabs on the transparent part broke for me unfortunately, but it only affects appearance fortunately.

Hope this helps, sorry for the delayed response and good job figuring it out 👍

Too answer some of your questions, that you didn't answer your self :) 2. I just used regular boot and then canceled the regular boot procedure before uboot started booting the linux image. 3. Don't know :) 5. Yes, boot normally and again interrupt regular boot procedure by spamming "ESC" button in the terminal while it is in uboot, i can't remember for sure, but i believe you have a couple of seconds. 6. I guess you're right, but I have not tried that myself. Also I think you could use the image from ubiquity and then manual flashing procedure as well. 7. Good write up. I had some trouble with prying the plastic apart so the tabs on the transparent part broke for me unfortunately, but it only affects appearance fortunately.

Hope this helps, sorry for the delayed response and good job figuring it out 👍

Thanks a lot for this. I was able to boot the initram-kernel image successfully, but, I really wanted to somehow get the copy of the mtd6 (original firmware) backup to my local machine before I finalised the upgrade with scp. Anyways, when I was on booted initram-kernel, I wasn't able to access the Web admin GUI with the IP/the gateway. I guess, this would only be available after I did the scp upgrade.
Also, I plan on doing a detailed guide once I have everything setup, given everything goes well. Thanks a lot for this guide.

Update - Was able to scp upgrade to the OpenWRT build. And, used the backed up firmware to try and revert to original Amplifi firmware. It worked flawlessly!
As for the Admin GUI, my bad. Didn't know Luci had to be installed separately. Did that when on the WRT build and it functioned as expected.