Raspberry Pi 4B + 2x MT7612U

[TrylobitBroccoli]

Hi!

I wanted to create a Wifi to Wifi travel router. The integrated Raspberry Pi 4B wifi is not the greatest, so I got 2 Alfa AWUS036ACM.
And it crashes under load non-stop. Most of the time I can't even finish a speed test.

Is there a solution to this?

I've read this thread and it seems like it's a dead end... openwrt/mt76#405

[Thimbles809]

Are you doing dual band? We've been going over that in this ol thread here using Raspberry OS on a pi 4.

#200

I haven't experienced any crashing under load issues. Got any /var/log/syslog output around the time of crash? It could be a power issue, though both the ACM's are 400ma a pop.

Are you using a USB hub? And did you peruse the guide?
https://github.com/morrownr/USB-WiFi/blob/main/home/AP_Mode/Bridged_Wireless_Access_Point.md

There's a section there on the Scatter-Gather parameter you may want to check into, more detail here:
https://github.com/morrownr/7612u

[TrylobitBroccoli]

I'll do a fresh OpenWRT installation and look for log.

I am not using a hub. It should it be fine without power-wise. I have one HUB, but I think it's feeding back power as sometimes it works other times the USB adapters don't show up or only one shows up.

I have just used this guide, but this is all new to me, so I did the guide https://github.com/morrownr/USB-WiFi/blob/main/home/AP_Mode/Bridged_Wireless_Access_Point.md but it looks to me like it end without setting up the Client side and the AP side :)

I am a newb in this matter - I installed OpenWRT on a router for my inlaws and it worked flawlessly.

I did turn off Scatter-Gather, but in a different way. I will make a fresh OpenWRT installation and follow this guide: https://github.com/morrownr/7612u

[bjlockie]

I only used 5ghz for my AP so I wonder if that lessens the problem.

[morrownr]

@bjlockie

It can be hard to determine what reduces problems related to RasPi4B's and AP mode. It can be very stable but a lot of trial and error can be required depending on what you are doing but I think you already know this.

@TrylobitBroccoli

The things that experience has taught me:

• The USB subsystem on RasPi's has an almost infinite amount of problems that it can share with us.
• How many things are plugged into USB ports?
• How much power do they pull? (The RasPi4B subsystem has a limit of 1200 mA of power)
• Are you using a powered hub? If so, which one is it? (powered hubs on RasPi's is a legendary problem)
• In stressful situations, it might be good to turn off Scatter-Gather for your adapters as @Thimbles809 mentioned.

I see you are trying to set up a WiFi client feeding an AP. That can be a challenge because basic networking does not want you to do that (and for good reason). I'd be interested to know what guide you are following so I could experiment with a setup like this and maybe add some info to my guide.

@morrownr

[TrylobitBroccoli]

• The only things plugged into USB ports are the WiFi adapters.
• They should pull max. 800mA together.
• I'm not using a powered hub.
• I have turned off Scatter-Gather.

On Raspberry Pi forum they suggested I should by the official PSU as it has very tight power delivery that most USB chargers don't have. So I'm going to buy that, make new installation and make notes along way to demonstrate exactly what I'm doing.

"That can be a challenge because basic networking does not want you to do that (and for good reason)."
What's the reason? Why is that a bad idea? I thought that is the idea behind having a travel router.

[morrownr]

On Raspberry Pi forum they suggested I should by the official PSU as it has very tight power delivery that most USB chargers don't have. So I'm going to buy that, make new installation and make notes along way to demonstrate exactly what I'm doing.

A solid power supply is vital for this setup so you appear to be headed in the right direction.

"That can be a challenge because basic networking does not want you to do that (and for good reason)." What's the reason? Why is that a bad idea? I thought that is the idea behind having a travel router.

Let me see what you are doing before I answer.

[TrylobitBroccoli]

OK. Here is what I've just done:

1. Followed this video to install OpenWRT and get a full microSD cards capacity for the OS.
   https://www.youtube.com/watch?v=_pBf2hGqXL8&t
   Except for the installation of the USB ethernet adapter.
2. At this moment I installed kmod-mt76x2u in OpenWRT.
3. I’ve added a file:
   cat /etc/modules.d/mymoduleparam.conf
   mt76-usb disable_usb_sg=1
4. Plugged in just one USB Adapter.
5. Created a Wireless AP and added it to LAN interface, change device to wlan0, enabled DHCP on the interface and disconnected the ethernet cable.
6. Connected back to RPi via new WiFi AP.
7. Changed DHCP setting to not collide with my home network.
8. Created a WAN interface on eth0 and connected back the ethernet cable.
9. Time for speed test. Run 3 times. Results 400-480Mbps up and down (1Gbps internet connection, so that is not a limiting factor). Also made a 20GB transfer from my NAS to stress test. No speed dumps and no freezes. As far as quick testing goes, I can say that the router is stable.
10. Here comes first weird thing: I can’t change the channel of AP to anything but 36. If I try to change it to anything else (tried 52,60 and 100):
    Radio1: Device is not active
    SSID: Wireless is not associated
    LAN Interface: Error: Network device not present.
11. I’ve plugged in 2nd WiFi adapter. Scanned for my home network and it connected to it. What is interesting is that my home network is on channel 60, which with the other adapter I wasn’t able to operator on in AP mode. Created new interface called WWAN, assigned to wan firewall zone and disconnected ethernet cable. Now I should have WiFi-WiFi bridge.
12. Time for speed test. Initially it’s going great 237Mbps down, but then suddenly it freezes, takes a while to load upload test, but then comes back. Upload test comes in only with 58Mbps.
    Speed test 2: 285/65 a bit better. I’m impressed it hasn’t crashed yet… But the upload speed is very disappointing. I’m usually backing up big video files when I travel.
    Speed test 3: 177/66. To be honest I will be happy if I get stable 150 up and down.
    Just as I was about to do a 20GB transfer stress test the AP network is gone. The RPi is up. I managed to log in via my home network. Maybe it is a power issue in the end?

I will get the original Raspberry Pi PSU Thursday so I'll test it then.
Why do you think I can't change AP channel tho? This shouldn't be connected with PSU...

[morrownr]

Here comes first weird thing: I can’t change the channel of AP to anything but 36. If I try to change it to anything else (tried 52,60 and 100):
Radio1: Device is not active
SSID: Wireless is not associated
LAN Interface: Error: Network device not present.

On 5 GHz, there are regular channels and DFS channels. The channels that fall into each category depend on your country.

The mt7612u driver does not support DFS channels for AP mode. It supports DFS channel for managed mode just fine.

In my country, 36 is a regular channel but 52, 60 and 100 are DFS channels. We also have 149 as a regular channel.

Just as I was about to do a 20GB transfer stress test the AP network is gone. The RPi is up. I managed to log in via my home network. Maybe it is a power issue in the end?

It very well could be a power issue. I've learned with Pi's that trial and error are the only way to make things stable.

USB3 is a little more problematic than USB2 and always has been. You said stable 150 Mb/s up and down. That is possible with USB2 so you might test with the adapters using the USB2 ports.

[TrylobitBroccoli]

I've got the official PSU. Still no joy on USB3. WiFi to WiFi bridge fails a speed test (usually first speed test, sometimes I manage to run the 2nd, but it crashes on the 2nd).
Usually one of the WiFI adapters crashes as I am able to ssh into RPi via the home network.

On USB2 everything works well, I'm managing to do as many speed tests as I want. It also manages to finish my 20GB local transfer test.
Unfortunately I'm getting only 50Mbps...

Any ideas how to proceed to make it work on UBS3?

[bjlockie]

I used wired to my home network with a ethernet to USB3 dongle and a AWUS036ACM on 5ghz for my AP. I guess I lucked out with the powered USB 3 hub hub. I also compiled my own openwrt since it was before the raspberry pi4 was officially supported. Did you verify scatter gather stays off after a reboot? Would you be able to try only one AWUS036ACM? Or maybe 2 but on different bands.

[TrylobitBroccoli]

• Yes, the Scatter Gather is off:
  root@OpenWrt:~# cat /sys/module/mt76_usb/parameters/disable_usb_sg Y

• Everything works great with just one AWUS036ACM.

• For some reason, I can't put them in 2.4GHz mode...

[amisix]

I ran almost your exact setup as my primary router for quite a while. I'm able to run dual ACMs (on USB3) without a powered hub although I put one in because I added an additional USB gigabit ethernet adapter. JEAXIN makes a great 4 port powered hub that uses micro USB as its power input.

Just out of left field, the Pi isn't throttling itself for any reason is it (undervoltage/thermal)? Check after boot and after crash. Anything other than 0x0 means it is.

vcgencmd get_throttled

[TrylobitBroccoli]

I didn't change any voltage changes or overclocking. It has a radiator with fans (https://botland.com.pl/obudowy-do-raspberry-pi-4b/16012-obudowa-justpi-do-raspberry-pi-4b-aluminiowa-z-dwoma-wentylatorami-szara-5903351242646.html)
So I don't think it's throttling. I bought the RPi used. It was used with a 3D printer before, so I don't think it should be worn.

After booting: throttled=0x0
After crash: throttled=0x0

[bjlockie]

Also make sure the firmware is updated too. You might need to use RaspbianOS. sudo rpi-update to run the utility,

[TrylobitBroccoli]

I have a separate SD card with RaspbianOS just to make the updates. All of the firmware is up to date.

[TrylobitBroccoli]

New idea: I get a router that can run OpenWRT and has a capable USB 3.0 port that will allow me to plug in one AWUS036ACM.
What do you think? Is there a small router that meets these criteria?

[bjlockie]

Good idea. I would browse the openwrt forums to find a cheap router.

[morrownr]

That is a good idea.

I've used the OpenWRT forums for years to figure out what wifi routers to buy and it works well. If you will check your local sources for routers in your price range and post a list here, I'll do some recon at OpenWRT and offer some recommendations.

I don't hang around there to see what works. I do it to find out what works really really good.

My main router these days is a ZyXEL NBG6817 (Armor Z2). I don't think it is still for sale but wow, it is good and works so well with OpenWRT. It has two USB ports. One is a USB3 port and the other is USB2. My ACM lived in the USB3 port for a long time and wll eventually find its way back there when I am finishing doing some testing. I use the ACM on channel 36 as that is the least congested non-DFS channel in this area and I need something non-DFS as I have a couple of household IoT things that won't do DFS. The internal 5 GHz radio is on channel 116 DFS as that is what I use for my LAN. It is Wave2 and is FAST! This setup with 3 radios works well. Extremely stable.

@morrownr

[TrylobitBroccoli]

It's supposed to be a travel router, so I'm not looking to spend tone of money. I'm expecting to get stable 150Mbps wireless and be OK for 6-7 devices.
I found 2 cheap and relatively small routers, both have USB 3.0:
Linksys EA6350 V4
Linksys EA7300

Do you have any experience with any of them?

[morrownr]

@TrylobitBroccoli

Do you have links to the Linksys routers you are talking about?

It's supposed to be a travel router...

A travel router in this day in time is generally something that is small, hard to damage and can fit in a small pouch. It takes a wifi signal in and provides both a wifi signal out and a ethernet port out. It can also provide additional capabilities like vpn, etc.

Generally it needs to provide 100-200 Mbps. There is no need for more in most cases and that is pretty fast. It does not need long range since you will usually be close to the router.

Given the above, a RasPi4B in a nice solid case should work well and is flexible. If you have a good power and one wifi adapter that can support the above, it is a matter of setting it up like you want. I would not use an Alfa ACM is it is a big adapter with multiple antennas and has more speed than you really need. A single antenna adapter with a mt7610u chipset to receive should work well and using the Pi internal 5 GHz for transmitting signal should work for this situation. If you want to investigate this, I can find and forward a guide dpending on whether you want to use the RasPiOS or OpenWRT.

@morrownr

[TrylobitBroccoli]

Here are links to the routers I mentioned:
https://openwrt.org/toh/linksys/ea6350_v4
https://openwrt.org/toh/linksys/ea7300_v2

Given the above, a RasPi4B in a nice solid case should work well and is flexible. If you have a good power and one wifi adapter that can support the above, it is a matter of setting it up like you want. I would not use an Alfa ACM is it is a big adapter with multiple antennas and has more speed than you really need. A single antenna adapter with a mt7610u chipset to receive should work well and using the Pi internal 5 GHz for transmitting signal should work for this situation. If you want to investigate this, I can find and forward a guide dpending on whether you want to use the RasPiOS or OpenWRT.

I have the original Raspberry Pi PSU.
I already own 2 Alfa ACM adapters, so it would be great to use them.
As you mentioned it should handle 100-200Mbps, accordingly to my testing Pi internal 5GHz can't handle that. I'm lucky if I can get 80Mbps, that's why I wanted to use two Alfa adapters. I wanted to use OpenWRT as I used it once before, but if using RasPiOS will allow to use 2 Alfa adapters I will happily go for it.

[morrownr]

I looked at the two routers you mentioned. It might be a good idea to continue the search. I think you can do better. Disclaimer: I am not fan of Linksys.

Something like this?

https://www.amazon.com/GL-iNet-GL-A1300-Encrypted-Tethering-Pocket-Sized/dp/B0B4ZSR2PX

List of OpenWRT supported adapters by the same maker:

https://openwrt.org/toh/views/toh_fwdownload?dataflt%5B0%5D=supported+current+rel_%3D22.03.3&dataflt%5BBrand*%7E%5D=GL.iNet

Recommend you stick to Qualcomm/Atheros or Mediatek chipsets.

We can still look at a RasPiOS solution if you are interested. I've been thinking about making a new guide for what is basically a travel router.

@morrownr

[TrylobitBroccoli]

I was thinking about GL-iNet, but there are quite a lot of people raising concerns about security, so I'd consider only a model that can be flashed with vanilla OpenWRT, the GL-A1300 seems not to be supported. It's not on that list.

We can still look at a RasPiOS solution if you are interested. I've been thinking about making a new guide for what is basically a travel router.

Would using RasPiOS solve the USB 3.0 problem?

[morrownr]

I'd consider only a model that can be flashed with vanilla OpenWRT...

Yes, absolutely. I guess I should have said that.

the GL-A1300 seems not to be supported. It's not on that list.

It is not on the list yet. Will it be at some point? Probably but there is no way to know. It uses the same chips as a couple of routers that are supported so my best guess is that it is a matter of someone taking on the task. That specific model appears to be fairly new to the market.

This is just something that you need to research to make sure you know what you are getting. My best guess is that you would be happier with something like this rather than the Linksys models.

Would using RasPiOS solve the USB 3.0 problem?

Not necessarily. There are two things about the RasPi4B that I really hope that is improved in the next Pi.

• Bump the amount of power available in the USB subsystem up to specs.
• Get a better USB3 supporting chipset.

Somewhere up there in one of your previous messages you say that with the cards connected to USB2, everything works. Well, that is my experience as well when using multiple usb wifi adapters on a Pi4B. It does not matter if you mix and match adapters, drivers and chipsets. I have many adapters and have tested many combinations. With a Pi4B, you have to fiddle around until you find what is stable. Unless you need more than one usb wifi adapter in USB3 ports, stay away from it (Pi4B only). My opinion is that you can get the capability you want, around 150 Mbps, using only USB2 ports. This is in theory only.

Now, I know you said things were slow but you need to understand that the hardware, the adapters along with their supporting drivers can only do so much. Ultimately what throughput you get is also determined by the congestion on the channels in use in the area where you are going to use them. Please understand that WiFi is designed to be a shared technology. Anytime you have your device on a channel where there are other AP's on the same channel, there is sharing on the available bandwidth going on. In looking back at the messages where you posted your throughput, I see the probability in several cases where the low throughput was probably due to congestion. You can't win that battle unless you control all wifi ap's in your area so you have to come up with a plan based on good knowledge of how wifi works. If you look at the wifi speed test I have on the Main Menu, you will see some high numbers. That is due to me using my knowledge to maximize the capability and air that I have available to me. My LAN runs on a DFS channel and it smokes. On the other hand, some devices can't use DFS channels and some devices can't use 5 GHZ so I have 3 radio's going:

• channel 11, 2.4 GHz, least congested channel in the band and it works well.
• channel 36, 5 GHz, least congested of the 2 non-DFS channels available and it only handles devices that can't do DFS like Roku.
• Channel 116, 5 GHz, DFS, I am the only user on the channel, period. My LAN can run full speed at Wave 2.

My wifi usage in home works very well. Family never complains.

Now, for a travel router where you will not control the wifi situation, you should not expect optimal results. You may never get even close to 150 Mbps and it is not the fault of your equipment. I can go through all of the reasons why this is unlikely if you want. If it were me, I would lower my expectations and just concentrate on flexibilty and mobility. Unless you are in a hurry, just keep an eye on the brand of travel routers we discussed and use your time for now to work with me to learn about wifi while we both use a RasPi4B, RasPiOS, one Alfa ACM, and a good power supply to build a guide and solid, yet flexible "travel router." Are you up for it?

@morrownr

[TrylobitBroccoli]

the GL-A1300 seems not to be supported. It's not on that list.

It is not on the list yet. Will it be at some point? Probably but there is no way to know. It uses the same chips as a couple of routers that are supported so my best guess is that it is a matter of someone taking on the task. That specific model appears to be fairly new to the market

I was actually ready to buy one of them, but then after doing some online research I found at least 4 people concerned about security.
To be honest, if I had enough skill I would take the task to flash it with vanilla OpenWRT. I'm even willing to buy it if there is someone that would like to cooperate with me to do it and then upload the instructions and image to OpenWRT.

Somewhere up there in one of your previous messages you say that with the cards connected to USB2, everything works.

Yes, but it's very slow, I don't remember exactly, but I think I was getting 20-50Mbps, so kinda pointless.

Now, I know you said things were slow but you need to understand that the hardware, the adapters along with their supporting drivers can only do so much. Ultimately what throughput you get is also determined by the congestion on the channels in use in the area where you are going to use them. Please understand that WiFi is designed to be a shared technology.

I totally get that. I'm not sure why you have the impression that I demand perfect throughputs. I feel like I'm not asking too much. If the single Alfa adapter is getting up to 500Mbps - real world, my own testing - I don't think me asking 150Mbps of WiFi to WiFi bridge is too much. And I'm getting that and even more - that is until the Raspberry Pi crashes :). So I understand network congestion and channels. At my home, I have a Ubiquiti network with WiFi6 APs that I configured myself, so I have a basic understanding. I'm not a specialist, but I think I can qualify myself in a "prosumer" category.

Now, for a travel router where you will not control the wifi situation, you should not expect optimal results. You may never get even close to 150 Mbps and it is not the fault of your equipment.

I get that. I'm not even mentioning this subject. Of course, it depends mainly on 1. what I'm going to get at a location I will use it and 2. if I will find channel that will be free enough.

Unless you are in a hurry, just keep an eye on the brand of travel routers we discussed and use your time, for now, to work with me to learn about wifi while we both use a RasPi4B, RasPiOS, one Alfa ACM, and a good power supply to build a guide and solid, yet flexible "travel router." Are you up for it?

I have it set up right now like that. No problem, but as I'm not happy with Raspberry Pi built-in WiFi I will use it only if I get an ethernet connection (which happens from time to time).

I don't know if you are up for it, but if you want to do a co-op I can buy GL-A1300.

[morrownr]

It has been a long time since the internal wifi on my RasPi4B has seen the light of day so I thought I would do a little testing. In managed mode, I could get around 60 Mbps on channel 11. That channel is very lightly congested. I could get around 130 Mbps on channel 60 (DFS, no other APs) for 5 GHz. Then I decided to do a comparison first with the Alfa ACM:

$ iperf3 -c 192.168.1.1
Connecting to host 192.168.1.1, port 5201
[  5] local 192.168.1.228 port 41222 connected to 192.168.1.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  50.1 MBytes   420 Mbits/sec    0    798 KBytes       
[  5]   1.00-2.00   sec  46.2 MBytes   388 Mbits/sec    6    322 KBytes       
[  5]   2.00-3.00   sec  47.5 MBytes   398 Mbits/sec    0    423 KBytes       
[  5]   3.00-4.00   sec  47.5 MBytes   399 Mbits/sec    0    502 KBytes       
[  5]   4.00-5.00   sec  48.8 MBytes   409 Mbits/sec    0    568 KBytes       
[  5]   5.00-6.00   sec  47.5 MBytes   398 Mbits/sec    2    440 KBytes       
[  5]   6.00-7.00   sec  47.5 MBytes   399 Mbits/sec    0    518 KBytes       
[  5]   7.00-8.00   sec  42.5 MBytes   357 Mbits/sec    2    397 KBytes       
[  5]   8.00-9.00   sec  46.2 MBytes   388 Mbits/sec    2    375 KBytes       
[  5]   9.00-10.00  sec  47.5 MBytes   398 Mbits/sec    0    462 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   471 MBytes   395 Mbits/sec   12             sender
[  5]   0.00-10.01  sec   469 MBytes   393 Mbits/sec                  receiver

iperf Done.

And then with my CF-951AX with a mt7921au chipset and RasPiOS upgraded to kernel 6.1 with the latest mt7921 firmware. It showed an average of just under 650 Mbps. It is wave 2 capable and so is the router so, of course, it was smoking!

So, no need to press on to AP mode with the RasPi internal wifi. Broadcom is near the bottom of my preferred wifi chipset list but I wanted to see for myself. I know, you told me so.

It is not clear to me why the problem with 2 ACM's. Do you have any other usb wifi adapters that could be tested?

I don't know if you are up for it, but if you want to do a co-op I can buy GL-A1300.

That is something I may be interested in. I can't do it right now as I am in the process of moving. Maybe in a couple of months we could look at this. All indications are that it would not be that difficult. Many current wifi 6 routers are a challenge to get OpenWRT going as some of the makers are locking them down with secure boot and it can take time to jailbreak.

[TrylobitBroccoli]

It is not clear to me why the problem with 2 ACM's. Do you have any other usb wifi adapters that could be tested?

I have one somewhere in storage. It's going to be a challenge to dig it out.

That is something I may be interested in.

Awesome. Next month or so is going to be busy for me too, but we can connect and work on it let's say 2nd part of April?
Maybe we will need to connect on some other platform for quicker communication.