Can not receive any data from TX

[iamfaith]

Hello, thanks for making such an amazing project.

But I face some problems while using this.

Hardware:

gs as a Linux virtual machine with TPLink TL-WN722N V1.

It can be set into monitor mode like the following picture:

start with:

drone as raspberry pi zero with Linux Kernal patch, which can be set into monitor mode also.

start with: ./wfb_tx -p 1 -u 5600 -K drone.key wlan0

Problem:

I print some logs at the file of rx.cpp at line 688 like this:

But the rc value is always 0.

How could I solve this problem? I can verify that the GStreamer works well because I can forward the video stream from Pi zero to my PC via standard wifi.

[iamfaith]

BTW, when I enable DEBUG_TX, my PC can receive the UDP packets from Pi Zero. But fail for PcapTransmitter.

[iamfaith]

the command I used:
TX: ./wfb_tx -p 3 -u 5600 -K drone.key -S 1 -L 1 -B 20 wlan0
RX: ./wfb.rx -c 10.0.2.15 -p3 -u 5600 -K gs.key $rx

[svpcom]

1. Is it ath9k? If yes, you need to upload custom firmware https://github.com/OpenHD/Open.HD/tree/master/firmware/AR9271
2. DEBUG_TX used for FEC testing only - it doesn't inject packets to cards, but send it as UDP packets to 127.0.0.1:5601
3. what is $rx? Do you run these commands on the same host or on the different?

[svpcom]

I don't recommend ath9k - use rt28xx or rtl8812au instead

[iamfaith]

For the drone side, I use the re4son patch on my raspberry pi zero which can enable monitor mode. So I just use internal wifi card for raspberry pi zero.

For the gs side, I use this wifi adapter.

the $rx is just the variable of my wifi interface.

[svpcom]

Without firmware patch ath9k will unable to switch radio channel. See #46 (comment)
I'll suggest to use patched ath9k on drone (as TX) and internal raspberry pi card as RX. But I highly recommend to use rtl8812au and/or rt28xx instead of them

[iamfaith]

I did not apply any patch on ath9k, but it can switch the channel?

Because pi zero is very small then I would like to put it on the drone. And use my laptop as RX on the ground. I would like to use the internal wifi card of pi Zero rather than external card, which can reduce the weight.

[svpcom]

Are you sure, that internal zero card can do packet injection?

[svpcom]

monitor mode != packet injection in general case

[iamfaith]

monitor mode != packet injection in general case

Thanks for your clarification. But do I check it supports injection or not? I was thinking monitor mode == packet injection originally.

[iamfaith]

But actually, I add some logs here. It will never throw out the runtime error. I think it should support packet injection.

I need to find some way to install the patch on my RX wifi card.

[iamfaith]

Without firmware patch ath9k will unable to switch radio channel. See #46 (comment)
I'll suggest to use patched ath9k on drone (as TX) and internal raspberry pi card as RX. But I highly recommend to use rtl8812au and/or rt28xx instead of them

If I use rtl8812au for the ground side, do I need to patch rtl8812au? Or it just supports the monitor mode.

[svpcom]

1. monitor_mode == allow to capture packets. Not all cards support that (but much more than support injection)
2. If card doesn't support injection it can silently ignore it and doesn't return any errors. Only a few wifi cards supports injection (ath9k with patches, rt28xx out of box, rtl8812au with patches, some builtin broadcom cards in RPI with custom firmware and patches)
3. In case of rtl8812au patch is only needed for injection. it already supports monitor mode

[svpcom]

ath9k without patches inject packets but ignore wifi channel and modulation type (MCS) settings. So RX card will listen one channel and TX transmit on other.

[iamfaith]

Well explained. I have tried on one channel. But it still doesn't work. I think you are right. My Pi zero internal wifi card doesn't support packet injection.

Maybe I need to buy an RTL8812AU wifi adapter for my Pi Zero.

I just notice another wonderful project from you: https://github.com/svpcom/rtl8812au

Can I use sudo ./dkms-install.sh to install this patch on any Linux OS?

Thanks

[iamfaith]

Yes. rt28xx card work in injection/monitoring modes out of box.
I don't know what packets aireplay-ng injects into wifi. Need to read its manual

Thanks for your reply. is it the same for rtl8812au with injection/monitoring modes out of box

[svpcom]

No. For rtl8812au you should use https://github.com/svpcom/rtl8812au driver. Stock driver doesn't support injection.

[iamfaith]

No. For rtl8812au you should use https://github.com/svpcom/rtl8812au driver. Stock driver doesn't support injection.

OOOOh, thanks. The stock driver of rtl8812au only supports monitor mode. right? If used this ground side, it doesn't need this driver. But for the drone side, need to use https://github.com/svpcom/rtl8812au driver, is this correct?

[svpcom]

If you want to use only one-side communication (like video only), you can use it. But ip tunnel will not work

[iamfaith]

Yes, what do you mean by ip tunnel? Is it for mavlink telemetry

[svpcom]

https://github.com/svpcom/wifibroadcast/wiki/Setup-HOWTO
Out of box WFB provide 3 channels:

1. Video downstream
2. Bidirectional mavlink
3. IP tunnel

In case of unidirectional communication will work only (1) and (2) in downstream mode. (3) will not work at all

[iamfaith]

Thanks, I see this! Is it based on UDP? It can be used to send commands to Drone.

BTW, is it possible to disable encryption on the video tunnel which may reduce latency? Or can it be as a switch in the configuration file?

[iamfaith]

Dear svpcom,

Do you suggest using RTL 3070 or RTL 5370 wifi cards?

[svpcom]

Both should work, but I used only RT5572 and RT3572

[svpcom]

Encryption doesn't affect to latency. it is always on. If you don't need it you can try to use https://github.com/OpenHD/Open.HD. They have premade images

[iamfaith]

Both should work, but I used only RT5572 and RT3572

Thanks. Do they support injection mode out of the box? How can I check that before I buy it?

[svpcom]

RT5572 and RT3572 supported by rt28xx without any patches. But these chipsets are out-of-stock now.
They works for me, but I'm unable to guarantee that they will work in all cases. Packets injection and monitor modes are not officially supported by any chipset. For new setups I'll recommend to use rtl8812au (not "bu" or other models)

Both should work, but I used only RT5572 and RT3572

Thanks. Do they support injection mode out of the box? How can I check that before I buy it?

[iamfaith]

Thanks. Why do you recommend rtl8812au? It's a little bit expensive compare with rt28xx in my country. But in my country, I can still buy rt28xx chipsets.

I just find that TX power is only 20 dBm. Is there any way to maximize it?

You help me a lot.

Realllly appreciate a lot

[iamfaith]

In contrast, my raspberry pi zero has 31 dBm in TX power which higher than my rt28xx wifi card.

[svpcom]

This is a fake TX power. 31dBm is ~ 1W of output. Only card with heatsink can operate. Some of rtl8812au can output such power, for example https://www.aliexpress.com/item/4001243968808.html, but heatsink (or active cooling) is required