WiFi signal is very noisy when HDMI is plugged in

VIM3
1

This is on a VIM3 pro running a custom image. We are seeing extremely noisy WiFi signals when the HDMI cable is plugged in.

Note that the following is for a 2.4GHz connection because we are constrained to use this frequency.

For example, HDMI plugged in:

RSSI: -71 dBm SNR: 16 dB  noise: -85 dBm

Without HDMI plugged in:

RSSI: -64 dBm SNR: 29 dB  noise: -91 dBm

We’ve tried with an headless HDMI dongle and are seeing similar results.

The next step is to try an HDMI cable with better shielding but curious if others are seeing similar issues and if there are firmware or other workarounds for this problem.

Thanks.

2

Hello @amitu

Thanks for your feedback, we will try to reproduce this issue on our side. and we will followup this issue with email.

We have a few questions need to confirm:

  • Does your board have the Wi-Fi antenna attached?
  • Does your board have the heatsink installed?

Thanks.

3

Thanks for the quick response.

Yes, the board has a heatsink.

Yes, we have the IPEX antenna plugged in (see attached image)

image
image844×588 60 KB

4

Hello @amitu

We have just checked on our side with the Android image on VIM3. There is no difference for the Wi-Fi signal whether HDMI cable is attached or not.

  • HDMI Attached: -63dBm
  • HDMI not attached: -65dBm

HDMI Attached:

image
image1920×1097 117 KB

HDMI not attached

image
image1668×1348 140 KB

Have you checked other HDMI cable? Or other system?

5

Thanks for testing and providing the results.

Could you also provide the link to the image you are using? We will re-run the test using the same image on our side.

7

Hello @amitu

You can try this Android on your side.

https://dl.khadas.com/products/vim3/firmware/android/vim3-android-9-64bit-v231122.img.xz

8

Hi @numbqq , I work with @amitu and tested out the image you recommended above. I see a very high noise reading from wlan (and just to clarify the RSSI reading is ok but the noise is causing a lot of interference in some instances). I used the wl tool from Synaptics and that shows the high noise value. For example,

kvim3:/data # ./wl status                                                                                                                                                                                                                     
SSID: <redacted>
Mode: Managed	RSSI: -59 dBm	SNR: 19 dB	noise: -76 dBm	Flags: FromBcn RSSI on-channel 	Channel: 9
BSSID: 58:11:22:5A:1A:40	Capability: ESS WEP ShortSlot RRM 
Supported Rates: [ 1(b) 2(b) 5.5(b) 6 9 11(b) 12 18 24 36 48 54 ]
RSN (WPA2):
	multicast cipher: AES-CCMP
	unicast ciphers(1): AES-CCMP 
	AKM Suites(1): WPA2-PSK 
	Capabilities(0x000c): No Pre-Auth, No MFPR, No MFPC, Pairwise, 16 PTK Replay Ctrs1 GTK Replay Ctr
Extended Capabilities: IW 20/40_Bss_Coexist BSS_Transition
VHT Capable:
	Chanspec: 2.4GHz channel 9 20MHz (0x1009)
	Primary channel: 9
	HT Capabilities: SGI20 SGI40 
	Supported HT MCS : 0-15
	Supported VHT MCS:
		NSS1 Tx: 0-9   Rx: 0-9 
		NSS2 Tx: 0-9   Rx: 0-9 
		NSS3 Tx: 0-9   Rx: 0-9 
		NSS4 Tx: 0-9   Rx: 0-9 
WPS: V1.0 Configured
VS_IE:dd180050f204104a00011010440001021049000600372a000120
VS_IE:dd31f832e4010101020100031435f4ca9714a698a8c83f04b68e4ed7de5aed3b8d07045aed3b8d120440440048130101150100
VS_IE:dd1a00904c0418bf0cb169830faaff0000aaff0020c0050009000000
VS_IE:dd090010180209009c0000
VS_IE:dd180050f2020101840003a4000027a4000042435e0062322f00

You can see that the noise is -76 dBm whereas the usual reading is -91 dBm.