Pi5 WiFi or HDMI - not both

Help and Support
1

I am fairly certain that I’ve read - inside a topic here somewhere - of someone who had trouble with a pi5 - either joining the WiFi but not allowing the connection of an HDMI monitor or allowing the monitor connection and falling back to the hotspot.
I’ve searched but cannot find the topic involved.

I have the same problem, although if I’m really lucky I might just get both WiFi and hdmi, but not very often.

Plugging the monitor into the pi after boot up seems to get past this problem but is not really a feasible solution.
Could this be a fault with my new pi5?
I’m using the official 45w pi supply and have tried three different monitors / leads / adapters.
Any pointers to the relevant topic, or if someone has had the same problems……
Many thanks in advance.

2

Hey @Old_Duffer,

This sounds like RF interference between the HDMI cable and the Pi’s WiFi antenna - a known issue on Raspberry Pi boards with onboard WiFi.

Important note on documentation: Most detailed analysis of this problem was done on Pi 4, but the same behavior has been reported on Pi 5:

This thread describes identical symptoms to yours on Pi 5 - WiFi drops when HDMI display is connected, reconnects when disconnected.

Why Pi 4 documentation applies to Pi 5:

  • Both use Broadcom CYW43455 WiFi chip (same silicon)
  • Both use PCB trace antenna in similar board location relative to HDMI ports
  • Both use micro HDMI connectors
  • The interference mechanism is physics-based (RF emission from HDMI signals), not software or firmware specific

Pi 4 references with detailed testing data:

Your observation that plugging the monitor in after boot sometimes works is consistent with this - WiFi establishes connection before interference begins and can sometimes maintain a degraded link.

To investigate your specific situation, please provide:

  1. HDMI cable brand/type and length
  2. Are you using an adapter (micro HDMI to full HDMI) or direct cable?
  3. Which HDMI port on the Pi5?
  4. WiFi band - 2.4GHz or 5GHz network?
  5. Is the Pi5 in a case? If so, which one?

Potential solutions (proven on Pi 4, expected to apply to Pi 5):

  • Use a triple-shielded HDMI cable (official Raspberry Pi micro HDMI cables are designed for this)
  • Avoid adapters - use a direct micro HDMI to HDMI cable
  • Try HDMI port 1 instead of port 0
  • Add ferrite chokes on the HDMI cable close to the Pi
  • Keep cable length to 1m or less
  • Try switching WiFi bands if your router supports both

To confirm this is the cause: boot without HDMI connected, verify WiFi connects, then plug in HDMI and check if connection drops.

Kind Regards,

3

Thank you for your time and expertise.
I realise, reading your reply, that I should have delved more into the raspberry pi side of things rather than Volumio (I rarely use a pi for anything else these days).

Pi is not in a case.
Will try HDMI 1 and changing WiFi bands.
Leads have all been shorter than 1m.

As to the make of leads, :person_shrugging: - lots in a box - will try them all whilst waiting for a decent, ‘non-adaptered’ lead to arrive.
Will report back as and when.

Many thanks once again….