Saturday, May 16, 2015

HDMI cables are NOT all the same!

Sometimes very cheap or thin HDMI cables do not work with the Raspberry Pi Camera extension kit I made. Even if a camera is correctly plugged at startup, the Rpi cannot detect the camera and output an error message. In this short post I will explain why and show a quick fix.

First a normal HDMI cable with 19 lines. This is the most common design. There are four data buses (one is hidden behind in the pictures) with 3 cables in each, a GND line and a GND shield. The HDMI connectors are also put to GND. The Raspberry Pi Camera extension kit works with this kind of cable.


Now, this is a smaller diameter (it was Micro HDMI before I cut it) cable with only 15 threads. This cable has 5 data shields but there are no GND lines in them! There is not GND shield, just a wrapping that was cut before taking the picture. The HDMI connectors are put to GND. This cable does not work out of the box with the Raspberry Pi Camera extension kit.

The trick to make the second cable work with the kit is to connect with a short piece of wire and solder the GND on the PCB and the HDMI connector. Of course this must be done on both sides of the cable. Et voila!
Even if there are no data shields, the quality of the image from the camera does not seem to be affected.



 If at this stage if there is no image from the camera it is time to ask me an exchange.

Note that I could have connected the HDMI connector to GND by default, I decided against this. For safety reason I try to avoid connected metallic parts floating around.  

22 comments:

  1. Does this modification need to e done to both connectors (ie the camera end and the Raspberry Pi end)?

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    Replies
    1. Yes on both connectors to connect their ground pins.

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  2. Hi, great product. Just wondered if there was an enclosure for the rpi with twin hdmi ports?
    cheers
    Phil

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  3. I still can't get mine to work. I've got three different HDMI leads and brought three pairs of the HDMI extenders. Testing with a multimeter it appears that connector 14 on the ribbon cable (SDA0) is not connected at the other end. Any tips?

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  4. I tried this, but it turns out in my HDMI leads even the metal plug cases are not connected!
    I had CSI pins 1,4,7,10 (Grounds) and 14 (I2C data) unconnected.
    My fix is detailed at https://www.john.geek.nz/2015/07/petit-studio-raspberry-pi-hdmi-extender-cheap-cable-fix/

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    Replies
    1. Awesome and fun writeup on that page. Recommend for anyone working with these to go read John's work on the cables.

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  5. Did anyone succeed using a 'cheap' 5m *flat-styled* HDMI cable? If so, which one? A short round cable (1.5m) works properly, but the 5m of http://www.aliexpress.com/snapshot/6933422178.html does not work, even after re-routing pin 14 to signal path to pin 'A' (because 14 was not connected). Shielding & all relevant pins are properly connected with this mod, but signal integrity seems insufficient (led on camera remains on though). Ferrite cores don't make any difference...
    I really could use a working 5m (white) HDMI cable, preferably flat(!), so it would be great to have some reference of any success stories.

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  6. Great to have a link to good cables as well

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  7. If HDMI cables costs a few more dollars it doesn't matter as along as they work properly i have seen couple of good hdmi cables at cheaper price HDMI Cable NT

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  8. yes by looking at the clarity of the screen we get to know the HDMI Cable quality whether it's good or best and now a days we can find cheap quality cables at cheap prices under any online websites like <a href="http://latestone.com/>latestone</a> still better to have proper warranty attached

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  9. I am in Kolkata, India, where even a good quality HDMI cable is rare. I got your extension boards and tried three different HDMI cables. None worked. I tried to check continuity and found pins 13 and 14 shows open through the HDMI cable. Can you share the Name of a working Cable, so that I can order that from ebay or amazon. Thanks

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  10. It would be awesome to have a list of HDMI cables that work, or some kind of identifier for the good ones. Thanks!

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  11. My Experience with some eBay HDMI Cables...
    This one works fine ... http://www.ebay.de/itm/251772881370
    And this is a Trouble cable ... http://www.ebay.de/itm/141346673708

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  13. Hello, I followed above blogpost as my camera wasnt working with HDMI cable. Still I face following issue..
    mmal: No data received from sensor. Check all connections, including the Sunny one on the camera board
    ..I used jumperwire for now to connect the ground

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