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  • Author Author: ralphjy
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SparkX - SparkFun Experimental Products

ralphjy

I recently accidentally discovered a part of SparkFun that I hadn't encountered before - SparkX, their line of experimental products.

 

I purchased a MicroMod Big Display Carrier Board https://www.sparkfun.com/products/17718  to try out bitbanged DVI using the RP2040 RP2040 HDMI Display and didn't notice that I was buying a SparkX product.  The big giveaway is that the PCB color is black rather than the red of their standard products.  And it is clearly labeled.

 

I've had some issue getting my monitors to recognize this board as an HDMI source.  A comment from Luke Wren caused me to look at the schematic and realize that there is a schematic error that causes the board not to properly source 5V to the monitor.  It looks like they were expecting the 5V to come FROM the monitor.

image

 

I posted on the SparkFun forum and also raised an issue on their github page, but I noticed that my forum post got moved and also didn't get any responses.  It finally occurred to me that this was not a standard product image.  Must be due to pandemic induced brain fog....

 

image

 

I actually like the idea of getting to try new things quickly, just didn't realize that this was an experimental product.  I'll have to get out the DMM and verify which component is D5.  The simplest fix is to short it out, but I probably should remove the component.  The minimum spec for the HDMI 5V is 4.8V, but I think it should work if I leave D3 and the fuse in the path.  I'll have to measure the voltage...

 

I'm sure I'll buy SparkX products in the future.  I'll just expect that they may require additional effort.

 

EDIT 3/19/21:  I received a response on github.  See below.

image

 

The referenced link is https://www.ti.com/lit/an/snva412c/snva412c.pdf?ts=1615898507918 .  Which includes a condition where two HDMI sources might be connected together (although it does use the word "accidentally").

 

So, SparkFun did intend to power this board over the HDMI 5V line.  I was not aware of that capability in monitors or TVs, but apparently they are aware of use cases.  So, the modification that I had suggested would be a bad idea if there were another source trying to drive the 5V line.  And shorting out D5 would not be not compliant with the HDMI spec since shorting this line or connecting it to another source should do no damage.  In case of a short, the fuse should work but there isn't any current limiting if it were connected to another source.  I haven't had a chance yet to figure out whether it is the lack of 5V or the signal levels which are causing the problems with my monitors.  In the meantime, be aware there are potential issues of doing what I suggested - although from Luke's schematic, he does put VBUS on the HDMI 5V pin.

  • in reply to Jan Cumps

    I see.. Here the law is different for consumer items, and business-to-business items. Hobbyist products would fall under the general consumer legislation.. think it has to be fit for purpose in the UK. I suppose it's different if something is advertised as compatible with specific xyz, and guaranteed for that, it can't do nothing.

    Especially if it destroys/damages something with a standard HDMI connector on it, not sure the manufacturer could say it was experimental even if it was advertised like that, because hobbyists and DIY'ers are not expected to be qualified specialists to know any better. It's like me saying I 'know about cars' and help a friend out, I'd not be liable if it had faults that an expert would have noticed, because I'd not be expected to have the same knowledge as a car mechanic (provided I didn't try to mislead that I was a car mechanic).

  • The use case that I have found for a monitor or TV sourcing 5V on an HDMI connector is called MHL (Mobile High-Definition Link).  The 5V is used to power/charge the MHL source device (possibly a smartphone or tablet).  I think it was a bad idea to reuse the HDMI connector for this other standard.  I'll need to check if I have any MHL compatible ports or devices.  Maybe there is a case of a standard HDMI port having this capability?

     

    https://en.wikipedia.org/wiki/Mobile_High-Definition_Link

  • in reply to shabaz

    Over here, if you sell it as experimental, targeted for experimental users,  and declare it not fit for production use, you can.

  • in reply to shabaz

    They sure cranked out a lot of RP2040 products in a hurry.  Be interesting to see how well they work.  I've used their "Thing" boards in the past and been pretty satisfied.  Maybe you've had other experiences?

  • in reply to DAB

    I think it's just a statement of assuming some risk if you use a SparkX product.

     

    It's a learning experience, so I'm okay with it.  If this had been sold as a "standard" product, I would have complained image.