picotiny example doesn't show up via HDMI capture

[jeremyherbert]

Hi,

I have successfully flashed the picotiny example to the Tang Nano 9K and it works on my LCD monitor via HDMI. However, when I connect it to a HDMI capture device, the HDMI video is not detected. I have tried the Elgato Cam Link 4K as well as a generic USB HDMI capture device that you can buy on ebay/aliexpress: https://www.adafruit.com/product/4669 - in both cases I just get a black screen, and the status LED on the Cam Link indicates that there is no HDMI detected.

I have previously used these capture devices with the ULX3S ECP5-based dev kit, so I know they work with some form of HDMI from FPGAs.

Has this example been tested on a HDMI capture device? I also tried the Martoni HdmiCore code, but it gives the same result: Martoni/HdmiCore#7

[scpcom]

I can confirm this limitation:

• With TangNano 4k (TLVDS) HDMI works on my LG 32LH7000 TV, 7inch 1024x600 HDMI LCD and on my HP x22LED monitor
• With TangNano 9k (ELVDS) HDMI works on 7inch 1024x600 HDMI LCD and on my HP x22LED monitor but NOT on my LG 32LH7000 TV
  Tested with HdmiCore on both and picotiny on TangNano 9k.
  Looks like a hardware limitation.

[nekomona]

Have just tested Tang Nano 9K on a cheapo, possibly MS2109-based USB 2.0 UVC capturer with several random HDMI cables around me and the picotiny example worked fine with all of them (apart from the horrendous image quality after MJPEG compression).

It could be some dev board - cable - adapter combinations that fails the signal requirement at the physical level. Sadly I have little idea of what can be done with it. ╥﹏╥

[hvegh]

When i plug the Tang Nano 9K in port 1 (HDMI) no screen, but if i use port 2 on the TV (HDMI/DVI) output is shown..
Seems like picotiny does not implement HDMI fully yet, more like DVI for now..

[jaseg]

I got it to work without issues on both an older Dell monitor and on one of these fake USB 3.0 HDMI/USB UVC converters. Mine self-identifies as some unspecified "macrosilicon" product. One thing that tripped me up for a bit is that the HDMI socket on the board is rather tight, and plugging in a HDMI cable for the first time takes some force.

[hvegh]

The issue is resolved, the TangNano has AC coupled HDMI, while most computer based monitors seem to accept this. TV sets use open-drain HDMI inputs, which need conversion electronics to operate. See https://www.eevblog.com/forum/fpga/fpga-to-hdmi-variants/

[andryblack]

On my board not soldered R1 jumper (see schematic) after connect pads my tv detect signal and show picture.