Of course I meant to desolder R104 and use direct connection between GPIO pin and HDMI pin 13 (via R104 pad). But as I wrote manufacturer uses here additional MOSFET between HCEC from H3 and HDMI. If HCEC signal from H3 was different than HDMI voltage level I'd understand this solution. But here we have same voltage, so transistor is used probably to protect HDMI somehow. This way direct connection between GPIO and HDMI could be also dangerous. Especially that in OrangePiPC and One models Xunlong got rid of all protection Zenner diodes which are on the schematics. There are empty soldering pads only left. I compared it with photos of Pi 2 and Plus versions and there are all diodes in these models. So even using power supply higher than 5.3-5.5V can be dangerous for all connected devices (via USB and HDMI) because there are no protections left. Typicaly USB data lines also have Zenner diodes at 3.3V level and power line at 5V. There are no such diodes on our PCBs. Probably that's why the price is so low.
Regarding video stutter. I tested it in the morning. Test is very simple. You don't even need to play anything. Just start OpenELEC and observe nice smooth RSS stream scroller at the bottom of the screen. It freezes for a fraction of second every 10-15 seconds.
As I mentioned I used only 0224 version which suffers from stuttering. How to get previous versions? I can burn them and check if there is any proper version.
ok, what I found out currently:
git commit 92926ea2c6b44b6c7e19b34c3c726599648239ae
- RSS feeds works fine
- video works fine
git commit 5e13869815b09e6407e1404c9c853ffc9e255eee
- RSS feeds stutter
- video sttuter lightly
git commit f32cae9b53ed9e9386d5d5c168290b20aaa6e540
- RSS feeds stutter
- video sttuter heavily
Unfortunately, I won't have time this weekend to debug further. If anyone feels pinpointing which commit is at fault, please do so.
@cbm,
I consult my friend which is electronic expert and he thinks also that mosfet is some kind of protection. That means that trace should be cut in order to connect properly, which I don't like. I will still investigate proper CEC solution.
I also found such version: OpenELEC-H3.arm-7.0-devel-20160209211353-r22052-gf608afb.img.gz
And it also seems to play smooth, but there is no RSS scroll.
Regarding CEC - I don't like the idea of cutting trace before MOSFET. There is simply no room here on PCB, everything is very tiny. On OPiPC even worse.
I'd try OPiOne because as I mentioned also Zidoo implements CEC via PA21, so I'd have 2 systems with CEC.
It's a shame that Xunlong advertises OrangePi as CEC compatible when it is not natively supported via HCEC signal from H3.
CEC is 3 volts and also 27k pull-up is needed. At least Opi PI PC has all the electronics (resistors, transistor, diodes) needed to drive CEC pin of hdmi, but we would need to cut and attach the gpio to the trace that goes to the soc...
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