New PCB rev on the horizon

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Artcfox
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Re: New PCB rev on the horizon

Post by Artcfox » Wed Sep 16, 2015 8:29 pm

uze6666 wrote:
Perhaps the video expansion header could be moved closer to the back side to better allow such possibilities? ;)
Yeah some sort of port would be the best, but there's not much space as you know and I don't wan't to move stuff in that area otherwise I'll have to redo the routing.
My only other comment about the PCB concerns the audio out portion. I'm not familiar with the circuitry inside the television that accepts the audio signal, but would adding a simple RC low-pass filter before the audio out jack help suppress any harmonics, or is that already handled inside the television?
From my experience, the TV already does it. Initially there was a RC filter but it kinda muffle the sound and worst it created some slight artifacts in the video signal probably due to some ground plane thing that I could never resolve.
Cool.

One more thing I wanted to ask about is the non-level shifted connection between the ESP8266 and the ATmega644.

The datasheet for the ESP8266 lists a max working voltage of 3.6V, but then it also has this note:
All digital IO pins are protected from over-voltage with a snap-back circuit connected between the pad and ground. The snap back voltage is typically about 6V, and the holding voltage is 5.8V. This provides protection from over-voltages and ESD. The output devices are also protected from reversed voltages with diodes.
But on the Adafruit HUZZAH ESP8266 Breakout they added level shifting on the UART and reset pin. So, which is correct?

The datasheet for the ESP8266 also lists a maximum current of 12mA, does that mean that we should also limit the current on the UART and reset pins with series resistors?

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uze6666
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Re: New PCB rev on the horizon

Post by uze6666 » Wed Sep 16, 2015 10:54 pm

The ESP supports pretty well 5V for I\Os (as mentioned in the spec). I don't know why the huzzah has all those extra parts, perhaps to be extra safe? In any case, the design philosophy I took for the uzebox is the minimum parts that works correctly. The Uzenet module don't have those extra resistors and level shifter and it works just fine.

Artcfox
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Re: New PCB rev on the horizon

Post by Artcfox » Thu Sep 17, 2015 12:35 am

uze6666 wrote:The ESP supports pretty well 5V for I\Os (as mentioned in the spec). I don't know why the huzzah has all those extra parts, perhaps to be extra safe? In any case, the design philosophy I took for the uzebox is the minimum parts that works correctly. The Uzenet module don't have those extra resistors and level shifter and it works just fine.
Okay, I just wanted to make sure! (I remember it being a huge hassle for me trying to find something that ran at 3.3V that I could use to reflash the firmware on my ESP8266-01 with, and I ended up just hooking it directly into the GPIO pins of my Raspberry PI board. Maybe I'm just too cautious?)

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uze6666
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Re: New PCB rev on the horizon

Post by uze6666 » Thu Sep 24, 2015 12:41 am

New boards are in! Can't wait for the ESP-12E modules to arrive now. :D
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D3thAdd3r
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Re: New PCB rev on the horizon

Post by D3thAdd3r » Thu Sep 24, 2015 12:48 am

You are the man sir! It's a beauty :ugeek:

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uze6666
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Re: New PCB rev on the horizon

Post by uze6666 » Thu Sep 24, 2015 1:29 am

Let's hope my wiring is good, I didn't do a lot of post checks on the gerber files so fingers crossed.

Artcfox
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Re: New PCB rev on the horizon

Post by Artcfox » Thu Sep 24, 2015 3:59 am

Looks good! I'm very curious if you have better luck than I did with the 27 pF capacitor replacement for the notch filter. I had a really hard time trying to get the 18 pF one unsoldered because of how tight the space was between the other components, and I ended up just cutting it off and then soldering a 27 pF one on the bottom side of my board. :(

Without being able to switch back and forth between the two values, it's hard to say how much it helped.

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uze6666
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Re: New PCB rev on the horizon

Post by uze6666 » Thu Sep 24, 2015 5:03 am

Artcfox wrote:Looks good! I'm very curious if you have better luck than I did with the 27 pF capacitor replacement for the notch filter. I had a really hard time trying to get the 18 pF one unsoldered because of how tight the space was between the other components, and I ended up just cutting it off and then soldering a 27 pF one on the bottom side of my board. :(

Without being able to switch back and forth between the two values, it's hard to say how much it helped.
Not tested yet, was about to send the order as I was waiting to see what I would need for Uzenet...

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Re: New PCB rev on the horizon

Post by D3thAdd3r » Sun Oct 04, 2015 7:37 pm

I have a bit of curiosity regarding the video expansion header that stems from my failure to actually get RGB from the current standard PCB. I hooked up the appropriate pins to a SCART cable and fed that to a SCART->HDMI upscaler and I would get a split second of rolling picture then nothing. It seems the upscaler then tried S-Video/Composite trying to see what format it was. I tried everything I could think of but could not get anything to stay locked. I looked at some of the SCART enable lines and played with them, unfortunately I tried without proper resistance and smoked the upscaler(forget what the SCART pin is called that wants some low voltage for enable?) with 5v :roll:

My question, is it necessary to disable the AD725 for such a thing to work? I suspect yes, and does my memory serve me that there is a way to do that in software? I can't see how it could work the with AD725 on the RGB bus unless it can go tristate. Otherwise I guess you would need to cut the traces to the 725 to keep it from interfering. I had finally got around to making what I thought would be quick and easy work, but now I am truly puzzled. E/Uzebox did work with the upscaler but it seems I can't make an equivelant circuit without modification. If it doesn't work and it was some simple change perhaps it would be good for the new revision?

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uze6666
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Re: New PCB rev on the horizon

Post by uze6666 » Mon Oct 05, 2015 1:13 am

I never used A/V port, don't even know if the writing is ok (but it should). The signals you need are all inputs to the AD725 so can't see how disabling it would made any changes. But it's only a gut feeling. Looking at Harty's schematic, the only obvious difference is that there are no caps between the DAC and the SCART port. That suggests to me that perhaps it requires DC signals vs. the AD725 that needs to have it removed. Also there seems to be a 220Ohm resistor on the CSYNC pins.

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