"ROCK 64 STEREO AUDIO DAC ADD-ON BOARD", Is it okay if I turn on the power ?

[t4_4t]

I recently purchased "ROCK64 STEREO AUDIO DAC ADD-ON BOARD" from "PINE64-STORE".

The delivered items were different from the photos posted on the store.
So I checked the items before turning on the power.
(It can be judged at a glance that the circuit diagram that is published, and the item that arrived are different.
 Therefore, i can not discuss it on a circuit diagram basis)

As a result of the preliminary check, the following doubts came out.

When I measured the terminating resistors (R14/R15/R16/R17) used to drive the "pulse-trans",
its resistance value was 1Ω or less (actual measurement was about 0.3Ω).
In addition, "062" is printed on the chip resistor.
(It may be upside down "290", but I can not judge it, so I measured the value directly)

---

As another example of implementation,
We often see the use of values of several tens of ohms, for example about 50Ω.
But, I think this value of 1Ω or less is extremely small.

● Is this the correct value intended at design time ?

And

● When using it in this state does not damage rock64 itself ?

[tllim]

I recently purchased "ROCK64 STEREO AUDIO DAC ADD-ON BOARD" from "PINE64-STORE".

The delivered items were different from the photos posted on the store.
So I checked the items before turning on the power.
(It can be judged at a glance that the circuit diagram that is published, and the item that arrived are different.
 Therefore, i can not discuss it on a circuit diagram basis)

As a result of the preliminary check, the following doubts came out.

When I measured the terminating resistors (R14/R15/R16/R17) used to drive the "pulse-trans",
its resistance value was 1Ω or less (actual measurement was about 0.3Ω).
In addition, "062" is printed on the chip resistor.
(It may be upside down "290", but I can not judge it, so I measured the value directly)

---

As another example of implementation,
We often see the use of values of several tens of ohms, for example about 50Ω.
But, I think this value of 1Ω or less is extremely small.

● Is this the correct value intended at design time ?

And

● When using it in this state does not damage rock64 itself ?

Please post a photo so that able to determine whether PINE64 store deliver wrong board to you.

[t4_4t]

In the delivered item,
The termination point of the signals "TD+-/RD+-" and center-tap of "pulse trans" are connected to the same node.

*) same node: 1.8v Reference-Voltage
  This node is generated by a newly added parts (regulator) to the published "circuit diagram".

In this state, the value of the resistor that mounted on the board can not be measured accurately.
Because L of "pulse trans" interferes with the measurement of resistance.

Therefore, I removed the resistance from the board, and measured only the removed resistance.
Then the value of resistance was "62Ω", this is the similar value that was generally used.
And this value accords with the numerical value ("062") written on resistance.

Because I was able to confirm the above, my uneasiness point was canceled.
Therefore I turned on a power supply and really operated it.

It worked without a problem.

---

> Please post a photo so that able to determine whether PINE64 store deliver wrong board to you.

PINE64 store's photo:
https://www.pine64.org/?product=rock64-s...d-on-board

Published schematic:
http://files.pine64.org/doc/rock64/ROCK6..._Board.pdf

Delivered Item's photo:
https://forum.pine64.org/showthread.php?...5#pid42185

---

The reason why I bought this board is as follows.

As can be understood by referring to the following thread,
Nobody made it according to the published circuit diagram and succeeded in its operation.

"WARNING: internal 10 | 100 PHY requires magjack hardware!"
https://forum.pine64.org/showthread.php?tid=4724

My doubts are as follows
1). Why does it work with this "circuit diagram" ?
or
2). Why selling products that do not work ?
Because I thought that the fact must be either of the above.
My purpose of purchase was to confirm the above.

So, I had the opportunity to purchase "RockPro64", so i bought this product together.
After receiving the product, and seeing it, my doubts was solved immediately.

The received item is clearly different from the picture of the product being published and its circuit diagram.
And a lot of parts were added to the "EtherNet" related part of the received item.


… My estimation was a mistake. …
  The result was neither of the above doubt "1)" / "2)".

To unexpected things,
  The product that is currently on sale is different from "published photo / circuit diagram".
The fact was due to the above reasons.

Therefore,
  It is obvious that it will not work, even if it is created according to the published circuit diagram.


*) Finally.
  I present the "circuit diagram" of item that I actually make and worked well, and the parts used for it as examples.

RJ45-JACK(with pulse trans)
https://www.dacomwest.de/images/Dateien/...100715.pdf

Regulator-1.8v
http://www.unisonic.com.tw/datasheet/UT7500.pdf

*Note)
Parts used for "ROCK 64 STEREO AUDIO DAC add-on board" are …
  The terminating resistor is "62 Ω".
  The manufacturer of the regulator(1.8v) is unknown.
  There is no LED display function of "EtherNet".

[WrongWorld]

Regulator-1.8v
http://www.unisonic.com.tw/datasheet/UT7500.pdf

*Note)
Parts used for "ROCK 64 STEREO AUDIO DAC add-on board" are …
  The terminating resistor is "62 Ω".
  The manufacturer of the regulator(1.8v) is unknown.
  There is no LED display function of "EtherNet".

Isn't that they have used the 1.8V regulator output as they needed it for other means on the shield? Because I think otherwise they could have used the 3.3V VCC available on pin 1 of P5+, which is already regulated, so that you could omit from your scheme the regulator and its two electrolytic caps. Indeed, without knowing exactly the impedance of the RX/TX pins (I couldn't find the value in the RK docs, but I didn't look for it seriously TBH), one could use an equation and calculate the needed resistor value to obtain the same voltage drop on the pins, but having 3.3V as VCC.

SparkFun has a nice article on pull-up/down resistors

The other thing I've noticed in your schema is that the central transformer pin is hooked to VCC and to the capacitor. Indeed, I have left that end dangling on my schema, although I was suspicious about it.

I think it may be useful to add this RockChip wiki page the the Pine64's Rock64 Wiki site. There I've found the schema of a reference design, for instance. Also, on the Rock64 P5+ bus schema pin 21 is reported wrongly as GPIO2_D1 (Ethernet Speed) (and I did the same error in my schema), which is not correct as GPIO2_D1 is PHY's Ethernet Data LED. PHY's Ethernet Speed is GPIO0_D6, which I think is not available as it is used for SDMMC0_PWREN (i.e. the MMC) and not present on the P2 /P5+ connectors.

I wish Rock64 would have a proper/better documentation. IMHO is its weakest point and probably the main reason it is not as widespread as it could.

[t4_4t]

Because it was the purpose to convey the mistake of the published "circuit diagram and photo"
I have already accomplished the object here.

So, you can use the original thread in the future.