01-09-2019, 05:36 PM
t4_4t, first of all I want to thank you very much for the patience in answering my questions and the help provided, giving also the fact writing in English is not an easy task for you (BTW, English is not my native language also)
Now...
You have understood very well. My biggest problem, apart from finding too late that all my best guesses were wrong (shame on me for having trusted too much the "official" documentation), is that I had planned to fit the second Ethernet port in this case, where there is just space for one of the (now defunct) WDLABS hard disk, and the MagJack in one of the corner, for which I had do to do a cut in one of the corners so that the MagJack can slide in, and to push the hard disk up by slightly less than 1 cm, so that the SATA connector doesn't clash with the MagJack.
If you look at the pictures I have attached, there's really no space left where I can fit the (unexpected) voltage regulator and, worst, its two electrolytic capacitors which tend to be bulky compared with the compactness of the other components, hence my reasoning in trying to use the 3.3V already available on the P5+ connector. I could push up further the HD, where not for the caps it could have been a viable solution, but really there isn't space. I'll take your recommendations and experiment results (thank you for sharing them) to look for a different solution as my board is 4GB RAM model. Perhaps a voltage divider would suffice, assuming the provided 3.3V is stable? Just guessing, I stopped working with this stuff a very, very long time ago and I've forgotten a lot.
Ohm's law tells us that with 62Ω and 1.8V you are applying on the pulled-up pin a 30 mA current, whatever it means. PHY TX/RX pins are working in the analogical domain, also, not digital.
What are the above? The resistor values for a voltage divider?
Thanks!
Now...
(01-09-2019, 01:00 AM)t4_4t Wrote: > 3.3v can be used instead of 1.8v ? If so, 1.8v-regulator do not need.
I understood that the point of your remark is like the above.
(My English understanding is as you are aware)
You have understood very well. My biggest problem, apart from finding too late that all my best guesses were wrong (shame on me for having trusted too much the "official" documentation), is that I had planned to fit the second Ethernet port in this case, where there is just space for one of the (now defunct) WDLABS hard disk, and the MagJack in one of the corner, for which I had do to do a cut in one of the corners so that the MagJack can slide in, and to push the hard disk up by slightly less than 1 cm, so that the SATA connector doesn't clash with the MagJack.
If you look at the pictures I have attached, there's really no space left where I can fit the (unexpected) voltage regulator and, worst, its two electrolytic capacitors which tend to be bulky compared with the compactness of the other components, hence my reasoning in trying to use the 3.3V already available on the P5+ connector. I could push up further the HD, where not for the caps it could have been a viable solution, but really there isn't space. I'll take your recommendations and experiment results (thank you for sharing them) to look for a different solution as my board is 4GB RAM model. Perhaps a voltage divider would suffice, assuming the provided 3.3V is stable? Just guessing, I stopped working with this stuff a very, very long time ago and I've forgotten a lot.
(01-09-2019, 01:00 AM)t4_4t Wrote: Regarding the 1.8v-regulator, I described it based on this fact.
Again again, I think that their design (terminated to 1.8v) is reasonable.
*) However, "62Ω" is a mystery. I am the first time to see such a number.
Ohm's law tells us that with 62Ω and 1.8V you are applying on the pulled-up pin a 30 mA current, whatever it means. PHY TX/RX pins are working in the analogical domain, also, not digital.
(01-09-2019, 01:00 AM)t4_4t Wrote: It was quite a while ago, I tried changing the voltage at the termination.
and it's experiment data still remained.
According to it, it is sensitive.
x 1.61v ((27|27 ) / 22) : 13/22
o 1.73v ((22|27 ) / 22) : 12/22
o 1.83v ((22|22 ) / 22) : 11/22
o 2.01v ((22|22|47) / 22) : 9/22
x 2.16v ((22|22|22) / 22) : 7/22
What are the above? The resistor values for a voltage divider?
Thanks!
