Hello,
For my own needs, I continued to investigate thinking that it could still serve others.
Between revision 1 and revision 2, many components have been replaced by equivalents, so here we are only going to talk about functional differences that are of interest to the "maker".
The Arduino Yun 2 is shipped with the same MIPS-based, 400MHz Atheros AR9331 WiFi SoC, 64MB of DDR2 RAM, and 16MB of flash found on the Rev 1. The AR3991 chip’s built-in WiFi continues to be 2.4GHz 802.11b/g/n. Like its predecessor, the new model also offers a 16MHz Atmel ATmega32U4 chip running Arduino code, with 2.5KB RAM, 32KB flash, 20x DIO pins, 12x analog outputs, and 7x PWM interfaces.
The board is once again equipped with an Ethernet port, USB host port, and microSD slot. However, the 10/100 Ethernet port has been better integrated to the rev 2 board that avoids accidental short circuits when using certain Arduino shields.
The USB port has been flipped from vertical to horizontal to make for a more compact profile
these two improvements greatly facilitate the design and attachment of a personal shield.
But still that the space between the connectors is not at a space of 2.54! it remains a flaw to install a breadboard.
A micro-USB client port is used for a power input to the “much better, more robust power supply,” and and 4x LEDs are available. The board appears to have the same 73 x 53mm dimensions as the original.
And the location of the holes is as badly placed on one as on the other making difficult the fixing of a shield thanks to standard spacers !!
Regarding the electronic diagram, it has unfortunately not gained clarity or care and I think that a trainee should apply ...
Strangely, there are no more connectors, but to confuse the names of the headers have been changed
J11->J3
J12->J4
J10->J5
J9->J7
I already talked about the power supply VIN of the card and I will not go back on it, maybe precisely the fault to the trainee ... Moreover the HUB is not at 16MHz but 12MHz
Anyway the diagram shows a bi-directional protection by a resettable fuse if you use the micro USB port to feed your card the time of the focusing.
It would have been better to have a diode to protect your USB port I think.
The handshake was removed, making the feature at PE6/D7/INT6 available that was not completely free since this feature had not been documented.
In the same way the serial communication of the monitor by the micro USB and the GPIO 6 of the processor have been removed from the header.
Nothing to say about the Wifi module, which does not even appear on the diagram, just can we guess that it uses the pins P0_Tx+- / Rx+- Atheros. RJ45 “WAN” using P4_T +- / Rx+ -
Of course, the serial link wich is used by the bridge to communicated between the µP/µC through tty0/Serial1, and makes the strength of the YUN, has been maintained as well as the possibility of invalidating it by the GPIO 23 of the µP.
And the GPIO 18 always allows the µP to reset the µC.
Materially and functionally the two versions remain mostly compatible without much effort but it's a pity anyway.
Regarding the OS, revision 1 comes with “Linino” and revision 2 “LEDE” both come from OpenWrt but I admit that I do not understand the relationship between these two systems because the Linux side is very poorly documented.
See my post on the update.
https://forum.arduino.cc/index.php?topic=612524.0
Anyway, it does not seem silly to install on revision 2 an 1.5.3 software version with Linino available on the offical page:
Indeed, the updated version “LEDE” is not available on the Arduino site and seems more in the state of development than release (Available on GitHub).
Due to continuous improvements and suggestions coming from both the OpenWrt community and the Arduino community, version of OpenWrt-Yun installed on your Yún rev. 2 may be out of date. Please check the upgrade tutorial and be sure you're running the latest version available.
https://www.arduino.cc/en/Tutorial/YunSysupgrade
That website does not make the difference between a Yun Rev 1 with linino 1.5.2 and a Yun Rev 2 with LEDE 17.11 ...
Very weird!
For the moment, I have not managed with this version to completely inhibit the bridge that seems to interfere with my μC / μP C exchanges on the Serial1 ATMega / ttyATH0 Atheros port:
See :
https://forum.arduino.cc/index.php?topic=557667.0
As a general conclusion, the Linux side remains very poorly documented for both versions (Applications Startup, Bridge Usage, Python, C / C ++ and GPIO access / use) for the hobbyist and even the professional in electronic. Perhaps more clear for a linux developer.
I think the community may be losing interest because of that!
And I only have the excellent "Arduino meets linux” to recommend.
Good luck to you.