Yun REV2 - Handshake

Hardware Arduino Yún
1

recently got my new REV2 YUN,

I'm trying to get the HANDSHAKE between the OpenWRT and Atmel processors to work between gpio19 and pin7 as described in the below (this worked perfectly with YUN rev1)

https://forum.arduino.cc/index.php?topic=290149.msg2029465#msg2029465

This doesn't seem to work anymore...

  1. was looking for REV2 schematics to see if anything changed but can't find it anywhere, where can i find it?

  2. I noticed that the export that used to go to: "/sys/devices/virtual/gpio/gpio19/" now goes to: "/sys/devices/platform/ath79-gpio/gpiochip0/gpio/gpio19" , verified the direction and value and they were OK, same for gpio22, but it seems that nothing reaches PIN7 of the Atmel,
    any ideas?

Thanks,

2

I just spent some time looking for the Rev 2 schematic, and have come up empty. I came up with the process described in your link by studying the original schematics. It seems they might have changed some internal details about the way things are hooked up, and I think it will be quite difficult to figure it out without an updated schematic. In one third-party blog post about the new board, I was excited to see a link to the schematic - while it looked different (cleaner and fewer pages) than the old schematic I saved, it was dated 2014, so it is clearly for the original version.

If anyone can find the new schematic, please post a link here.

3

They added the schematics to the documentation under:

4

yaeerm:
They added the schematics to the documentation under:
Arduino Yún Rev 2 — Arduino Official Store

Thank you, that wasn't there a couple days ago. When I looked, the documentation tab only listed the on-board indicators section.

yaeerm:
This doesn't seem to work anymore...

Looking at the schematic, it appears that there is no longer any handshake line between the Linux and AVR sides of the Yun Rev 2. :cry:

The only signals that I see that are common between the two processors pass through the three level converters in the upper left corner of the schematic. These include the Rx/Tx lines for Bridge communications, as well as the SPI lines for remote AVR firmware upgrades (MISO/MOSI/SCK/SS.) There there is the one-way connection from the Linux to the AVR side to allow the Linux side to reset the AVR processor.

While there is no longer a line dedicated to this function, I suppose it should be possible to do something similar using the SPI lines, assuming there is a line there that is not used by your application. Even if the SPI lines MISO/MOSI/SCK are used, you may be able to use the SS line as a handshake, by using other digital pins as the slave select signal.

The bi-directional lines I see between the two processors are:

Signal AVR Linux Enable
----------------- --------- -------------- -----------
Bridge Comm D0 UART_TX GPIO23
Bridge Comm D1 UART_RX GPIO23
MISO D14 GPIO8 GPIO21
SCK D15 GPIO11 GPIO21
MOSI D16 GPIO27 GPIO21
SS D17 GPIO26 GPIO21

Note that these are split into two groups, each with their own enable: the comm lines, and the SPI lines. If you enable one of these signals in a group, you enable all of them. Also note that on the AVR side, the SPI lines are all on the 6-pin ICSP connector.

I find it curious that the schematic indicates that the shield and ICSP connectors are to be yellow - Is the Rev 2 based on Seeed's Seeduino Cloud clone (which uses the yellow connectors)? Comparing it to Seeed's schematics, for the most part, it looks like a copy/paste of the major functional blocks, simply re-arranging them on one large sheet and leaving off a few Seeed features like the Grove connectors...

5

Thanks for the insights,

Naive question: how would one use the SS signal?