First off, I'm not a Linux expert, so I can't really help you with uboot, but hopefully I can help get you to the prompt.
Resetting for BOTH the wi-fi and the linux part NOT responding 5s, 30s, 10 min !!!!!!!!
The long and short presses of the reset button are to get you out of trouble if you misconfigured the WiFi settings, or mangled up some configuration files to the point where you want to start over. If Linux is not booting normally, that reset button isn't going to help you.
The Catch-22 with the reset button is that it isn't active until Linux has fully booted up. Once booted, it starts looking at the reset button, times how long it's been held down, and then runs one of two different scripts depending on the time. But if Linux isn't fully booting, it's not running the button detection code, and that button doesn't help you.
That reset button is NOT like the factory reset button on a many devices where you press and hold it while powering on, or shortly after power on. It won't fix a board that does not boot properly.
So, is it possible to make linux do the UBoot so I can interrupt it and get the ar7240
It should be possible, unless Linux is totally dead and unresponsive. The key is that you need to get to the console prompt, and to do that you need to go through a sketch:
- Make sure no shield or external circuitry is connected to shield I/O pins 0 and 1
- Connect your Yun to your computer using a USB cable (you can't do this over the network, because the network is controlled by the Linux side.)
- Select your Yun's USB port in the Arduino IDE's Port menu
- Load the YunSerialTerminal example sketch onto your Yun
- Open the SerialMonitor
- Give a short press of the YUN RST button
- You should see the initial Linux boot sequence go by, including instructions on what to type to get the uboot prompt (which varies according to the Linux version you are running.)
You won't have much time to enter that response that breaks you out of the boot process and enters the uboot command line. You will likely have to do this once to see what you need to type, then type that in the send string box of the SerialMonitor. Then, hit YUN RST again, and quickly hit the SerialMonitor's Send button when the prompt appears. Once you are in the uboot prompt, the special timing concerns end.