A discussion for using tty communication through the SPI bus (/dev/ttySPI0) between the two Yun processors, for use with Firmata or other software.
This thread is a fork of an original thread about tty through the serial bus (/dev/ttyATH0) and Firmata:
The web page below on the Linino website talks about a tty driver they developed that communicates through the SPI bus instead of the serial bus, and using the StreamSPI class with Firmata:
I could be wrong but I'm getting the impression this feature has not yet been officially released. If you follow the steps below and you run into problems then you may or may not be able to receive support. Hopefully the Arduino/Linino team will be able to shed more light on this feature's status at some point in time.
Within the linino_dev download branch, the kmod-spi-tty-ds kernel module did not start being natively compiled as part of the development images until Dec 4th 2013, as per its build-config.txt file at that time.
I saved the following development image to the root of my SD card, then followed the "Yun sysupgrade tutorial" on the main Arduino download page, erasing all my settings and data in the process:
Afterwards, a lsmod command confirmed the spi_tty_ds module was loaded. The /dev/ttySPI0 interface existed.