The Linux SPI slave device driver is to enable user access to SPI slave stepper motor FPGA design in my other post http://souktha.github.io/hardware/zybo-spi-stepper . This is the software part of that implementation on the Zybo Zynq7000. I reuse the original SPI slave I wrote earlier and expand its functionality a little bit more so that I can send the step count to the stepper motor.
It is desirable to have some visual feedback to user during system boot up process especially if the system takes more than few seconds to boot. For the Linux based set-top box that boot to the main GUI menu may take considerable amount of time depending on the number of processes it needs to start. Some system may need to program the FPGA bitmask, bring up the networking processes or bring up some externally connected devices. These steps add up to the total system boot up time. For system with video support, it is a good practice to have video up as soon as possible so that the user would know that the system is working and it is in the process of booting up the system. This is commonly known as putting the boot splash screen during boot process.
TI DM814x/AM287x evaluation platform (TI8148 EVM) can boot from various connected devices depending on the setting of the BTMode[4-0] pins as described in chapter 4.5.2.1 of its respective technical reference manual [1]. Typically the EVM boot its first stage of u-boot as the minimum boot loaders. TI calls it min-nand boot loader configuration. This minimum boot then bootstraps a secondary boot phase which is a a full featured u-boot for this platform. The EV platform has SATA H/W support where I will bring up the SATA HDD in the second phase of booting so that I can load the Linux kernel image from HDD instead of loading it from NAND device.
Digilent Zybo board is built around Xilinx Zynq-7000 family [1]. This Zynq-7000 is integrated with a dual-core ARM Cortex-A9 processor that has Linux support for it. In addition to this PS unit, the Xilinx 7-series FPGA is also integrated as the PL component of this SoC [2]. This demonstation will show how easy it is to decouple PS and PL components.
What I like about working with TI based platform is their easily accessible documentations. It is by far the most developers friendly unlike other chip vendors. This accessibility has enable me to experiment with the on-chip I/O subsystem components.
When I ssh from remote host machine to my local machine, say from outside place to host machine at home, I would like to directly access a device that is connected by serial console to my local machine, for example, a beaglebone black board that is connected to my home PC serial console ttyUSB0. I implemented a simple console server for this purpose.