_           .    .     _
| \         | \  | \   / |
| | __  ___ | |_ | | __| |
| |/ / / __|| __|| |/ /| |
|   < | /   | |_ |   < | |
|_|\_\|_|    \__ |_|\_\|_|

krtkl.com

snickerdoodle Ubuntu 20.04 SD Card README

================================================================================

The BOOT partition of this SD card (where this file is located) must contain the bootable components for the snickerdoodle and/or baseboard that the card will be used on. The BOOT partition contains a set of folders; each with the necessary boot components for a single system. To configure the SD card for the corresponding system, copy the contents of the folder into the top level of the BOOT partition.

Boot Components

By default, this SD card image contains the Linux kernel, U-Boot script and a couple of configuration files at the top level directory. These are files that are normally used by all configurations, although some customization may be desired to fit a specific application.

This un-configured SD card image does have the necessary bootloader or devicetree at the top level directory to boot the system. Before attempting to boot with this SD card, a boot.bin (bootloader) and devicetree.dtb (devicetree) must be added. To use a pre-built configuration, simply copy the contents of the directory to the top level of the BOOT partition. Below is an overview of the top-level files that should be found in the BOOT partition before booting:

boot.bin* devicetree.dtb* system.bit** uImage uEnv.txt config.txt uboot.scr

• Needs to be copied before booting ** Optional, needs to be copied before booting

Prebuilt Configurations

The BOOT partition of this SD card contains basic configurations for each snickerdoodle variant and various baseboards. Each configuration is represented by a directory containing the boot files. To boot a prebuilt configuration, copy the contents of the directory to the top level of the BOOT partition and insert the SD card into J6 on the snickerdoodle.

snickerdoodle Configuration

The config.txt file is used by the Linux init scripts to configure users and network settings. This file can be used to pre-configure the wireless access point and/or station network settings before booting. It can also be used to pre-configure user passwords in anticipation of remote login. See the config.txt file for details on setting network and system configuration parameters.

Additional Configuration

The uEnv.txt file contains additional configuration options such as setting the ethernet MAC (hardware) address and specifying the boot arguments. This file is read by U-Boot and can be used to specify a bitstream (system.bit by default) to be loaded by U-Boot.

Runtime and Pre-Boot Configuration

Various peripheral and boot settings are configured during runtime, or during the boot process, by snickerdoodle's platform microcontroller. Examples include: customizing LED behavior, antenna selection, and setting the boot mode. The necessary 'spi-ctrl' application and an accompanying README can be found in the /usr/local/bin directory. Visit krtkl.com/downloads for updates.

Devicetree and Linux Kernel Sources

For reference, devicetree (e.g. .dts, .dtsi) and Linux kernel sources have been included in the /usr/local/src directory.