• https://embedded.fm/episodes/475?rq=zephyr – Nämner bland annat att det finns några tänkta sätt att strukturera sina projekt för att inte blanda in sin projekt-kod i zephyr-repot
• Youtube Linux Foundation – Zephyr Project: RTOS Start-up and Initialization Flow

• Introduction to Zephyr Part 1: Getting Started
• Introduction to Zephyr Part 2: CMake Tutorial
• Introduction to Zephyr Part 3: Kconfig Tutorial
• Introduction to Zephyr Part 4: Devicetree Tutorial
• Introduction to Zephyr Part 5: Devicetree Bindings

• Recommended KConfig page

• Zephyr API
• Zephyr services
• Zephyr KConfig
• Cmake

Bygg Zephyr-projekt med overlay

west build -p always -b esp32c6_devkitc -- -DDTC_OVERLAY_FILE=boards/esp32s3_devkitc.overlay

Öppna menuconfig

west build -p always -b esp32c6_devkitc -t menuconfig

Bygg med extra conf file

west build -p always -b esp32c6_devkitc -- -DEXTRA_CONF_FILE=boards/esp32s3_devkitc.conf 

Ladda kod

python -m esptool --port COM19 --chip auto --baud 921600 --before default_reset --after hard_reset write_flash -u --flash_size detect 0x0 .\build\zephyr\zephyr.bin

Öppna menuconfig

west build -p always -b esp32c6_devkitc -t menuconfig

Sparas till ./build/zephyr/.config som kommer tas bort vid nästa bygge.

För att göra persistent, kolla diff mellan ./build/zephyr/.config.old

# diff build/zephyr/.config.old build/zephyr/.config
574a575,576
> # CONFIG_STACK_CANARIES is not set
> CONFIG_STACK_POINTER_RANDOM=0
1136c1138
< # CONFIG_TEST_RANDOM_GENERATOR is not set
---
> CONFIG_TEST_RANDOM_GENERATOR=y
1137a1140,1141
> CONFIG_TIMER_RANDOM_GENERATOR=y
> CONFIG_TEST_CSPRNG_GENERATOR=y

Lägg sedan detta i antingen appens prj.conf eller ännu bättre i en board-specifik config

# File: boards/esp32s3_devkitc.conf
# CONFIG_STACK_CANARIES is not set
CONFIG_STACK_POINTER_RANDOM=0
CONFIG_TEST_RANDOM_GENERATOR=y
CONFIG_TIMER_RANDOM_GENERATOR=y
CONFIG_TEST_CSPRNG_GENERATOR=y
# CONFIG_SAY_HELLO=y

Och lägg med denna till bygget med -DEXTRA_CONF_FILE=boards/esp32s3_devkitc.conf

west build -p always -b esp32c6_devkitc -- -DEXTRA_CONF_FILE=boards/esp32s3_devkitc.conf 

• Devicetree 0.4 specification
• Zephyr DTS page
• Zephyr DTS bindings

• DTS – Device Tree Source
• DTC – Device Tree Compiler
• .dtsi – Device Tree Source Include file

Zephyr DTS Syntax Structure

In the boards folder for esp32s3_devkitc there is a DTS file for the appcpu, /opt/toolchains/zephyr/boards/espressif/esp32s3_devkitc/esp32s3_devkitc_appcpu.dts.

/*
 * Copyright (c) 2024 Espressif Systems (Shanghai) Co., Ltd.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
/dts-v1/;

#include <espressif/esp32s3/esp32s3_appcpu.dtsi>
#include <espressif/partitions_0x0_amp.dtsi>

/ {
	model = "Espressif ESP32S3-DevkitC APPCPU";
	compatible = "espressif,esp32s3";

	chosen {
		zephyr,sram = &sram0;
		zephyr,ipc_shm = &shm0;
		zephyr,ipc = &ipm0;
	};
};

&trng0 {
	status = "okay";
};

&ipm0 {
	status = "okay";
};

This #include <espressif/esp32s3/esp32s3_appcpu.dtsi> includes a devicetree source include-file which in turn includes #include "esp32s3_common.dtsi".

Int the file /opt/toolchains/zephyr/dts/xtensa/espressif/esp32s3/esp32s3_common.dtsi there is a part defining the alias gpio0 for the path /soc/gpio/gpio@60004000.

			gpio0: gpio@60004000 {
				compatible = "espressif,esp32-gpio";
				gpio-controller;
				#gpio-cells = <2>;
				reg = <0x60004000 0x800>;
				interrupts = <GPIO_INTR_SOURCE IRQ_DEFAULT_PRIORITY 0>;
				interrupt-parent = <&intc>;
				/* Maximum available pins (per port)
				 * Actual occupied pins are specified
				 * on part number dtsi level, using
				 * the `gpio-reserved-ranges` property.
				 */
				ngpios = <32>;  /* 0..31 */
			};

The compatible = "espressif,esp32-gpio"; tells Zephyr to look for a bindings file containing the similar line (file name doesn't really matter, but is by convention the same).

Binding file can be found in /opt/toolchains/zephyr/dts/bindings/gpio/espressif,esp32-gpio.yaml

# Copyright (c) 2019, Yannis Damigos
# SPDX-License-Identifier: Apache-2.0

description: ESP32 GPIO controller

compatible: "espressif,esp32-gpio"

include: [gpio-controller.yaml, base.yaml]

properties:
  reg:
    required: true

  "#gpio-cells":
    const: 2

gpio-cells:
  - pin
  - flags

Also at the location for the board files is the /opt/toolchains/zephyr/boards/espressif/esp32s3_devkitc/esp32s3_devkitc-pinctrl.dtsi device tree source include file. The start of the file looks like this:

/*
 * Copyright (c) 2024 Espressif Systems (Shanghai) Co., Ltd.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/dt-bindings/pinctrl/esp-pinctrl-common.h>
#include <dt-bindings/pinctrl/esp32s3-pinctrl.h>
#include <zephyr/dt-bindings/pinctrl/esp32s3-gpio-sigmap.h>

&pinctrl {
	uart0_default: uart0_default {
		group1 {
			pinmux = <UART0_TX_GPIO43>;
			output-high;
		};
		group2 {
			pinmux = <UART0_RX_GPIO44>;
			bias-pull-up;
		};
	};

	i2c0_default: i2c0_default {
		group1 {
			pinmux = <I2C0_SDA_GPIO1>,
				 <I2C0_SCL_GPIO2>;
			bias-pull-up;
			drive-open-drain;
			output-high;
		};
	};

The line #include <dt-bindings/pinctrl/esp32s3-pinctrl.h> refers to the file /opt/toolchains/zephyr/include/zephyr/dt-bindings/pinctrl/esp32s3-pinctrl.h which has a lot of defines used in the device tree include file.

#define UART0_TX_GPIO43 ESP32_PINMUX(43, ESP_NOSIG, ESP_U0TXD_OUT)

All of the files in /opt/toolchains/zephyr directories are default files and the device tree thingies can be overridden in you project with a overlay-file.

Kernel DTS Coding Style

• Names kan inte ha understreck, men kan ha bindestreck.
• Lables kan inte ha bindestreck men kan ha understreck.
• Names kan ha brädhögar och snabel-a i namnet, ingen magi.
• Property names kan inte ha understreck, men kan ha bindestreck
• I C-kod kommer bindestreck i aliases att automatiskt översättas till understreck

Dessa är två speciella noder i device-trädet som DTC behandlar speciellt. Dessa går att fylla på för att ställa in vissa saker eller introducera alias.

/ {
     chosen {
             zephyr,console = &uart0;
     };

     aliases {
             my-uart = &uart0;
     };

     soc {
             uart0: serial@12340000 {
                     ...
             };
     };
};