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https://github.com/bpbradley/zcalendar

Calendar API for Zephyr RTOS
https://github.com/bpbradley/zcalendar

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Calendar API for Zephyr RTOS

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# zcalendar



Calendar API for Zephyr RTOS.



## Features



* Ability to set and receive calendar time through a generic API where the backend is hidden from the user level. If a battery backed RTC is used, the calendar time will be retained through power cycles.



* Supports access from user threads via system calls so it operates the same with or without `CONFIG_USERSPACE=y`



## Supported Backends



* STM32 RTC

* Maxim DS3231

* Micro Crystal RV8263, RV3032



## Configuration



zcalendar is fully compatible with the west build system, and is designed to be easily integrated into any Zephyr project through the project's west manifest. It is configured through the project conf file, and depending on the backend, it may also need to be configured with the device tree.



### Kconfig



Enable with



```conf

CONFIG_CALENDAR=y

```



Enable the desired backend such as



```conf

CONFIG_STM32_RTC_CALENDAR=y

```



Refer to the Kconfig files to learn about optional configurations which can be used as well.



### Device Tree



Some backends need specific device tree configurations. This is something I would like to address in the future to make configuration clearer, but for now examples for configuration of each backend are included.



#### Maxim DS3231



The Maxim DS3231 backend leverages the existing driver implementation in the counter API. In this case,

you must select the appropriate device in the device tree for zcal to use internally. This can be done

using the included device tree bindings



```dts

&i2c0 {

  calendar_rtc: ds3231@68 {

    compatible = "maxim,ds3231";

    reg = <0x68>;

    label = "DS3231";

    isw-gpios = <&gpio0 0 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;

  };

};



/ {

  calendar{

    compatible = "calendar";

    label = "CALENDAR";

    rtc = <&calendar_rtc>;

  };

};

```



Or by using a chosen node



```dts

/ {

  chosen{

    zcal,rtc = &calendar_rtc;

  }

}

```



#### Micro Crystal RV



The Micro Crystal RV is independent of all zephyr drivers and APIs, and so includes its own device tree binding.



```dts

&i2c0 {

  calendar_rtc: rv@51 {

    compatible = "microcrystal,rv-calendar";

    reg = <0x51>;

    label = "RV8263";

  };

};

```



#### STM32



The STM32 implementation is independent of the counter API and does not rely on other devices like i2c, so it does not need any device tree configuration.



### Using West



Here is an example west manifest file. Modify according to your project needs



```yaml

manifest:

  remotes:

    - name: zephyrproject-rtos

      url-base: https://github.com/zephyrproject-rtos

    - name: zcal

      url-base: https://github.com/bpbradley

  projects:

    - name: zephyr

      remote: zephyrproject-rtos

      revision: main

      import:

        path-prefix: rtos

    - name: zcalendar

      remote: zcal

      revision: zephyr-v2.7.3

      path: modules/zcalendar

  self:

    path: app

```



## Sample Usage



Here is everthing needed for basic usage of the calendar API

with the Micro Crystal RV8263 backend



### Sample Configuration



```conf

CONFIG_CALENDAR=y

CONFIG_RV8263_RTC_CALENDAR=y

```



```dts

&i2c0 {

  calendar_rtc: rv@51 {

    compatible = "microcrystal,rv-calendar";

    reg = <0x51>;

    label = "RV8263";

  };

};

```



### Sample Code



```c

#include 

#include 



int main(){



    /* Get the device handle */

    const struct device * calendar = \

        device_get_binding(DT_LABEL(DT_NODELABEL(calendar_rtc)));



    if (calendar){

            /* Set the calendar time by epoch */

            struct tm * time;

            const time_t epoch = 1669843527;

            time = gmtime(&epoch);

            calendar_settime(calendar, time);



            /* Wait */

            k_sleep(K_SECONDS(5));



            /* Check the calendar time */

            int rc = calendar_gettime(calendar, time);



            /* Convert the time to a human readable string */

            if (!rc){

                char timestr[120] = {0};

                strftime(timestr,120,

                        "%A %B %d %Y %H:%M:%S", time);

                

                printk("%s", timestr);

            }

    }

    return 0;

}



```



### Note about User Mode



If the application is configured in User Mode, where

the api must interact with the kernel only via system calls,

there will be additional configuration required since from from

zephyrs perspective, the application is trying to make system calls.



In this case, the following configuration is needed



```conf

CONFIG_APPLICATION_DEFINED_SYSCALL=y

```



and the `SYSCALL_INCLUDE_DIRS` environment variable needs to include

the path to zcalendar. This can be done in `CMakeLists.txt` like so, *before the boilerplate is loaded*



```txt

list (APPEND SYSCALL_INCLUDE_DIRS 

    path/to/zcalendar

)

```