# Base service

    camel: base
    status: stable

Base class for all services.

## Commands

    report command_not_implemented @ command_not_implemented {
        service_command: u16
        packet_crc: u16
    }

This report may be emitted by a server in response to a command (action or register operation)
that it does not understand.
The `service_command` and `packet_crc` fields are copied from the command packet that was unhandled.
Note that it's possible to get an ACK, followed by such an error report.


## Registers

    const instance_name?: string @ instance_name

A friendly name that describes the role of this service instance in the device.
It often corresponds to what's printed on the device:
for example, `A` for button A, or `S0` for servo channel 0.
Words like `left` should be avoided because of localization issues (unless they are printed on the device).

    ro status_code? @ status_code {
        code: u16
        vendor_code: u16
    }

Reports the current state or error status of the device. ``code`` is a standardized value from 
the Jacdac status/error codes. ``vendor_code`` is any vendor specific error code describing the device
state. This report is typically not queried, when a device has an error, it will typically
add this report in frame along with the announce packet. If a service implements this register,
it should also support the ``status_code_changed`` event defined below.

    rw client_variant?: string @ client_variant

An optional register in the format of a URL query string where the client can provide hints how
the device twin should be rendered. If the register is not implemented, the client library can simulate the register client side.

## Events

    event status_code_changed? @ status_code_changed {
        code: u16
        vendor_code: u16
    }

Notifies that the status code of the service changed.