.. _bm_lpuarte_sample:

LPUARTE
#######

.. contents::
   :local:
   :depth: 2

The LPUARTE sample demonstrates how to configure and use the LPUARTE driver as a low power alternative to regular UART.

Requirements
************

The sample supports the following development kits:

.. tabs::

   .. group-tab:: Simple board variants

      The following board variants do **not** have DFU capabilities:

      .. include:: /includes/supported_boards_all_non-mcuboot_variants_s115.txt

      .. include:: /includes/supported_boards_all_non-mcuboot_variants_s145.txt

   .. group-tab:: MCUboot board variants

      The following board variants have DFU capabilities:

      .. include:: /includes/supported_boards_all_mcuboot_variants_s115.txt

      .. include:: /includes/supported_boards_all_mcuboot_variants_s145.txt

The sample also requires the following pins to be connected, as defined in the boards :file:`board-config.h` header:

  .. include:: /includes/lpuarte_board_connections.txt

  #. For two-device setup:

    - Device 1 **LPUARTE TX** → Device 2 **LPUARTE RX**
    - Device 1 **LPUARTE RX** → Device 2 **LPUARTE TX**
    - Device 1 **LPUARTE REQ** → Device 2 **LPUARTE RDY**
    - Device 1 **LPUARTE RDY** → Device 2 **LPUARTE REQ**
    - Connect **GND** between both devices.

  #. For single-device loopback setup:

    - **LPUARTE TX** → **LPUARTE RX**
    - **LPUARTE REQ** → **LPUARTE RDY**

Additionally, the sample requires a logic analyzer to observe the LPUARTE activity and a current measurement instrument to measure the current.

Overview
********

The sample initializes the application LPUARTE instance, specified in the :file:`board-config.h` file in the board.
It then implements a simple loopback using a single LPUARTE instance.
By default, the console and logging are disabled to demonstrate low power consumption when UART is active.

User interface
**************

LED 0:
  If configured, lit when the device is initialized. (Configurable using the :kconfig:option:`CONFIG_SAMPLE_LPUARTE_INIT_LED` kconfig option)

Building and running
********************

This sample can be found under :file:`samples/peripherals/lpuarte/` in the |BMshort| folder structure.

For details on how to create, configure, and program a sample, see :ref:`getting_started_with_the_samples`.

Testing
=======

You can test this sample by performing the following steps:

#. Compile and program the application.
#. Connect the logic analyzer to the LPUARTE pins, to confirm UARTE activity.
   The request/response pins are HIGH in the idle state.
   When a transmission starts, the pins are pulled LOW to signal the start of data transfer.
   At the same time, activity should be visible on the UART RX/TX pins.

   Configure the logic analyzer to use an ``asynchronous serial (UART) protocol`` on the RX/TX
   connection.
   With the default sample configuration, use a baud rate of ``115200``, and verify that a
   ``5-byte message`` is transmitted with the decimal values ``1``, ``2``, ``3``, ``4``, and ``5``.
#. Measure the current to confirm that the power consumption indicates that high-frequency clock is disabled during the idle stage.

During the idle stage, the UARTE receiver is ready to start reception, as the request pin wakes it up.