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UART (HDLC)

UART (HDLC)

Sept 29, 2016

This section refers to the following sample application(s):

  • 02-uart



The UART serial port can be used by a computer or external microcontroller to communicate with your application. The 

 chip provides hardware-accelerated HDLC support for the UART port.

Your application can set up the UART device to trigger a notification whenever a valid HDLC frame is received over the serial port. The frame contained in this notification has already passed CRC verification, and the HDLC flags and escape characters have been removed. Similarly, your application can send a data frame over UART; the device will take care of the HDLC framing, character escaping and CRC calculation.

The 02-uart Sample Application

The 02-uart sample application creates two tasks, and defines 3 CLI commands. A companion Python script uart_app.py runs on your computer and connects to the UART API port of your device.

Setup

The diagram below illustrates the setup for running this sample application:

  • Your computer and 

     are connected over a USB cable.

  • Your 

     is programmed with the 02_uart sample application.

  • Your computer runs the following:

    • The uart_app.py Python script (available in the 

      /app/02-uart/ directory).

    • A terminal client to enter CLI commands for the 

      .



You need to know the API and CLI serial ports corresponding to your

. You will connect the uart_app.py Python script to the API port, and the terminal client to the CLI port.

Refer to the SmartMesh IP Tools Guide for information about how to identify the different serial ports.

Overview

The 02-uart sample application creates 2 tasks.

  • the uartTxTask task transmits a number of UART frames from your 

     to the uart_app.py Python script. The number of frames to send, their length, and the inter-frame delay are set using CLI commands.

  • the uartRxTask task listens for incoming UART frames, sent in this case by the the uart_app.py Python script.

The 02-uart sample application defines 3 CLI commands:

  • use len to specify the length, in bytes, of the frames the uartTxTask task transmits.

  • use delay to specify the duration, in ms, for the uartTxTask task to wait between two successive frames.

  • use tx to specify the number of frames to transmit, and trigger the uartTxTask task to start transmitting.

The uart_app.py Python script connects to the API port of your 

. It defines a number of commands allowing you to transmit UART frames to the 

. It also prints the UART frames it receives. Start the uart_app.py Python script by double-clicking on its file.



Before you run this application, make sure you have Python and pyserial installed on your computer.

Refer to the SmartMesh IP Tools Guide for installation instructions.

The uart_app.py Python script defines the same CLI commands are the 02-uart sample application, i.e. len, delay and tx. On top of those, the uart_app.py Python script defines the connect command to connect it to the API serial port of your 

.

You can type help on both the 02-uart sample application and the uart_app.py Python script to obtain the list of available commands.

Type help on the your 

:



> uart app, ver 1.0.0.2 SmartMeshIP stack, ver 1.2.1.5 > help help <command> Commands: mtrace mset mget minfo mlog mfs mseti mgeti mshow mxtal mhwlog len delay tx >

Type help in the uart_app.py Python script:

uart_app OCFDK Sample application > help Commands: connect <comPort> len <numBytes> delay <numMs> tx <numPackets> exit >

Send UART frames from the 

First, connect the uart_app.py Python script to the API port of your 

 (here on COM28).

> connect COM28 >

On the 

, type the following command to send 5 HDLC frames, of 10 bytes each, with an inter-frame delay of 100ms to the uart_app.py Python script:

> len 10 > delay 100 > tx 5 > Sending 5 UART packets, 10 bytes, delay 100 ms done.

The following is printed by the uart_app.py Python script:

uart RX (10 bytes) 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a uart RX (10 bytes) 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a uart RX (10 bytes) 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a uart RX (10 bytes) 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a uart RX (10 bytes) 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a

Receive UART frames at the 

On the uart_app.py Python script, type the following command to send 5 HDLC frames, of 10 bytes each, with an inter-frame delay of 100ms to the 

:

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