UPM

The UPM API is a high level sensor library for IoT devices using MRAA. See examples here. Back to index page.
SparkFun sensor images provided under CC BY-NC-SA-3.0.

UARTAT Class

Module: uartat
  • ID: uartat
  • Name: Generic AT Command Based UART Device
  • Category: other
  • Connection: uart

This is a generic UART device driver for accessing UART based devices that utilize an "AT" command set. Typically these devices are Radios, Modems, and similar devices that are configured and controlled by emitting "AT" commands.

Methods

UARTAT

(
  • uart
  • baudrate
)
Number

UARTAT object constructor for a UART specified by MRAA number.

Parameters:

  • uart Number

    Specify which uart to use.

  • baudrate Number

    Specify the baudrate to use.

Returns:

Number:

UARTAT

(
  • uart_path
  • baudrate
)
Number

UARTAT object constructor for a UART specified by PATH (ex: /dev/ttyUSB0)

Parameters:

  • uart_path String

    Specify path of UART device.

  • baudrate Number

    Specify the baudrate to use.

Returns:

Number:

readStr

(
  • size
)
String

Read character data from the device.

Parameters:

  • size Number

    The maximum number of characters to read.

Returns:

String:

string containing the data read.

writeStr

(
  • buffer
)
Number

Write character data to the device.

Parameters:

  • buffer String

    The string containing the data to write.

Returns:

Number:

The number of bytes written.

setBaudrate

(
  • baudrate
)

Set the baudrate of the device.

Parameters:

  • baudrate Number

    The baud rate to set for the device.

setResponseWaitTime

(
  • wait_time
)

Set the default time, in milliseconds, to wait for data to arrive after sending a command.

Parameters:

  • wait_time Number

    The response delay to set, in milliseconds.

dataAvailable

(
  • millis
)
Boolean

Determine whether there is data available to be read. In the case of a UART, this function will wait up to "millis" milliseconds for data to become available. In the case of an I2C device, the millis argument is ignored and the function will return immediately, indicating whether data is available.

Parameters:

  • millis Number

    The number of milliseconds to wait for data to become available.

Returns:

Boolean:

true if data is available to be read, false otherwise.

commandMode

(
  • cmd_chars
  • guard_ms
)
Boolean

Place the device in AT command mode. Many devices operate in a transparent mode and an AT command mode. Command mode is required to issue AT based commands. When in transparent mode, the device will usually listen for a special sequence of characters and delays, indicating that AT command mode should be entered.
On most devices, the sequence is: <wait 1 second>+++<wait 1 second>
For most devices, the wait time is 1 second (1000 ms) and the character sequence is "+++". These options can often be configured on the device.
This function will wait millis milliseconds, write the command characters (typically "+++"), then wait millis milliseconds again. At this time a read will be attempted, looking for the "OK" response indicating command mode was successfully entered.

Parameters:

  • cmd_chars String

    The character sequence to write, typically "+++".

  • guard_ms Number

    The number of milliseconds to delay before and after the cmd_chars are written.

Returns:

Boolean:

true if AT command mode ("OK" detected) was successfully entered, false otherwise.

inCommandMode

() Boolean

Check to see if the device is in command mode. This is accomplished by sending an "AT\r" command and seeing if "OK" or "0" is returned.

Returns:

Boolean:

true if AT command mode was detected, false otherwise.

drain

()

Read and throw away any data currently available to be read. This is useful to avoid reading data that might have been the result of a previous command interfering with data you currently want to read. This function is automatically called by commandWithResponse() , command() , and commandWaitfor() prior to writing the requested command to the device.

commandWithResponse

(
  • cmd
  • resp_len
)
String

Send an AT command and optionally return a response.

Parameters:

  • cmd String

    A character string containing the AT command to send, including the "AT" prefix and a terminating carriage return ("\r").

  • resp_len Number

    The maximum number of characters to read from the device.

Returns:

String:

The device response string, if any.

commandWaitFor

(
  • cmd
  • resp_len
  • waitString
  • millis
)
String

Send an AT command and return a response, while waiting for a specific string. If the string isn't found the returned string will be empty. If the string is found, the function will return immediately.

Parameters:

  • cmd String

    A character string containing the AT command to send, including the "AT" prefix and a terminating carriage return ("\r").

  • resp_len Number

    The maximum number of characters to read from the device.

  • waitString String

    The string to look for. If found, the response will be returned immediately regardless of the timeout setting.

  • millis Number

    The maximum number of milliseconds to wait for the string.

Returns:

String:

A string containing the response if the search string was found, otherwise and empty string is returned.

command

(
  • cmd
)

Send an AT command and ignore any response.

Parameters:

  • cmd String

    The AT command to send, including the "AT" prefix and a terminating carriage return ("\r").

stringCR2LF

(
  • str
)
String

This is a convenience method that converts each CR () in a string to a LF (
) and returns it. This is useful for outputting the response to an AT command for instance, which is often CR terminated.

Parameters:

  • str String

    The string to convert

Returns:

String:

The converted string

setFlowControl

(
  • fc
)

Set a flow control method for the UART. By default, during initialization, flow control is disabled.

Parameters:

  • fc UARTAT_FLOW_CONTROL_T

    One of the UARTAT_FLOW_CONTROL_T values.

find

(
  • buffer
  • str
)
Boolean

Look for a string in a buffer. This is a utility function that can be used to indicate if a given string is present in a supplied buffer. The search is case sensitive.

Parameters:

  • buffer String

    The string buffer in which to search.

  • str String

    The string to search for.

Returns:

Boolean:

true if the string was found, false otherwise.

filterCR

(
  • enable
)

Filter out carriage returns (CR) from response buffers if enabled. This operates only on the response buffers returned from commandWithResponse() , command() , and commandWaitfor().

Parameters:

  • enable Boolean

    true to filter out CR's, false otherwise