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• Why do we need the new Async AsyncHTTPRequest_Teensy41 library
  • Features
  • Supports
  • Principles of operation
  • Currently supported Boards
• Changelog
• Prerequisites
• Installation
  • Use Arduino Library Manager
  • Manual Install
  • VS Code & PlatformIO
• Packages' Patches
  • 1. For Teensy boards
• HOWTO FixMultiple Definitions Linker Error
• Examples
  • 1. AsyncCustomHeader
  • 2. AsyncDweetGet
  • 3. AsyncDweetPost
  • 4. AsyncHTTPRequest
  • 5. AsyncSimpleGET
  • 6. multiFileProject
• Example AsyncHTTPRequest
  • 1. File AsyncHTTPRequest.ino
  • 2. File defines.h
• Debug Terminal Output Samples
  • 1. AsyncHTTPRequest on TEENSY 4.1
  • 2. AsyncCustomHeader on TEENSY 4.1
  • 3. AsyncDweetGET on TEENSY 4.1
  • 4. AsyncDweetPOST on TEENSY 4.1
  • 5. AsyncSimpleGET on TEENSY 4.1
• Debug
• Troubleshooting
• Issues
• TO DO
• DONE
• Contributions and Thanks
• Contributing
• License and credits
• Copyright

1. Asynchronous HTTP Request library forTeensy 4.1 using built-in QNEthernet
2. Providing a subset of HTTP.
3. Relying onTeensy41_AsyncTCP library
4. Methods similar in format and usage to XmlHTTPrequest in Javascript.

1. GET, POST, PUT, PATCH, DELETE and HEAD
2. Request and response headers
3. Chunked response
4. Single String response for short (<~5K) responses (heap permitting).
5. Optional onData callback.
6. Optional onReadyStatechange callback.

This library adds a simple HTTP layer on top of theTeensy41_AsyncTCP library tofacilitate REST communication from a Client to a Server. The paradigm is similar to theXMLHttpRequest in Javascript, employing the notion of a ready-state progression through the transaction request.

Synchronization can be accomplished using callbacks on ready-state change, a callback on data receipt, or simply polling for ready-state change. Data retrieval can be incremental as received, or bulk retrieved when the transaction completes provided there is enough heap to buffer the entire response.

The underlying buffering uses a newxbuf class. It handles both character and binary data. Classxbuf uses a chain of small (64 byte) segments that are allocated and added to the tail as data is added and de-allocated from the head as data is read, achieving the same result as a dynamic circular buffer, limited only by the size of heap. Thexbuf implementsindexOf andreadUntil functions.

For short transactions, buffer space should not be an issue. In fact, it can be more economical than other methods that use larger fixed length buffers. Data is acked when retrieved by the caller, so there is some limited flow control to limit heap usage for larger transfers.

Request and response headers are handled in the typical fashion.

Chunked responses are recognized and handledtransparently.

This library is based on, modified from:

1. Bob Lemaire's asyncHTTPrequest Library

1. Teensy 4.1 using QNEthernet Library

1. Arduino IDE 1.8.19+ for Arduino.
2. Teensy core v1.57+ for Teensy 4.1.
3. QNEthernet Library version v0.17.0+ for Teensy 4.1 built-in Ethernet.
4. Teensy41_AsyncTCP library v1.1.0+ to useTeensy 4.1 using QNEthernet Library. To install, check

The best and easiest way is to useArduino Library Manager. Search forAsyncHTTPRequest_Teensy41, then select / install the latest version. You can also use this link for more detailed instructions.

1. Navigate toAsyncHTTPRequest_Teensy41 page.
2. Download the latest releaseAsyncHTTPRequest_Teensy41-main.zip.
3. Extract the zip file toAsyncHTTPRequest_Teensy41-main directory
4. Copy the wholeAsyncHTTPRequest_Teensy41-main folder to Arduino libraries' directory such as~/Arduino/libraries/.

1. InstallVS Code
2. InstallPlatformIO
3. InstallAsyncHTTPRequest_Teensy41 library by usingLibrary Manager. Search for AsyncHTTPRequest_Teensy41 inPlatform.io Author's Libraries
4. Use includedplatformio.ini file from examples to ensure that all dependent libraries will installed automatically. Please visit documentation for the other options and examples atProject Configuration File

To be able to compile and run on Teensy boards, you have to copy the files inPackages_Patches for Teensy directory into Teensy hardware directory (./arduino-1.8.19/hardware/teensy/avr/boards.txt).

Supposing the Arduino version is 1.8.19. These files must be copied into the directory:

• ./arduino-1.8.19/hardware/teensy/avr/boards.txt
• ./arduino-1.8.19/hardware/teensy/avr/cores/teensy/Stream.h
• ./arduino-1.8.19/hardware/teensy/avr/cores/teensy3/Stream.h
• ./arduino-1.8.19/hardware/teensy/avr/cores/teensy4/Stream.h

Whenever a new version is installed, remember to copy this file into the new version directory. For example, new version is x.yy.zzThese files must be copied into the directory:

• ./arduino-x.yy.zz/hardware/teensy/avr/boards.txt
• ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy/Stream.h
• ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy3/Stream.h
• ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy4/Stream.h

The current library implementation, usingxyz-Impl.h instead of standardxyz.cpp, possibly creates certainMultiple Definitions Linker error in certain use cases.

You can include this.hpp file

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error#include"AsyncHTTPRequest_Teensy41.hpp"//https://github.com/khoih-prog/AsyncHTTPRequest_Teensy41

in many files. But be sure to use the following.h filein just 1.h,.cpp or.ino file, which mustnot be included in any other file, to avoidMultiple Definitions Linker Error

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error#include"AsyncHTTPRequest_Teensy41.h"//https://github.com/khoih-prog/AsyncHTTPRequest_Teensy41

Check the newmultiFileProject example for aHOWTO demo.

Have a look at the discussion inDifferent behaviour using the src_cpp or src_h lib #80

1. AsyncCustomHeader
2. AsyncDweetGet
3. AsyncDweetPost
4. AsyncHTTPRequest
5. AsyncSimpleGET
6. multiFileProject

Start AsyncHTTPRequest on TEENSY4.1AsyncHTTPRequest_Teensy41 v1.10.0Initialize Ethernetusing DHCP => Connected! IP address:192.168.2.107**************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:54:16.675525-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227256utc_datetime:2023-02-01T04:54:16.675525+00:00utc_offset: -05:00week_number:5****************************************************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:55:16.675337-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227316utc_datetime:2023-02-01T04:55:16.675337+00:00utc_offset: -05:00week_number:5**************************************

Start AsyncCustomHeader on TEENSY4.1AsyncHTTPRequest_Teensy41 v1.10.0Initialize Ethernetusing DHCP => Connected! IP address:192.168.2.107Sending GET Request to http://worldtimeapi.org/api/timezone/America/Toronto.txt**************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:56:16.674942-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227376utc_datetime:2023-02-01T04:56:16.674942+00:00utc_offset: -05:00week_number:5**************************************Sending GET Request to http://worldtimeapi.org/api/timezone/America/Toronto.txt**************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:57:16.675848-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227436utc_datetime:2023-02-01T04:57:16.675848+00:00utc_offset: -05:00week_number:5**************************************

Start AsyncDweetGET on TEENSY4.1AsyncHTTPRequest_Teensy41 v1.10.0Initialize Ethernetusing DHCP => Connected! IP address:192.168.2.107**************************************{"this":"succeeded","by":"dweeting","the":"dweet","with":{"thing":"currentSecond","created":"2022-03-18T19:51:49.407Z","content":{"second":66},"transaction":"4dcdcae9-ace0-4767-86d0-6b830fd3fc05"}}**************************************"second":66Value string:66Actual value:66

Start AsyncDweetPOST on TEENSY4.1AsyncHTTPRequest_Teensy41 v1.10.0Initialize Ethernetusing DHCP => Connected! IP address:192.168.2.107Makingnew POST request**************************************{"this":"succeeded","by":"dweeting","the":"dweet","with":{"thing":"pinA0-Read","created":"2022-03-18T19:57:17.768Z","content":{"sensorValue":1007},"transaction":"76940001-4d31-4995-a712-189d9d874cb1"}}**************************************"sensorValue":1007Value string:1007Actual value:1007

Start AsyncSimpleGET on TEENSY4.1AsyncHTTPRequest_Teensy41 v1.10.0Initialize Ethernetusing DHCP => Connected! IP address:192.168.2.107**************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:58:16.676610-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227496utc_datetime:2023-02-01T04:58:16.676610+00:00utc_offset: -05:00week_number:5****************************************************************************abbreviation: ESTclient_ip: aaa.bbb.ccc.ddddatetime:2023-01-31T23:59:16.675139-05:00day_of_week:2day_of_year:31dst:falsedst_from: dst_offset:0dst_until: raw_offset: -18000timezone: America/Torontounixtime:1675227556utc_datetime:2023-02-01T04:59:16.675139+00:00utc_offset: -05:00week_number:5**************************************

Debug is enabled by default on Serial.

You can also change the debugging level from 0 to 4

#defineASYNC_HTTP_DEBUG_PORT           Serial// Use from 0 to 4. Higher number, more debugging messages and memory usage.#define_ASYNC_HTTP_LOGLEVEL_1

If you get compilation errors, more often than not, you may need to install a newer version of theESP32 / ESP8266 / STM32 core for Arduino.

Sometimes, the library will only work if you update theTeensy core to the latest version because I am using newly added functions.

Submit issues to:AsyncHTTPRequest_Teensy41 issues

1. Fix bug. Add enhancement
2. Add many more examples.

1. Initial porting and coding forTeensy 4.1 using built-in QNEthernet
2. Add debugging features.
3. Add PUT, PATCH, DELETE and HEAD besides GET and POST.
4. Optimize library code by usingreference-passing instead ofvalue-passing
5. Fix long timeout if usingIPAddress
6. Display only successful responseText in examples
7. Improve debug messages by adding functions to display error messages instead ofcryptic error number
8. Not try to reconnect to the samehost:port after connected
9. Fix bug of wrongreqStates
10. Default to reconnect to the samehost:port after connected for new HTTP sites.
11. Useallman astyle and addutils
12. Fix_parseURL() bug. CheckBug with _parseURL() #21
13. ImproveREADME.md so that links can be used in other sites, such asPIO

This library is based on, modified, bug-fixed and improved from:

1. Bob Lemaire'sasyncHTTPrequest Library to use the betterasynchronous features of these following Async TCP Libraries : (ESPAsyncTCP,AsyncTCP, andTeensy41_AsyncTCP )

⭐️ Bob Lemaire

If you want to contribute to this project:

• Report bugs and errors
• Ask for enhancements
• Create issues and pull requests
• Tell other people about this library

• The library is licensed underGPLv3

Copyright (C) <2018> <Bob Lemaire, IoTaWatt, Inc.>

Copyright (C) <2022-> Khoi Hoang