[WIZwiki_W7500ECO] HTTPClient with JSON parser

JSON is easy for machines to parse and generate which is based on a subset of the JavaScript Programming Language. Currently many Web Services allow to access data in JSON format. However, JSON parser is too big for low-end device as like a ARMmbed platform which has limited-resource. This post shows how to use HTTPClient parse Json data in ARMmbed platform.
//embedr.flickr.com/assets/client-code.js

Preparation materials

1. Software

* JSON Parser: MbedJSONValue libs
* Ethernet Networking : WIZnetInterface
* HTTP Server with JSON : Fraka6 Blog – No Free Lunch: The simplest python server example 😉
2. Hardware
* WIZwiki-W7500ECONET: WIZwiki-W7500 + ECO Shield Ethernet
//embedr.flickr.com/assets/client-code.js

• ARMmbed Board: WIZwiki-W7500ECO
  //embedr.flickr.com/assets/client-code.js

• Ethernet Shield: ECO Shield Ethernet
  //embedr.flickr.com/assets/client-code.js

Simplest python JSON server on PC

• Reference : fraka6.blogsopot.kr: The simplest python server example

• Modify Server IP address & port on ron_handler

def run(port=8000): #set port

print('http server is starting...')
#ip and port of server
#server_address = ('127.0.0.1', port)
server_address = ('192.168.0.223', port)#set port
httpd = HTTPServer(server_address, Handler)
print('http server is running...listening on port %s' %port)
httpd.serve_forever()

• Modify JSON form in do_GET handler

#handle GET command
def do_GET(self):
if format == 'html':
self.send_response(200)
self.send_header("Content-type", "text/plain")
self.send_header('Content-type','text-html')
self.end_headers()
self.wfile.write("body")
elif format == 'json':
#self.request.sendall(json.dumps({'path':self.path}))
#self.request.sendall(json.dumps({'pi':3.14}))
self.request.sendall(json.dumps({'name':'John snow', 'age': 30, 'gender':'male'}))
else:
self.request.sendall("%s\t%s" %('path', self.path))
return

• Excute json_server
  //embedr.flickr.com/assets/client-code.js

• Test by using curl
  $>curl ip_address:port_number
  //embedr.flickr.com/assets/client-code.js

Make main.cc

• Source Code@https://developer.mbed.org/users/embeddist/code/Simple_HTTPClient_JSON/wiki/Homepage

• Network Configration for WIZwiki-W7500ECO

// Enter a MAC address for your controller below.
uint8_t mac_addr[6] = {0x00, 0x08, 0xDC, 0x00, 0x01, 0x02};

printf("initializing Ethernet\r\n");
// initializing MAC address
eth.init(mac_addr, "192.168.0.34", "255.255.255.0", "192.168.0.1");

// Check Ethenret Link
if(eth.link() == true) printf("- Ethernet PHY Link-Done \r\n");
else printf("- Ethernet PHY Link- Fail\r\n");

// Start Ethernet connecting: Trying to get an IP address using DHCP
if (eth.connect() 0) {
http_rx_msg[returnCode] = '\0';
printf("Received %d chars from server:\n\r%s\n", returnCode, http_rx_msg);
}

• Do JSON parse

parse(parser, http_rx_msg);

• Output the parsed data

// parsing "string" in string type
printf("name =%s\r\n" , parser["name"].get().c_str());
// parsing "age" in integer type
printf("age =%d\r\n" , parser["age"].get());
// parsing "gender" in string type
printf("gender =%s\r\n" , parser["gender"].get().c_str());

Demo. HTTPClient with JSON parser

1. Network config.
2. Confirm Received JSON data
3. Print-out the pasing data
   //embedr.flickr.com/assets/client-code.js

Packet Capture

1. TCP-Connection
2. Target board sends GET Form to simple python JSON server
3. simple python JSON server sends JSON data to Target board
   //embedr.flickr.com/assets/client-code.js

WIZnetInterface for ARMmbed

This is WIZnet Ethernet Interface using Hardware TCP/IP chip, W5500 and TCP/IP Offload Engine, W7500.
Users » embeddist » Code » WIZnetInterface
-> WIZnetInterface Lib will be released on Team WIZnet

• WIZwiki_W7500
  • Platforms » WIZwiki-W7500
    
• W5500 Ethernet Shield
  • Components » Communication » Ethernet » W5500 Ethernet Kit for IoT
    

This is an Ethernet Interface library port-based on EthernetInterface. This is where the driver using TCP/IP offload(W5500/W7500), which is a market-proven hardwired TCP/IP stack, is implemented. Therefore, this library does not need lwip-eth.library.

• The Socket folder contains files that implement the SocketAPI and Protocols as like DHCP and DNS.
• The arch folder contains files that implement the driver for W5500 and W7500x_TOE.
• The EthernetInterface.c/.h implement the functions from SocketAPI/EthernetInterface.h
• The eth_arch.h implement to select TCP/IP TOE depending on platform.

What is new?

• eth_arch.h
  The eth_arch.h file is added to select arch depending to Target platform, we used define of TARGET_platform.

#if defined(TARGET_WIZwiki_W7500)
#include "W7500x_toe.h"
#define __DEF_USED_IC101AG__  //For using IC+101AG@WIZwiki-W7500
#else
#include "W5500.h"            // W5500 Ethernet Shield 
//#define USE_WIZ550IO_MAC    // WIZ550io; using the MAC address
#endif

• link()
  The link function is added to check Ethernet link (PHY) up or not.

    * Check if an ethernet link is pressent or not.
    *
    * @returns true if successful
    */
    bool link(int wait_time_ms= 3*1000);

• link_set()
  The set_link function is added to check Ethernet link (PHY) up or not.

   /*
    * Sets the speed and duplex parameters of an ethernet link.
    *
    * @returns true if successful
    */
    void set_link(PHYMode phymode);

• Included DHCP and DNS lib
  DHCP and DNS lib moved in Socket folder.
  

How to import

• import and update
  • Right Click and click ‘From Import Wizard’ to import WIZnetInterface Library
    
  • In import Wizard, input ‘WIZnetInterfae” in search box and click ‘Search’ button. Click ‘WIZnetInterface’ in search result window and click ‘Import’ button.
    
  • Set ‘Import name’ and ‘Target path’, check ‘update’
    

Where is Clone repository

hg clone https://embeddist@developer.mbed.org/users/embeddist/code/WIZnetInterface/

How to use

• make main.cpp
  • WIZwiki_W7500

  #define _DHCP_
  EthernetInterface eth;  /*1. Creat eth object from EthernetInteface class*/
  
  main()
  {
      uint8_t mac_addr[6] = {0x00, 0x08, 0xDC, 0x01, 0x02, 0x03};  
  
      /*2. Set MAC, IP, Gatway address and Subnet Mask*/
  #ifdef _DHCP_
      /*2.1 Set  MAC address, Initialize the interface with DHCP*/
      eth.init(mac_addr); 
  #else   
      /*2.2 Set  MAC address and Set MAC, IP, Gatway address and Subnet Mask*/
      eth.init(mac_addr, "192.168.77.34", "255.255.255.0", "192.168.77.1"); 
  #endif
  
      /*3. Check Ethernet Link-Done */
      printf("Check Ethernet Link\r\n");
      if(eth.link() == true) { printf("- Ethernet PHY Link-Done \r\n"); }
      else {printf("- Ethernet PHY Link- Fail\r\n");}
  
      /*4. Set IP addresses ,start DHCP if needed  */
      eth.connect();
      printf("Connected, IP: %s\n\r", eth.getIPAddress());
      printf("MASK: %s\n\r", eth.getNetworkMask());
      printf("GW: %s\n\r",eth.getGateway());
      ...
  
      /* Your application 
         Visit for examples - https://developer.mbed.org/teams/WIZnet/
      */
  
  }
  

  • W5500 Ethernet Shield

  #define _DHCP_
  /* 0. Set SPI Interface with SPI API*/
  SPI spi(D11, D12, D13);                  // mosi, miso, sclk
  /*1. Creat eth object from EthernetInteface class*/
  EthernetInterface eth(&spi, D10, D9);    // spi, cs, reset
  
  main()
  {
      uint8_t mac_addr[6] = {0x00, 0x08, 0xDC, 0x1D, 0x62, 0x11}; 
      /*2. Set MAC, IP, Gatway address and Subnet Mask*/
  #ifdef _DHCP_
      /*2.1 Set  MAC address, Initialize the interface with DHCP*/
      eth.init(mac_addr); 
  #else
      /*2.2 Set  MAC address and Set MAC, IP, Gatway address and Subnet Mask */
      eth.init(mac_addr, "192.168.77.34", "255.255.255.0", "192.168.77.1"); 
  #endif
  
      /*3. Check Ethernet Link-Done */
      printf("Check Ethernet Link\r\n");
      if(eth.link() == true) { printf("- Ethernet PHY Link-Done \r\n"); }
      else {printf("- Ethernet PHY Link- Fail\r\n");}
  
      /*4. Set IP addresses ,start DHCP if needed  */
      eth.connect();
      printf("Connected, IP: %s\n\r", eth.getIPAddress());
      printf("MASK: %s\n\r", eth.getNetworkMask());
      printf("GW: %s\n\r",eth.getGateway());
      ...
  
      /* Your application 
         Visit for examples - https://developer.mbed.org/teams/WIZnet/
      */
  
  }
  

WIZnetInterface Implementations for mbed Ethenret Interface

For networking based on Ethernet network, Ethenret Interface library is provided and is composed TCP/IP Protocol layer, Ethernet, EthernetInterface and Socket. In other words, the EthernetInterface library includes the networking stack necessary for connect betwwen mbed platform and Internet.

Each layer in EthernetInterface provides APIs to connect to the internet.
* EthernetInterfaec : https://developer.mbed.org/handbook/Ethernet-Interface
* Socket : https://developer.mbed.org/handbook/Socket
* TCP/IP Protocols : https://developer.mbed.org/handbook/TCP-IP-protocols-and-APIs
* Ethernet : https://developer.mbed.org/handbook/Ethernet

WIZnetInterface Implementation base on mbed Ethernet Interface

• EthernetInterface- EthernetInterface Class
  

  Type	Func.	Descriptions	WIZnetInterface Support
  static int	init ()	Initialize the interface with DHCP.	O
  static int	init (const char *ip, const char *mask, const char *gateway)	Initialize the interface with a static IP address.	O
  static int	connect (unsigned int timeout_ms=15000)	Connect Bring the interface up, start DHCP if needed.	O
  static int	disconnect ()	Disconnect Bring the interface down.	X
  static char*	getMACAddress ()	Get the MAC address of your Ethernet interface.	O
  static char*	getIPAddress ()	Get the IP address of your Ethernet interface.	O
  static char*	getGateway ()	Get the Gateway address of your Ethernet interface.	O
  static char*	getNetworkMask ()	Get the Network mask of your Ethernet interface.	O
  void	EthernetInterface (PinName mosi, PinName miso, PinName sclk, PinName cs, PinName reset)	Initialize SPI SPI pins to user for SPI interface and Reset pin for W5500	0 (for W5500)
  void	EthernetInterface (SPI* spi, PinName cs, PinName reset)	Initialize SPI SPI pins to user for SPI interface and Reset pin for W5500	O (for W5500)

• Socket – TCPSocketServer Class

  Type	Func.	Descriptions	WIZnetInterface Support
  	TCPSocketServer ()	Instantiate a TCP Server.	O
  int	bind (int port)	Bind a socket to a specific port.	O
  int	listen (int backlog=1)	Start listening for incoming connections.	O
  int	accept ( TCPSocketConnection &connection)	Accept a new connection.	O
  void	set_blocking (bool blocking, unsigned int timeout=1500)	Set blocking or non-blocking mode of the socket and a timeout on blocking socket operations.	O
  int	set_option (int level, int optname, const void *optval, socklen_t optlen)	Set socket options.	X
  int	get_option (int level, int optname, void *optval, socklen_t *optlen)	Get socket options.	X
  int	close (bool shutdown=true)	Get socket options.	O

• Socket – TCPSocketConnection Class

  Type	Func.	Descriptions	WIZnetInterface Support
  	TCPSocketConnection ()	TCP socket connection.	O
  int	connect (const char *host, const int port)	Connects this TCP socket to the server.	O
  bool	is_connected (void)	Check if the socket is connected.	O
  int	send (char *data, int length)	Send data to the remote host.	O
  int	send_all (char *data, int length)	Send all the data to the remote host.	O
  int	receive (char *data, int length)	Receive data from the remote host.	O
  int	receive_all (char *data, int length)	Receive all the data from the remote host.	O
  void	set_blocking (bool blocking, unsigned int timeout=1500)	Set blocking or non-blocking mode of the socket and a timeout on blocking socket operations.	O
  int	set_option (int level, int optname, const void *optval, socklen_t optlen)	Set socket options.	X
  int	get_option (int level, int optname, void *optval, socklen_t *optlen)	Get socket options.	X
  int	close (bool shutdown=true)	Close the socket.	O
  void	reset_address (void)	Reset the address of this endpoint.	O
  int	set_address (const char *host, const int port)	Set the address of this endpoint.	O
  char*	get_address (void)	Get the IP address of this endpoint.	O
  int	get_port (void)	Get the port of this endpoint.	O

• etnerhet_api – ethernet_api Class

  Type	Func.	Descriptions	WIZnetInterface Support
  	Ethernet ()	Initialise the ethernet interface.	X
  virtual	~Ethernet ()	Powers the hardware down.	X
  int	write (const char *data, int size)	Writes into an outgoing ethernet packet.	X
  int	send ()	Send an outgoing ethernet packet.	X
  int	receive ()	Recevies an arrived ethernet packet.	X
  int	read (const char *data, int size)	Read from an recevied ethernet packet.	X
  void	address (char *mac)	Gives the ethernet address of the mbed.	X
  int	link()	Returns if an ethernet link is pressent or not.	O
  void	set_link(Mode mode)	Sets the speed and duplex parameters of an ethernet link.	O

##Revision History
* Initial Release : 19 June. 2015