Parsing using the ArduinoJson library

Question

I am trying to parse JSON using the ArduinoJson library. The problem is that I can’t parse www.read() because it’s declared as a char. I think www.read() needs to be a string? How can I convert www.read() into a format that jsonBufffer.parseObject() can understand? Please excuse any lack of terminology. I am new to using JSON.

When I run the code I get to the point where it prints "-------------------------------------" then it does nothing.

#include <Adafruit_CC3000.h>
#include <ccspi.h>
#include <SPI.h>
#include <string.h>
#include "utility/debug.h"
#include <ArduinoJson.h>
// These are the interrupt and control pins
#define ADAFRUIT_CC3000_IRQ 3 // MUST be an interrupt pin!
// These can be any two pins
#define ADAFRUIT_CC3000_VBAT 5
#define ADAFRUIT_CC3000_CS 10
// Use hardware SPI for the remaining pins
// On an UNO, SCK = 13, MISO = 12, and MOSI = 11
Adafruit_CC3000 cc3000 = Adafruit_CC3000(ADAFRUIT_CC3000_CS, 
ADAFRUIT_CC3000_IRQ, ADAFRUIT_CC3000_VBAT,
SPI_CLOCK_DIVIDER); // you can change this clock speed
#define WLAN_SSID "WLAN_SSID_HERE" // cannot be longer than 32 characters!
#define WLAN_PASS "WLAN_PASS_HERE"
// Security can be WLAN_SEC_UNSEC, WLAN_SEC_WEP, WLAN_SEC_WPA or WLAN_SEC_WPA2
#define WLAN_SECURITY WLAN_SEC_WPA2
#define IDLE_TIMEOUT_MS 300000 // Amount of time to wait (in milliseconds) with no data 
// received before closing the connection. If you know the server
// you're accessing is quick to respond, you can reduce this value.
// What page to grab!
#define WEBSITE "wefeel.csiro.au"
#define WEBPAGE "/api/emotions/primary/totals"
StaticJsonBuffer<200> jsonBuffer;
uint32_t ip;
void setup(void)
{
 Serial.begin(115200);
 Serial.println(F("Hello, CC3000!\n")); 
 /* Initialise the module */
 Serial.println(F("\nInitializing..."));
 if (!cc3000.begin())
 {
 Serial.println(F("Couldn't begin()! Check your wiring?"));
 while(1);
 }
 Serial.print(F("\nAttempting to connect to ")); 
 Serial.println(WLAN_SSID);
 if (!cc3000.connectToAP(WLAN_SSID, WLAN_PASS, WLAN_SECURITY)) {
 Serial.println(F("Failed!"));
 while(1);
 }
 Serial.println(F("Connected!"));
 /* Wait for DHCP to complete */
 Serial.println(F("Request DHCP"));
 while (!cc3000.checkDHCP())
 {
 delay(100); // ToDo: Insert a DHCP timeout!
 } 
 /* Display the IP address DNS, Gateway, etc. */
// while (! displayConnectionDetails()) {
 // delay(1000);
// }
 ip = 0;
 // Try looking up the website's IP address
 Serial.print(WEBSITE); 
 Serial.print(F(" -> "));
 while (ip == 0) {
 if (! cc3000.getHostByName(WEBSITE, &ip)) {
 Serial.println(F("Couldn't resolve!"));
 }
 delay(500);
 }
 cc3000.printIPdotsRev(ip);
}
void loop(void)
{
 char c;
 Adafruit_CC3000_Client www = cc3000.connectTCP(ip, 80);
 delay(300);
 if (www.connected()) {
 www.fastrprint(F("GET "));
 www.fastrprint(WEBPAGE);
 www.fastrprint(F(" HTTP/1.1\r\n"));
 www.fastrprint(F("Host: ")); 
 www.fastrprint(WEBSITE); 
 www.fastrprint(F("\r\n"));
 www.fastrprint(F("\r\n"));
 www.println();
 } 
 else {
 Serial.println(F("Connection failed")); 
 return;
 }
 Serial.println(F("-------------------------------------"));
 unsigned long lastRead = millis();
 while (www.connected() && (millis() - lastRead < IDLE_TIMEOUT_MS)) {
 //Serial.print(www.available());
 while (www.available()) {
 
 
 //Serial.print(c);
 //char json[] = www.read();
 }
 } 
 c = www.read();
 Serial.print(c);
 JsonObject& root = jsonBuffer.parseObject((char*)c);
 if (!root.success()) {
 Serial.println("parseObject() failed");
 return;
 }
 long love = root["love"];
 long other = root["other"];
 long sadness = root["sadness"];
 long anger = root["anger"];
 long joy = root["joy"];
 long surprise = root["surprise"];
 long fear = root["fear"];
 Serial.println(love);
 Serial.println(other);
 Serial.println(sadness);
 Serial.println(anger);
 Serial.println(joy);
 Serial.println(surprise);
 Serial.println(fear);
 www.stop();
 delay(100);
 www.close();
 delay(200);
 }

• hcheung: First you never setup the HTTP header with "Content-Type: application/json", so the data return might not be in json as you want. Secondly, you need to create a buffer to store the response back from the server within the while(www.available()) { buffer[i++]=www.read(); } (i.e. read the data char by char and store in the buffer), then you can parse the return data in the buffer with JsonObject& root=jsonBuffer.parseObject(buffer);.

Answer 1

There are two read methods. One that returns a single character (or error), and one that populates a buffer; you want the latter, with method signature int read(char* buf, size_t len) or some such. Read the source.

When allocating the json buffer in StaticJsonBuffer<200> jsonBuffer; , make sure your expected json data fit in 200 bytes.

• Balockeh22: Thank you for responding to my problem. I'm assuming you would use jsonBuffer as uint8_t *buf but what value do I use for size_t len?
• JayEye: no, jsonBuffer has to still be a StaticJsonBuffer. It's what you read() into that should change. Something along the lines of: char buf[256]; size_t n_read = www.read(buf, 255); buf[n_read] = '0円'; You need the third line because parseObject expects a nul-terminated string.
• Balockeh22: I really appreciate your help. I think Im following you but am still unclear what I need to do next. Im thinking it is calling jsonBuffer.ParseObject but I was thinking that I would have it parse n_read which seems to be incorrect? What variable should I perform the parse on?