Getting all data of my JSON object from Serial.read() at once

Question

I'm new to Arduino and I'm building a project that fetches data from a website (using ESP8266) and then transfers them to my Arduino UNO via serial port.

Data coming from ESP8266 every 20s - [{"x": 0,"y": 0,"rgb": [255, 200, 174]},{"x": 1,"y": 0,"rgb": [255, 200, 174]},{"x": 2,"y": 0,"rgb": [255, 200, 174]}]

But when I print the data like this


void loop() {
if (Serial.available()) {
    Serial.write(Serial.read()); // This line prints only one character out of whole string
data =  Serial.read(); // so this doesn't work

DeserializationError error = deserializeJson(response, data);
if (error) {
  Serial.print(F(&quot;deserializeJson() failed: &quot;));
  Serial.println(error.f_str());
  return;
}
for (JsonObject elem : response.as&lt;JsonArray&gt;()) {
  int x = elem[&quot;x&quot;]; // 2, 2, 2
  int y = elem[&quot;y&quot;]; // 2, 2, 2
  JsonArray rgb = elem[&quot;rgb&quot;];

  int rgb_0 = rgb[0]; // 255, 255, 255
  int rgb_1 = rgb[1]; // 255, 255, 255
  int rgb_2 = rgb[2]; // 255, 255, 255
  //Serial.print(x);
}

}
  delay(1000);   //then it waits 1 second and goes from the start
}

How can I make it to get the whole string and save it into a variable?

Thanks, much for answering.

timemage · Accepted Answer · 2021-05-22T16:26:17.057

I was going to put this as a comment, but maybe it belongs as an answer:

For what it's worth, ArduinoJSON seems to be able to deserialize directly from a stream, i.e. Serial, which may obviate the question as asked. Presumably it knows where to stop deserializing, because it knows when it has received an entire JSON object; being a proper JSON parser, it can probably work this out better than you can without, you know, writing a JSON parser.

The following was just thrown together, now the author is here you should probably just follow their direction, but here's the code anyway:

#include <ArduinoJson.h>
void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(9600);
  Serial.setTimeout(30000);
}
void print_transmission_counter( {
    static unsigned long received_object_counter;
    Serial.println(F("\n\n\n\n"));
    for (int i = 0; i < 30; ++i) {
        Serial.write('-');
    }
    Serial.write('[');
    Serial.print(received_object_counter++);
    Serial.println(']');
}
void loop() {
    static StaticJsonDocument<256> json_doc;
    static bool led_state;
print_transmission_counter();

const auto deser_err = deserializeJson(json_doc, Serial);
if (deser_err) {
    Serial.print(F(&quot;Failed to deserialize, reason: \&quot;&quot;));
    Serial.print(deser_err.c_str());
    Serial.println('&quot;');
} else  {
    Serial.print(F(&quot;Recevied valid json document with &quot;));
    Serial.print(json_doc.size());
    Serial.println(F(&quot; elements.&quot;));
    Serial.println(F(&quot;Pretty printed back at you:&quot;));
    serializeJsonPretty(json_doc, Serial);
    Serial.println();
}


// Just give some visual indication that the loop is progressing
led_state = !led_state;
digitalWrite(LED_BUILTIN, led_state);

}
//  vim:sw=2:ts=2:et:nowrap:ft=cpp:

Getting all data of my JSON object from Serial.read() at once

1 Answers1