【IoT】LTE-M Shield for ArduinoでUDP送信し、消費電力量と通信量を低減する方法

void loop() {
  long uptime_sec = millis() / 1000;

  char payload[120];
  sprintf_P(payload, PSTR("{\"uptime\":%lu}"), uptime_sec);
  CONSOLE.println(payload);

  /* connect */
  if (!ctx.connect(ENDPOINT, 80)) {
    CONSOLE.println(F("failed."));
    delay(3000);
    return;
  }
  /* send request */
  char hdr_buf[40];
  ctx.println(F("POST / HTTP/1.1"));
  sprintf_P(hdr_buf, PSTR("Host: %s"), ENDPOINT);
  ctx.println(hdr_buf);
  ctx.println(F("Content-Type: application/json"));
  sprintf_P(hdr_buf, PSTR("Content-Length: %d"), strlen(payload));
  ctx.println(hdr_buf);
  ctx.println();
  ctx.println(payload);
  /* receive response */
  while (ctx.connected()) {
    String line = ctx.readStringUntil('\n');
    CONSOLE.println(line);
    if (line == "\r") {
      CONSOLE.println(F("Response header received."));
      break;
    }
  }
  // NOTE: response body is ignore
  ctx.stop();

  delay(INTERVAL_MS);
}

  bool modemConnect(const char *host, uint16_t port, uint8_t mux,
                    bool ssl = false, int timeout_s = 150)
  {
    if (ssl)
    {
      DBG("SSL not yet supported on this module!");
    }

    uint32_t timeout_ms = ((uint32_t)timeout_s) * 1000;

    // <PDPcontextID>(1-16), <connectID>(0-11),
    // "TCP/UDP/TCP LISTENER/UDPSERVICE", "<IP_address>/<domain_name>",
    // <remote_port>,<local_port>,<access_mode>(0-2; 0=buffer)
    sendAT(GF("+QIOPEN=1,"), mux, GF(",\""), GF("TCP"), GF("\",\""), host,
           GF("\","), port, GF(",0,0"));
    waitResponse();

    if (waitResponse(timeout_ms, GF(GSM_NL "+QIOPEN:")) != 1)
    {
      return false;
    }

    if (streamGetIntBefore(',') != mux)
    {
      return false;
    }
    // Read status
    return (0 == streamGetIntBefore('\n'));
  }

#define CONSOLE Serial
#define INTERVAL_MS (60000)
#define ENDPOINT "uni.soracom.io"
#define SKETCH_NAME "send_uptime_with_soracom_UDP"
#define VERSION "1.0"

/* for LTE-M Shield for Arduino */
#define RX 10
#define TX 11
#define BAUDRATE 9600
#define BG96_RESET 15

#define TINY_GSM_MODEM_BG96
#include <TinyGsmClient.h>

#include <SoftwareSerial.h>
SoftwareSerial LTE_M_shieldUART(RX, TX);
TinyGsm modem(LTE_M_shieldUART);
TinyGsmClient ctx(modem);

void setup() {
  CONSOLE.begin(115200);

  CONSOLE.println();
  CONSOLE.print(F("Welcome to ")); CONSOLE.print(SKETCH_NAME); CONSOLE.print(F(" ")); CONSOLE.println(VERSION);

  CONSOLE.print(F("resetting module "));
  pinMode(BG96_RESET,OUTPUT);
  digitalWrite(BG96_RESET,LOW);
  delay(300);
  digitalWrite(BG96_RESET,HIGH);
  delay(300);
  digitalWrite(BG96_RESET,LOW);
  CONSOLE.println(F(" done."));

  LTE_M_shieldUART.begin(BAUDRATE);

  CONSOLE.print(F("modem.restart()"));
  modem.restart();
  CONSOLE.println(F(" done."));

  CONSOLE.print(F("modem.getModemInfo(): "));
  String modemInfo = modem.getModemInfo();
  CONSOLE.println(modemInfo);

  CONSOLE.print(F("waitForNetwork()"));
  while (!modem.waitForNetwork()) CONSOLE.print(".");
  CONSOLE.println(F(" Ok."));

  CONSOLE.print(F("gprsConnect(soracom.io)"));
  modem.gprsConnect("soracom.io", "sora", "sora");
  CONSOLE.println(F(" done."));

  CONSOLE.print(F("isNetworkConnected()"));
  while (!modem.isNetworkConnected()) CONSOLE.print(".");
  CONSOLE.println(F(" Ok."));

  CONSOLE.print(F("My IP addr: "));
  IPAddress ipaddr = modem.localIP();
  CONSOLE.println(ipaddr);
}

void loop() {
  long uptime_sec = millis() / 1000;

  // バイナリ形式の送信データ作成
  // バイナリパーサーフォーマット： uptime:0:int:16
  char payload[120];
  sprintf_P(payload, PSTR("+QISENDEX=0,\"%04X\""), uptime_sec);  
  CONSOLE.println(payload);

  // SORACOMに接続
  int mux = 0;
  modem.sendAT(GF("+QIOPEN=1,"), mux, GF(",\"UDP\",\""), ENDPOINT, GF("\","), 23080, GF(",0,0"));
  modem.waitResponse();

  // 接続の応答を待つ
  uint32_t timeout_ms = 15 * 1000; // ライブラリでは150秒だが、長いため15秒とする
  if (modem.waitResponse(timeout_ms, GF(GSM_NL "+QIOPEN:")) != 1) {
    CONSOLE.println(F("failed."));
    delay(3000);
    return;
  }
  
  // 送信
  modem.sendAT(payload);  // send AT command
  // ctx.stop(); // UDP送信の場合不要

  delay(INTERVAL_MS);
}