SIM800L

// SIM800L on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/sim800l
// SIM800L on an Arduino Uno: module TXD -> D2, module RXD <- D3 (through a 4.7k/5.6k divider)
#include <SoftwareSerial.h>

SoftwareSerial sim800(2, 3); // RX, TX

void sendAT(const char *cmd, unsigned long waitMs) {
  sim800.println(cmd);
  unsigned long start = millis();
  while (millis() - start < waitMs) {
    while (sim800.available()) Serial.write(sim800.read());
  }
  Serial.println();
}

void setup() {
  Serial.begin(115200);
  sim800.begin(9600);
  delay(3000); // give the modem time to boot
  Serial.println(F("SIM800L check"));
  for (int i = 0; i < 3; i++) sendAT("AT", 500); // lets autobauding lock on to 9600
  sendAT("ATI", 500);      // module name and firmware
  sendAT("AT+CSQ", 500);   // signal quality: 0 to 31, 99 = unknown
  sendAT("AT+CCID", 500);  // SIM card ID
  sendAT("AT+CREG?", 500); // ,1 = registered, ,5 = roaming
  Serial.println(F("Type AT commands (set line ending to Both NL & CR)."));
}

void loop() {
  while (Serial.available()) sim800.write(Serial.read());
  while (sim800.available()) Serial.write(sim800.read());
}

// SIM800L on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/sim800l
// SIM800L on an ESP32 DevKit V1: module TXD -> GPIO16, module RXD <- GPIO17 (through a 2.2k/10k divider)
#include <Arduino.h>

const int SIM_RX = 16; // ESP32 receives on GPIO16
const int SIM_TX = 17; // ESP32 transmits on GPIO17

void sendAT(const char *cmd, unsigned long waitMs) {
  Serial2.println(cmd);
  unsigned long start = millis();
  while (millis() - start < waitMs) {
    while (Serial2.available()) Serial.write(Serial2.read());
  }
  Serial.println();
}

void setup() {
  Serial.begin(115200);
  Serial2.begin(9600, SERIAL_8N1, SIM_RX, SIM_TX);
  delay(3000); // give the modem time to boot
  Serial.println("SIM800L check");
  for (int i = 0; i < 3; i++) sendAT("AT", 500); // lets autobauding lock on to 9600
  sendAT("ATI", 500);
  sendAT("AT+CSQ", 500);   // signal quality: 0 to 31, 99 = unknown
  sendAT("AT+CCID", 500);  // SIM card ID
  sendAT("AT+CREG?", 500); // ,1 = registered, ,5 = roaming
  Serial.println("Type AT commands (set line ending to Both NL & CR).");
}

void loop() {
  while (Serial.available()) Serial2.write(Serial.read());
  while (Serial2.available()) Serial.write(Serial2.read());
}

// SIM800L on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/sim800l
// SIM800L on a Raspberry Pi Pico (arduino-pico): module TXD -> GP1, module RXD <- GP0 (through a 2.2k/10k divider)
#include <Arduino.h>

void sendAT(const char *cmd, unsigned long waitMs) {
  Serial1.println(cmd);
  unsigned long start = millis();
  while (millis() - start < waitMs) {
    while (Serial1.available()) Serial.write(Serial1.read());
  }
  Serial.println();
}

void setup() {
  Serial.begin(115200);
  Serial1.setTX(0);
  Serial1.setRX(1);
  Serial1.begin(9600);
  delay(3000); // give the modem time to boot
  Serial.println("SIM800L check");
  for (int i = 0; i < 3; i++) sendAT("AT", 500); // lets autobauding lock on to 9600
  sendAT("ATI", 500);
  sendAT("AT+CSQ", 500);   // signal quality: 0 to 31, 99 = unknown
  sendAT("AT+CCID", 500);  // SIM card ID
  sendAT("AT+CREG?", 500); // ,1 = registered, ,5 = roaming
  Serial.println("Type AT commands (set line ending to Both NL & CR).");
}

void loop() {
  while (Serial.available()) Serial1.write(Serial.read());
  while (Serial1.available()) Serial.write(Serial1.read());
}