Last character of SMS missing, Adafruit_Fona with SIM7670G. No problem with SIM7600NA.

[Aaron2]

This seems library related, but the cause isn't apparent to me.
This same test code(and Arduino Nano) is fine with a SimCom A7670G module, but not with a SimCom SIM7670G module.

When receiving any length test SMS message, the last character disappears, regardless of message length, Like send: "Test edaboard" received: "Test edaboar".
This SIM7670G receives the full SMS message when tested with direct USB connection (Putty) and AT Command Tester.

This is the test code used with Arduino Nano:

#include "Adafruit_FONA.h"
#define FONA_RST 4

char replybuffer[255];  // this is a large buffer for replies

//#if (defined(__AVR__) || defined(ESP8266)) && !defined(__AVR_ATmega2560__)
// For UNO and others without hardware serial,
// we default to using software serial. If you want to use hardware serial
// (because softserial isnt supported) comment out the following three lines
// and uncomment the HardwareSerial line
#include <SoftwareSerial.h>

#define FONA_RX 4  //2
#define FONA_TX 3

SoftwareSerial fonaSS = SoftwareSerial(FONA_TX, FONA_RX);
SoftwareSerial *fonaSerial = &fonaSS;

//#else
// On Leonardo/M0/etc, others with hardware serial, use hardware serial!
//HardwareSerial *fonaSerial = &Serial1;
//#endif

// Use this for FONA 800 and 808s
    //Adafruit_FONA fona = Adafruit_FONA(FONA_RST);
// Use this one for FONA 3G
    Adafruit_FONA_3G fona = Adafruit_FONA_3G(FONA_RST);

uint8_t readline(char *buff, uint8_t maxbuff, uint16_t timeout = 0);

void setup() {
  while (!Serial);

  Serial.begin(9600);
  Serial.println(F("FONA SMS caller ID test"));
  Serial.println(F("Initializing....(May take 3 seconds)"));

  // make it slow so its easy to read!
  fonaSerial->begin(9600);
  if (! fona.begin(*fonaSerial)) {
    Serial.println(F("Couldn't find FONA"));
    while(1);
  }
  Serial.println(F("FONA is OK"));

  // Print SIM card IMEI number.
  char imei[16] = {0}; // MUST use a 16 character buffer for IMEI!
  uint8_t imeiLen = fona.getIMEI(imei);
  if (imeiLen > 0) {
    Serial.print("SIM card IMEI: "); Serial.println(imei);
  }

  fonaSerial->print("AT+CNMI=2,1\r\n");  //set up the FONA to send a +CMTI notification when an SMS is received
  Serial.println("FONA Ready");
}

char fonaNotificationBuffer[64];          //for notifications from the FONA
char smsBuffer[250];

void loop() {
 
  char* bufPtr = fonaNotificationBuffer;    //handy buffer pointer
 
  if (fona.available())      //any data available from the FONA?
  {
    int slot = 0;            //this will be the slot number of the SMS
    int charCount = 0;
    //Read the notification into fonaInBuffer
    do  {
      *bufPtr = fona.read();
      Serial.write(*bufPtr);
      delay(1);
    } while ((*bufPtr++ != '\n') && (fona.available()) && (++charCount < (sizeof(fonaNotificationBuffer)-1)));
    
    //Add a terminal NULL to the notification string
    *bufPtr = 0;

    //Scan the notification string for an SMS received notification.
    //  If it's an SMS message, we'll get the slot number in 'slot'
    if (1 == sscanf(fonaNotificationBuffer, "+CMTI: " FONA_PREF_SMS_STORAGE ",%d", &slot)) {
      Serial.print("slot: "); Serial.println(slot);
      
      char callerIDbuffer[32];  //we'll store the SMS sender number in here
      
      // Retrieve SMS sender address/phone number.
      if (! fona.getSMSSender(slot, callerIDbuffer, 31)) {
        Serial.println("Didn't find SMS message in slot!");
      }
      Serial.print(F("FROM: ")); Serial.println(callerIDbuffer);

        // Retrieve SMS value.
        uint16_t smslen;
        if (fona.readSMS(slot, smsBuffer, 250, &smslen)) { // pass in buffer and max len!
          Serial.println(smsBuffer);
        }
    }
  }
}

Adafruit_Fona library here.

Has anyone else experienced this?

 

[aliarifat794]

You can increase the buffer size in your code and see if the problem disappear.

 

[Aaron2]

Is it really a buffer size issue?
This happens if the text message is 7 characters or 27, the last digit or letter is not displaying in the serial monitor, and the code is not executing functions based on the received message. Like LED13 ON. Displayed as LED13 O. Plus, the missing character is occurring only with the SIM7670G, not the SIM7600NA or A7670G based modules. Same code and library.