Hi, Mike
I compile following code in the mbed online compiler, libmDot version is 14, mbed lib version is 119, mbed-rtos lib is 111.
When I download the bin file into mDot 868， the program stop at：“mDot* dot = mDot::getInstance()”.
When using the mDot 915 the programming can pass this line.

Can you help me with this problem, thanks.

#include "mbed.h"
#include "mDot.h"
#include "MTSLog.h"
#include "MTSText.h"
#include <string>
#include <vector>

using namespace mts;

#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))

// AppEUI
uint8_t AppEUI[8] = { 0x70, 0xB3, 0xD5, 0x7E, 0xD0, 0x00, 0x06, 0x56 };
// AppKey
uint8_t AppKey[16] = { 0x7F, 0xA6, 0xF7, 0x50, 0x9F, 0xE5, 0x92, 0x28, 0xD5, 0xF8, 0x79, 0xC3, 0xAD, 0x39, 0x3E, 0xD9 };

#define LORA_SF mDot::DR5
#define LORA_ACK 0
#define LORA_TXPOWER 14

Serial pc(XBEE_DOUT,XBEE_DIN);//tx, rx
 

int main() {
    int32_t ret;
    std::vector<uint8_t> send_data;
    std::vector<uint8_t> recv_data;
    std::vector<uint8_t> nwkId;
    std::vector<uint8_t> nwkKey;

    float temperature = 28.7;
   
    pc.baud(115200);
    pc.printf("TTN OTAA mDot LoRa sensor    \n\r");

    // get a mDot handle
    //
    //dot->setLogLevel(MTSLog::TRACE_LEVEL);

    pc.printf("Checking Config   ");
    // reset to default config so we know what state we're in
    mDot* dot = mDot::getInstance();
    
    pc.printf("Resetting Config    ");

    dot->resetConfig();
    
    uint8_t *it = AppEUI;
    for (uint8_t i = 0; i<8; i++)
        nwkId.push_back((uint8_t) *it++);
    
    it = AppKey;
    for (uint8_t i = 0; i<16; i++)
        nwkKey.push_back((uint8_t) *it++);

/*****************  Config mDot *****************/

    // Set Spreading Factor, higher is lower data rate, smaller packets but longer range
    // Lower is higher data rate, larger packets and shorter range.
    pc.printf("Set SF\n\r");
    if((ret = dot->setTxDataRate( LORA_SF )) != mDot::MDOT_OK) {
        logError("Failed to set SF %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }

    pc.printf("Set TxPower\n\r");
    if((ret = dot->setTxPower( LORA_TXPOWER )) != mDot::MDOT_OK) {
        logError("Failed to set Tx Power %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }

    pc.printf("Set Public mode\n\r");
    if((ret = dot->setPublicNetwork(true)) != mDot::MDOT_OK) {
        logError("failed to set Public Mode %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }

    pc.printf("Set AUTO_OTA Join mode\n\r");
    if((ret = dot->setJoinMode(mDot::AUTO_OTA)) != mDot::MDOT_OK) {
        logError("Failed to set AUTO_OTA Join Mode %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }

    pc.printf("Set Ack\n\r");
    // 1 retries on Ack, 0 to disable
    if((ret = dot->setAck( LORA_ACK)) != mDot::MDOT_OK) {
        logError("Failed to set Ack %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }
    pc.printf("Set Network Id\n\r");
    if ((ret = dot->setNetworkId(nwkId)) != mDot::MDOT_OK) {
        logError("Failed to set Network Id %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }
    pc.printf("Set Network Key\n\r");
    if ((ret = dot->setNetworkKey(nwkKey)) != mDot::MDOT_OK) {
        logError("Failed to set Network Id %d:%s", ret, mDot::getReturnCodeString(ret).c_str());
    }

    pc.printf("Saving Config\n\r");
    // Save config
    if (! dot->saveConfig()) {
        logError("failed to save configuration");
    }
/*****************  print mDot configs *****************/
    pc.printf("Device ID {");
    std::vector<uint8_t> deviceId;
    deviceId = dot->getDeviceId();
    for (std::vector<uint8_t>::iterator it = deviceId.begin() ; it != deviceId.end(); ++it) {
        pc.printf("0x%2.2X",*it );
        pc.printf("%s", it != (deviceId.end() -1 ) ? ", " : " " );
    }
    pc.printf("}\r\n");

    std::vector<uint8_t> netId;
    pc.printf("Network Id/App EUI {");
    netId = dot->getNetworkId();
    for (std::vector<uint8_t>::iterator it = netId.begin() ; it != netId.end(); ++it) {
        pc.printf("0x%2.2X", *it );
        pc.printf("%s", it != (netId.end() -1 ) ? ", " : " " );
    }
    pc.printf("}\r\n");

    std::vector<uint8_t> netKey;
    pc.printf("Network Key/App Key {");
    netKey = dot->getNetworkKey();
    for (std::vector<uint8_t>::iterator it = netKey.begin() ; it != netKey.end(); ++it) {
        pc.printf("0x%2.2X", *it );
        pc.printf("%s", it != (netKey.end() -1 ) ? ", " : " " );
    }
    pc.printf("}\r\n");
/***************** connect *****************/
    pc.printf("Joining Network\n\r");

    while ((ret = dot->joinNetwork()) != mDot::MDOT_OK) {
        logError("failed to join network [%d][%s]", ret, mDot::getReturnCodeString(ret).c_str());
        wait_ms(dot->getNextTxMs() + 1);
    }

    logInfo("Joined Network");
/***************** send data *****************/
    char dataBuf[50];
    while( 1 ) {
        temperature = 30.3;
        sprintf(dataBuf, "{\"t\":%3.1f}", temperature );
        pc.printf("%s\n\r",dataBuf);
        send_data.clear();
        // probably not the most efficent way to do this
        for( int i=0; i< strlen(dataBuf); i++ ) {
            send_data.push_back( dataBuf[i] );
        }

        if ((ret = dot->send(send_data)) != mDot::MDOT_OK) {
             logError("failed to send: [%d][%s]", ret, mDot::getReturnCodeString(ret).c_str());
        } else {
           logInfo("send data: %s", Text::bin2hexString(send_data).c_str());
        }

        // Should  sleep here and wakeup after a set 5 minute interval.
        // in the 868 (EU) frequency band, we need to wait until another channel is available before transmitting again
        uint32_t sleep_time = std::max((uint32_t)10000, (uint32_t)dot->getNextTxMs()) / 1000;
//wait_ms(2000);
        // go to sleep and wake up automatically sleep_time seconds later
        dot->sleep(sleep_time, mDot::RTC_ALARM, false);
    }
    return 0;
}

I tried the same code again, it’s working now. Maybe I did something I have forgotten.

Thanks for running this code for me.

I have send the message {“t”:30.3} to TTN LoRa Server.

Network Key

Saving Config

Device ID {0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0xB8, 0x53 }
Network Id/App EUI {0x70, 0xB3, 0xD5, 0x7E, 0xD0, 0x00, 0x06, 0x56 }
Network Key/App Key {0x7F, 0xA6, 0xF7, 0x50, 0x9F, 0xE5, 0x92, 0x28, 0xD5, 0xF8, 0x79, 0xC3, 0xAD, 0x39, 0x3E, 0xD9 }
Joining Network

{"t":30.3}

{"t":30.3}