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SIGABRT error when returning from C++ code from java module in android

Still new to android and java but learning more each day :)
This question refers to
Ok, the error refers to
expression failed to parse:
error: <user expression 27>:1:1: 'bl' has unknown type; cast it to its declared type to use it
bl
^~
and
expression failed to parse:
error: <user expression 28>:1:1: 'uxtb' has unknown type; cast it to its declared type to use it
uxtb.w
^~~~
I call (will want a short ) result = getCheckSum(A, B); from my java code.
The method in my C++ code is
//---------------------------------------------------------------------------
unsigned short ekmCheckCRC16(const unsigned char *dat, unsigned short len)
{
unsigned short crc = 0xffff;
while (len--)
{
crc = (crc >> 8 ) ^ ekmCrcLut[(crc ^ *dat++) & 0xff];
}
crc = (crc << 8 ) | (crc >> 8);
crc &= 0x7f7f;
return crc;
}
//---------------------------------------------------------------------------
// Implementation of the native method getCheckSum()
extern "C"
JNIEXPORT unsigned short JNICALL
Java_com_(...)_getCheckSum(JNIEnv *env, jobject thiz, jstring a) {
const char * aCStr = env->GetStringUTFChars(a, NULL);
if(NULL == aCStr)
return NULL;
unsigned short crc = ekmCheckCRC16(reinterpret_cast<const unsigned char *>(aCStr), strlen(aCStr));
return crc;
}
This code is experimental showing the actual code I want to run ekmCheckCRC16( ... ), its purpose is to learn how to return a value back to the java module.
The error message seems to be clear 'unknown' type cast, so question is, how should I be returning the value of aCStr?
Thanks in advance.

Solved my problem, was simple error of not changing one important detail before executing call i was looking for a return type of short but had String in native declaration.
I had
private native String getCheckSum(String a);
it should have been
`private native short getCheckSum(String a);`
My call was / is
short result = getCheckSum(A);
Worked fine after correcting my mistake.
for those interested my c++ code
#include <jni.h> // JNI header provided by JDK
#include "ekmCheckSum.h"
#include <iostream> // C++ standard IO header
using namespace std;
//---------------------------------------------------------------------------
void ekmCheckSum() {
}
static const unsigned short ekmCrcLut[256] = {
0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241,
0xc601, 0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440,
0xcc01, 0x0cc0, 0x0d80, 0xcd41, 0x0f00, 0xcfc1, 0xce81, 0x0e40,
0x0a00, 0xcac1, 0xcb81, 0x0b40, 0xc901, 0x09c0, 0x0880, 0xc841,
0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40,
0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41,
0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641,
0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 0x1040,
0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1, 0xf281, 0x3240,
0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441,
0x3c00, 0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41,
0xfa01, 0x3ac0, 0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840,
0x2800, 0xe8c1, 0xe981, 0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41,
0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1, 0xec81, 0x2c40,
0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640,
0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 0x2080, 0xe041,
0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240,
0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441,
0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41,
0xaa01, 0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840,
0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41,
0xbe01, 0x7ec0, 0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40,
0xb401, 0x74c0, 0x7580, 0xb541, 0x7700, 0xb7c1, 0xb681, 0x7640,
0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0, 0x7080, 0xb041,
0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 0x5280, 0x9241,
0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440,
0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40,
0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841,
0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40,
0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41,
0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641,
0x8201, 0x42c0, 0x4380, 0x8341, 0x4100, 0x81c1, 0x8081, 0x4040
};
//---------------------------------------------------------------------------
unsigned short ekmCheckCRC16(const unsigned char *dat, unsigned short len)
{
unsigned short crc = 0xffff;
while (len--)
{
crc = (crc >> 8 ) ^ ekmCrcLut[(crc ^ *dat++) & 0xff];
}
crc = (crc << 8 ) | (crc >> 8);
crc &= 0x7f7f;
return crc;
}
//---------------------------------------------------------------------------
// Implementation of the native method getCheckSum()
extern "C"
JNIEXPORT unsigned short JNICALL
Java_com_[project name]_ekmV4Fields_getCheckSum(JNIEnv *env, jobject thiz, jstring a) {
const char * aCStr = env->GetStringUTFChars(a, NULL);
if(NULL == aCStr)
return NULL;
unsigned short crc = ekmCheckCRC16(reinterpret_cast<const unsigned char *>(aCStr), strlen(aCStr));
return crc;
}
my .h file contains
#ifndef PROJECT_NAME_EKMCHECKSUM_H
#define PROJECT_NAME_EKMCHECKSUM_H
class ekmCheckSum
{
private:
public:
ekmCheckSum();
unsigned short ekmCheckCRC16(const unsigned char *dat, unsigned short len);
};
#endif //PROJECT_NAME_EKMCHECKSUM_H
my java file includes
static {System.loadLibrary("ekmCheckSum");}
private native short getCheckSum(String a);
public void SetEkmFieldValueStrings(String A, String B)
{
/* if length of A is less than 250 chars, read is no good, discard
* NOTE: both Strings A and B will need to be validated for checksum
* TODO check A & B if checksum is correct
* */
boolean _aOk = false, _bOk=false;
short result = getCheckSum(A);
...
...

How to LocalDateTime but use server time or internet time? [duplicate]

I would like to get the GMT [ Greenwich Mean Time ], and also I don't want to rely on my system date time for that. Basically, I want to use time sync server like in.pool.ntp.org [ India ] for GMT calculation, or may be I am going in wrong direction!
How to do this in java ?
Is there any java library to get time from Time server?

sp0d is not quite right:
timeInfo.getReturnTime(); // Returns time at which time message packet was received by local machine
So it just returns current system time, not the received one. See TimeInfo man page.
You should use
timeInfo.getMessage().getTransmitTimeStamp().getTime();
instead.
So the code block will be:
String TIME_SERVER = "time-a.nist.gov";
NTPUDPClient timeClient = new NTPUDPClient();
InetAddress inetAddress = InetAddress.getByName(TIME_SERVER);
TimeInfo timeInfo = timeClient.getTime(inetAddress);
long returnTime = timeInfo.getMessage().getTransmitTimeStamp().getTime();
Date time = new Date(returnTime);

Here is a code i found somewhere else.. and i am using it. Uses apache commons library.
List of time servers: NIST Internet Time Service
import java.net.InetAddress;
import java.util.Date;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;
public class TimeLookup {
public static void main() throws Exception {
String TIME_SERVER = "time-a.nist.gov";
NTPUDPClient timeClient = new NTPUDPClient();
InetAddress inetAddress = InetAddress.getByName(TIME_SERVER);
TimeInfo timeInfo = timeClient.getTime(inetAddress);
long returnTime = timeInfo.getReturnTime();
Date time = new Date(returnTime);
System.out.println("Time from " + TIME_SERVER + ": " + time);
}
}
Returns the output
Time from time-d.nist.gov: Sun Nov 25 06:04:34 IST 2012

I know this is an old question but I notice that all the answers are not correct or are complicated.
A nice and simple way to implement it is using Apache Commons Net library. This library will provide a NTPUDPClient class to manage connectionless NTP requests. This class will return a TimeInfo instance. This object should run the compute method to calculate the offset between your system's time and the NTP server's time. Lets try to implement it here
Add the Apache Commons Net library to your project.
<dependency>
<groupId>commons-net</groupId>
<artifactId>commons-net</artifactId>
<version>3.6</version>
</dependency>
Create a new instance of the NTPUDPClient class.
Setup the default timeout
Get the InetAddress of the NTP Server.
Call the NTPUDPClient.getTime() method to retrieve a TimeInfo instance with the time information from the specified server.
Call the computeDetails() method to compute and validate details of the NTP message packet.
Finally, get a NTP timestamp object based on a Java time by using this code TimeStamp.getNtpTime(currentTime + offset).getTime().
Here we have a basic implementation:
import java.net.InetAddress;
import java.util.Date;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;
public class NTPClient {
private static final String SERVER_NAME = "pool.ntp.org";
private volatile TimeInfo timeInfo;
private volatile Long offset;
public static void main() throws Exception {
NTPUDPClient client = new NTPUDPClient();
// We want to timeout if a response takes longer than 10 seconds
client.setDefaultTimeout(10_000);
InetAddress inetAddress = InetAddress.getByName(SERVER_NAME);
TimeInfo timeInfo = client.getTime(inetAddress);
timeInfo.computeDetails();
if (timeInfo.getOffset() != null) {
this.timeInfo = timeInfo;
this.offset = timeInfo.getOffset();
}
// This system NTP time
TimeStamp systemNtpTime = TimeStamp.getCurrentTime();
System.out.println("System time:\t" + systemNtpTime + " " + systemNtpTime.toDateString());
// Calculate the remote server NTP time
long currentTime = System.currentTimeMillis();
TimeStamp atomicNtpTime = TimeStamp.getNtpTime(currentTime + offset).getTime()
System.out.println("Atomic time:\t" + atomicNtpTime + " " + atomicNtpTime.toDateString());
}
public boolean isComputed()
{
return timeInfo != null && offset != null;
}
}
You will get something like that:
System time: dfaa2c15.2083126e Thu, Nov 29 2018 18:12:53.127
Atomic time: dfaa2c15.210624dd Thu, Nov 29 2018 18:12:53.129

This link demonstrates a java class called NtpMessage.java that you can paste into your program which will fetch the current time from an NTP server.
At the following link, Find the "Attachment" section near the bottom and download NtpMessage.java and SntpClient.java and paste it into your java application. It will do all the work and fetch you the time.
http://support.ntp.org/bin/view/Support/JavaSntpClient
Copy and paste of the code if it goes down:
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
* This class represents a NTP message, as specified in RFC 2030. The message
* format is compatible with all versions of NTP and SNTP.
*
* This class does not support the optional authentication protocol, and
* ignores the key ID and message digest fields.
*
* For convenience, this class exposes message values as native Java types, not
* the NTP-specified data formats. For example, timestamps are
* stored as doubles (as opposed to the NTP unsigned 64-bit fixed point
* format).
*
* However, the contructor NtpMessage(byte[]) and the method toByteArray()
* allow the import and export of the raw NTP message format.
*
*
* Usage example
*
* // Send message
* DatagramSocket socket = new DatagramSocket();
* InetAddress address = InetAddress.getByName("ntp.cais.rnp.br");
* byte[] buf = new NtpMessage().toByteArray();
* DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 123);
* socket.send(packet);
*
* // Get response
* socket.receive(packet);
* System.out.println(msg.toString());
*
*
* This code is copyright (c) Adam Buckley 2004
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version. A HTML version of the GNU General Public License can be
* seen at http://www.gnu.org/licenses/gpl.html
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
*
* Comments for member variables are taken from RFC2030 by David Mills,
* University of Delaware.
*
* Number format conversion code in NtpMessage(byte[] array) and toByteArray()
* inspired by http://www.pps.jussieu.fr/~jch/enseignement/reseaux/
* NTPMessage.java which is copyright (c) 2003 by Juliusz Chroboczek
*
* #author Adam Buckley
*/
public class NtpMessage
{
/**
* This is a two-bit code warning of an impending leap second to be
* inserted/deleted in the last minute of the current day. It's values
* may be as follows:
*
* Value Meaning
* ----- -------
* 0 no warning
* 1 last minute has 61 seconds
* 2 last minute has 59 seconds)
* 3 alarm condition (clock not synchronized)
*/
public byte leapIndicator = 0;
/**
* This value indicates the NTP/SNTP version number. The version number
* is 3 for Version 3 (IPv4 only) and 4 for Version 4 (IPv4, IPv6 and OSI).
* If necessary to distinguish between IPv4, IPv6 and OSI, the
* encapsulating context must be inspected.
*/
public byte version = 3;
/**
* This value indicates the mode, with values defined as follows:
*
* Mode Meaning
* ---- -------
* 0 reserved
* 1 symmetric active
* 2 symmetric passive
* 3 client
* 4 server
* 5 broadcast
* 6 reserved for NTP control message
* 7 reserved for private use
*
* In unicast and anycast modes, the client sets this field to 3 (client)
* in the request and the server sets it to 4 (server) in the reply. In
* multicast mode, the server sets this field to 5 (broadcast).
*/
public byte mode = 0;
/**
* This value indicates the stratum level of the local clock, with values
* defined as follows:
*
* Stratum Meaning
* ----------------------------------------------
* 0 unspecified or unavailable
* 1 primary reference (e.g., radio clock)
* 2-15 secondary reference (via NTP or SNTP)
* 16-255 reserved
*/
public short stratum = 0;
/**
* This value indicates the maximum interval between successive messages,
* in seconds to the nearest power of two. The values that can appear in
* this field presently range from 4 (16 s) to 14 (16284 s); however, most
* applications use only the sub-range 6 (64 s) to 10 (1024 s).
*/
public byte pollInterval = 0;
/**
* This value indicates the precision of the local clock, in seconds to
* the nearest power of two. The values that normally appear in this field
* range from -6 for mains-frequency clocks to -20 for microsecond clocks
* found in some workstations.
*/
public byte precision = 0;
/**
* This value indicates the total roundtrip delay to the primary reference
* source, in seconds. Note that this variable can take on both positive
* and negative values, depending on the relative time and frequency
* offsets. The values that normally appear in this field range from
* negative values of a few milliseconds to positive values of several
* hundred milliseconds.
*/
public double rootDelay = 0;
/**
* This value indicates the nominal error relative to the primary reference
* source, in seconds. The values that normally appear in this field
* range from 0 to several hundred milliseconds.
*/
public double rootDispersion = 0;
/**
* This is a 4-byte array identifying the particular reference source.
* In the case of NTP Version 3 or Version 4 stratum-0 (unspecified) or
* stratum-1 (primary) servers, this is a four-character ASCII string, left
* justified and zero padded to 32 bits. In NTP Version 3 secondary
* servers, this is the 32-bit IPv4 address of the reference source. In NTP
* Version 4 secondary servers, this is the low order 32 bits of the latest
* transmit timestamp of the reference source. NTP primary (stratum 1)
* servers should set this field to a code identifying the external
* reference source according to the following list. If the external
* reference is one of those listed, the associated code should be used.
* Codes for sources not listed can be contrived as appropriate.
*
* Code External Reference Source
* ---- -------------------------
* LOCL uncalibrated local clock used as a primary reference for
* a subnet without external means of synchronization
* PPS atomic clock or other pulse-per-second source
* individually calibrated to national standards
* ACTS NIST dialup modem service
* USNO USNO modem service
* PTB PTB (Germany) modem service
* TDF Allouis (France) Radio 164 kHz
* DCF Mainflingen (Germany) Radio 77.5 kHz
* MSF Rugby (UK) Radio 60 kHz
* WWV Ft. Collins (US) Radio 2.5, 5, 10, 15, 20 MHz
* WWVB Boulder (US) Radio 60 kHz
* WWVH Kaui Hawaii (US) Radio 2.5, 5, 10, 15 MHz
* CHU Ottawa (Canada) Radio 3330, 7335, 14670 kHz
* LORC LORAN-C radionavigation system
* OMEG OMEGA radionavigation system
* GPS Global Positioning Service
* GOES Geostationary Orbit Environment Satellite
*/
public byte[] referenceIdentifier = {0, 0, 0, 0};
/**
* This is the time at which the local clock was last set or corrected, in
* seconds since 00:00 1-Jan-1900.
*/
public double referenceTimestamp = 0;
/**
* This is the time at which the request departed the client for the
* server, in seconds since 00:00 1-Jan-1900.
*/
public double originateTimestamp = 0;
/**
* This is the time at which the request arrived at the server, in seconds
* since 00:00 1-Jan-1900.
*/
public double receiveTimestamp = 0;
/**
* This is the time at which the reply departed the server for the client,
* in seconds since 00:00 1-Jan-1900.
*/
public double transmitTimestamp = 0;
/**
* Constructs a new NtpMessage from an array of bytes.
*/
public NtpMessage(byte[] array)
{
// See the packet format diagram in RFC 2030 for details
leapIndicator = (byte) ((array[0] >> 6) & 0x3);
version = (byte) ((array[0] >> 3) & 0x7);
mode = (byte) (array[0] & 0x7);
stratum = unsignedByteToShort(array[1]);
pollInterval = array[2];
precision = array[3];
rootDelay = (array[4] * 256.0) +
unsignedByteToShort(array[5]) +
(unsignedByteToShort(array[6]) / 256.0) +
(unsignedByteToShort(array[7]) / 65536.0);
rootDispersion = (unsignedByteToShort(array[8]) * 256.0) +
unsignedByteToShort(array[9]) +
(unsignedByteToShort(array[10]) / 256.0) +
(unsignedByteToShort(array[11]) / 65536.0);
referenceIdentifier[0] = array[12];
referenceIdentifier[1] = array[13];
referenceIdentifier[2] = array[14];
referenceIdentifier[3] = array[15];
referenceTimestamp = decodeTimestamp(array, 16);
originateTimestamp = decodeTimestamp(array, 24);
receiveTimestamp = decodeTimestamp(array, 32);
transmitTimestamp = decodeTimestamp(array, 40);
}
/**
* Constructs a new NtpMessage in client -> server mode, and sets the
* transmit timestamp to the current time.
*/
public NtpMessage()
{
// Note that all the other member variables are already set with
// appropriate default values.
this.mode = 3;
this.transmitTimestamp = (System.currentTimeMillis()/1000.0) + 2208988800.0;
}
/**
* This method constructs the data bytes of a raw NTP packet.
*/
public byte[] toByteArray()
{
// All bytes are automatically set to 0
byte[] p = new byte[48];
p[0] = (byte) (leapIndicator << 6 | version << 3 | mode);
p[1] = (byte) stratum;
p[2] = (byte) pollInterval;
p[3] = (byte) precision;
// root delay is a signed 16.16-bit FP, in Java an int is 32-bits
int l = (int) (rootDelay * 65536.0);
p[4] = (byte) ((l >> 24) & 0xFF);
p[5] = (byte) ((l >> 16) & 0xFF);
p[6] = (byte) ((l >> 8) & 0xFF);
p[7] = (byte) (l & 0xFF);
// root dispersion is an unsigned 16.16-bit FP, in Java there are no
// unsigned primitive types, so we use a long which is 64-bits
long ul = (long) (rootDispersion * 65536.0);
p[8] = (byte) ((ul >> 24) & 0xFF);
p[9] = (byte) ((ul >> 16) & 0xFF);
p[10] = (byte) ((ul >> 8) & 0xFF);
p[11] = (byte) (ul & 0xFF);
p[12] = referenceIdentifier[0];
p[13] = referenceIdentifier[1];
p[14] = referenceIdentifier[2];
p[15] = referenceIdentifier[3];
encodeTimestamp(p, 16, referenceTimestamp);
encodeTimestamp(p, 24, originateTimestamp);
encodeTimestamp(p, 32, receiveTimestamp);
encodeTimestamp(p, 40, transmitTimestamp);
return p;
}
/**
* Returns a string representation of a NtpMessage
*/
public String toString()
{
String precisionStr =
new DecimalFormat("0.#E0").format(Math.pow(2, precision));
return "Leap indicator: " + leapIndicator + "\n" +
"Version: " + version + "\n" +
"Mode: " + mode + "\n" +
"Stratum: " + stratum + "\n" +
"Poll: " + pollInterval + "\n" +
"Precision: " + precision + " (" + precisionStr + " seconds)\n" +
"Root delay: " + new DecimalFormat("0.00").format(rootDelay*1000) + " ms\n" +
"Root dispersion: " + new DecimalFormat("0.00").format(rootDispersion*1000) + " ms\n" +
"Reference identifier: " + referenceIdentifierToString(referenceIdentifier, stratum, version) + "\n" +
"Reference timestamp: " + timestampToString(referenceTimestamp) + "\n" +
"Originate timestamp: " + timestampToString(originateTimestamp) + "\n" +
"Receive timestamp: " + timestampToString(receiveTimestamp) + "\n" +
"Transmit timestamp: " + timestampToString(transmitTimestamp);
}
/**
* Converts an unsigned byte to a short. By default, Java assumes that
* a byte is signed.
*/
public static short unsignedByteToShort(byte b)
{
if((b & 0x80)==0x80) return (short) (128 + (b & 0x7f));
else return (short) b;
}
/**
* Will read 8 bytes of a message beginning at <code>pointer</code>
* and return it as a double, according to the NTP 64-bit timestamp
* format.
*/
public static double decodeTimestamp(byte[] array, int pointer)
{
double r = 0.0;
for(int i=0; i<8; i++)
{
r += unsignedByteToShort(array[pointer+i]) * Math.pow(2, (3-i)*8);
}
return r;
}
/**
* Encodes a timestamp in the specified position in the message
*/
public static void encodeTimestamp(byte[] array, int pointer, double timestamp)
{
// Converts a double into a 64-bit fixed point
for(int i=0; i<8; i++)
{
// 2^24, 2^16, 2^8, .. 2^-32
double base = Math.pow(2, (3-i)*8);
// Capture byte value
array[pointer+i] = (byte) (timestamp / base);
// Subtract captured value from remaining total
timestamp = timestamp - (double) (unsignedByteToShort(array[pointer+i]) * base);
}
// From RFC 2030: It is advisable to fill the non-significant
// low order bits of the timestamp with a random, unbiased
// bitstring, both to avoid systematic roundoff errors and as
// a means of loop detection and replay detection.
array[7] = (byte) (Math.random()*255.0);
}
/**
* Returns a timestamp (number of seconds since 00:00 1-Jan-1900) as a
* formatted date/time string.
*/
public static String timestampToString(double timestamp)
{
if(timestamp==0) return "0";
// timestamp is relative to 1900, utc is used by Java and is relative
// to 1970
double utc = timestamp - (2208988800.0);
// milliseconds
long ms = (long) (utc * 1000.0);
// date/time
String date = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss").format(new Date(ms));
// fraction
double fraction = timestamp - ((long) timestamp);
String fractionSting = new DecimalFormat(".000000").format(fraction);
return date + fractionSting;
}
/**
* Returns a string representation of a reference identifier according
* to the rules set out in RFC 2030.
*/
public static String referenceIdentifierToString(byte[] ref, short stratum, byte version)
{
// From the RFC 2030:
// In the case of NTP Version 3 or Version 4 stratum-0 (unspecified)
// or stratum-1 (primary) servers, this is a four-character ASCII
// string, left justified and zero padded to 32 bits.
if(stratum==0 || stratum==1)
{
return new String(ref);
}
// In NTP Version 3 secondary servers, this is the 32-bit IPv4
// address of the reference source.
else if(version==3)
{
return unsignedByteToShort(ref[0]) + "." +
unsignedByteToShort(ref[1]) + "." +
unsignedByteToShort(ref[2]) + "." +
unsignedByteToShort(ref[3]);
}
// In NTP Version 4 secondary servers, this is the low order 32 bits
// of the latest transmit timestamp of the reference source.
else if(version==4)
{
return "" + ((unsignedByteToShort(ref[0]) / 256.0) +
(unsignedByteToShort(ref[1]) / 65536.0) +
(unsignedByteToShort(ref[2]) / 16777216.0) +
(unsignedByteToShort(ref[3]) / 4294967296.0));
}
return "";
}
}

The server time-a.nist.gov does not list the time port; you have to use correct server ntp.xs4all.nl for getting date and time from internet:
String TIME_SERVER = "ntp.xs4all.nl";
//... some other code

Translating a CRC algorithm from C to Java

I have the below code which I am trying to convert to Java.
WORD ComputeCRC16(BYTE *data, DWORD data_length)
{
BYTE *ptr;
BYTEWORD retval;
/* Initialize the CRC */
retval.w = 0xFFFF;
/* Iterate through the data */
for (ptr=data; ptr<data+data_length; ptr++)
{
// retval.w = IterateCRC16(ptr, retval);
retval.w = retval.b.hi ^ (ccittrev_tbl[retval.b.lo ^ *ptr]);
}
/* Finalize the CRC */
retval.w = ~retval.w;
/* Done. */
return retval.w;
}
What does the below line mean?
retval.w = retval.b.hi ^ (ccittrev_tbl[retval.b.lo ^ *ptr]);
retval should be an int if i convert to Java right? If then how can it have a memeber called "w" ? Please advice how I can convert the above line to Java?
I'm editing the question to post this part I had missed.
typedef union
{
WORD w;
struct
{
BYTE lo,
hi;
} b;
} BYTEWORD;
Edited after suggestions :
static int calculate_crc(byte[] data) {
int retval_w = 0x0000;
int ccittrev_tbl[] = {
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
};
for (byte b : data) {
retval_w = ((retval_w>>8)&0xff) ^ (ccittrev_tbl[(retval_w&0xff) ^ b]);
}
}

According to code I guess the BYTEWORD is a union of unsigned short and structure of two bytes, so the author could easily access high and low byte of this short, i.e.:
typedef union BYTEWORD
{
short w;
struct {
char lo, hi;
} b;
} BYTEWORD;
As java doesn't support unions (and as mentioned in discussion, there are endian flaws with the above), you will have to use >>, | and & operators to access to high and low 8 bits of the short:
short retval_w = -1;
...
retval_w = ((retval_w>>8)&0xff) ^ (ccittrev_tbl[(retval_w&0xff) ^ (data[i]&0xff)]);

The ^ is a binary operator which means Exclusive OR (XOR).

Arduino MPU6050 Sensor Not Working with Code from Arduino's Website

I keep getting the following in the serial monitor over and over:
AcX = -1 | AcY = -1 | AcZ = -1 | Tmp = 36.53 | GyX = -1 | GyY = -1 | GyZ = -1
I am using the following code that I got off http://playground.arduino.cc/Main/MPU-6050#sketch:
// MPU-6050 Short Example Sketch
// By Arduino User JohnChi
// August 17, 2014
// Public Domain
#include<Wire.h>
const int MPU=0x68; // I2C address of the MPU-6050
int16_t AcX,AcY,AcZ,Tmp,GyX,GyY,GyZ;
void setup(){
Wire.begin();
Wire.beginTransmission(MPU);
Wire.write(0x6B); // PWR_MGMT_1 register
Wire.write(0); // set to zero (wakes up the MPU-6050)
Wire.endTransmission(true);
Serial.begin(9600);
}
void loop(){
Wire.beginTransmission(MPU);
Wire.write(0x3B); // starting with register 0x3B (ACCEL_XOUT_H)
Wire.endTransmission(false);
Wire.requestFrom(MPU,14,true); // request a total of 14 registers
AcX=Wire.read()<<8|Wire.read(); // 0x3B (ACCEL_XOUT_H) & 0x3C (ACCEL_XOUT_L)
AcY=Wire.read()<<8|Wire.read(); // 0x3D (ACCEL_YOUT_H) & 0x3E (ACCEL_YOUT_L)
AcZ=Wire.read()<<8|Wire.read(); // 0x3F (ACCEL_ZOUT_H) & 0x40 (ACCEL_ZOUT_L)
Tmp=Wire.read()<<8|Wire.read(); // 0x41 (TEMP_OUT_H) & 0x42 (TEMP_OUT_L)
GyX=Wire.read()<<8|Wire.read(); // 0x43 (GYRO_XOUT_H) & 0x44 (GYRO_XOUT_L)
GyY=Wire.read()<<8|Wire.read(); // 0x45 (GYRO_YOUT_H) & 0x46 (GYRO_YOUT_L)
GyZ=Wire.read()<<8|Wire.read(); // 0x47 (GYRO_ZOUT_H) & 0x48 (GYRO_ZOUT_L)
Serial.print("AcX = "); Serial.print(AcX);
Serial.print(" | AcY = "); Serial.print(AcY);
Serial.print(" | AcZ = "); Serial.print(AcZ);
Serial.print(" | Tmp = "); Serial.print(Tmp/340.00+36.53); //equation for temperature in degrees C from datasheet
Serial.print(" | GyX = "); Serial.print(GyX);
Serial.print(" | GyY = "); Serial.print(GyY);
Serial.print(" | GyZ = "); Serial.println(GyZ);
delay(333);
}
This is the wiring I am using: http://jamesmpoe.com/roboticswiki/images/4/45/MPU6050-Arduino-Uno-Connections.jpg
I do not know what is wrong.
Thank you for your help.

First of all, I'd set the clock to the X gyroscope oscillator instead of the internal oscillator (as it is suggested on the MPU6050 datasheet), hence
Wire.beginTransmission(MPU);
Wire.write(0x6B); // PWR_MGMT_1 register
Wire.write(1); // set to one to turn on the Xgyro oscillator
Wire.endTransmission(true);
In my project, however, I wrote a lot more initializations... I suggest you to
Write some functions to write/read bit(s), byte(s) and word(s) on the I2C interface, because you'll need them
Write functions to get and set the important parts of the registers in the MPU6050
Write more complex functions.
Examples:
// I2C interface
bool i2c_writeBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t* data)
{
Wire.beginTransmission(devAddr);
Wire.write((uint8_t) regAddr); // send address
for (uint8_t i = 0; i < length; i++)
{
Wire.write((uint8_t) data[i]);
}
return (Wire.endTransmission() == 0);
}
// Simple function
int16_t mpu6050_getAccelerationX() {
i2c_readBytes(MPU6050_ADDRESS, MPU6050_RA_ACCEL_XOUT_H, 2, rwBuffer);
return (((int16_t)rwBuffer[0]) << 8) | rwBuffer[1];
}
// Complex function
void mpu6050_initialize()
{
mpu6050_reset();
delay(100);
mpu6050_setClockSource(MPU6050_CLOCK_PLL_XGYRO);
mpu6050_setSleepEnabled(false);
mpu6050_setWakeCycleEnabled(false);
mpu6050_switchSPIEnabled(false);
mpu6050_setI2CMasterModeEnabled(false);
mpu6050_setFIFOEnabled(false);
delay(100);
mpu6050_setRate(7); // 1kHz scan freq
mpu6050_setDLPFMode(MPU6050_DLPF_BW_256);
mpu6050_setFullScaleGyroRange(MPU6050_GYRO_FS_250);
mpu6050_setFullScaleAccelRange(MPU6050_ACCEL_FS_2);
mpu6050_setInterruptMode(MPU6050_INTMODE_ACTIVEHIGH);
mpu6050_setInterruptDrive(MPU6050_INTDRV_PUSHPULL);
mpu6050_setInterruptLatch(MPU6050_INTLATCH_WAITCLEAR);
mpu6050_setInterruptLatchClear(MPU6050_INTCLEAR_ANYREAD);
mpu6050_setFSyncInterruptEnabled(0);
mpu6050_setI2CBypassEnabled(0);
mpu6050_setClockOutputEnabled(0);
mpu6050_setIntEnabled(MPU6050_INTERRUPT_MASK_DATA_RDY_BIT); // Interrupt when data ready
}
A useful resource is the MPU6050 registers map (you can find it here).

It was a soldering error.
It works perfectly with the code above.

CCITT (Convert C code to JAVA)

I am trying to validate checksums from a device and they give me the below C code for checksum validation, however I cannot convert this code to java and get it to produce the same checksum as the messages. Note this is the entire source code given in document and i have tried several of the example codes online and none of them work for me. Thanks.
const unsigned short NET_CRC_TABLE[256] =
{ 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7, 0x8108, 0x9129,
0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 0x1231, 0x0210, 0x3273, 0x2252, 0x52B5,
0x4294, 0x72F7, 0x62D6, 0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485, 0xA56A, 0xB54B, 0x8528,
0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D, 0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6,
0x5695, 0x46B4, 0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC, 0x48C4,
0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823, 0xC9CC, 0xD9ED, 0xE98E, 0xF9AF,
0x8948, 0x9969, 0xA90A, 0xB92B, 0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33,
0x2A12, 0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A, 0x6CA6, 0x7C87,
0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A,
0xBD0B, 0x8D68, 0x9D49, 0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78, 0x9188, 0x81A9, 0xB1CA,
0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F, 0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025,
0x7046, 0x6067, 0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E, 0x02B1,
0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256, 0xB5EA, 0xA5CB, 0x95A8, 0x8589,
0xF56E, 0xE54F, 0xD52C, 0xC50D, 0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424,
0x4405, 0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C, 0x26D3, 0x36F2,
0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634, 0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8,
0x89E9, 0xB98A, 0xA9AB, 0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A, 0x4A75, 0x5A54, 0x6A37,
0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92, 0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B,
0x9DE8, 0x8DC9, 0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1, 0xEF1F,
0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8, 0x6E17, 0x7E36, 0x4E55, 0x5E74,
0x2E93, 0x3EB2, 0x0ED1, 0x1EF0 };
unsigned short NET_CRC_Calc(unsigned char * pData, unsigned short Count)
{ /* calculate serial CRC (<--CCITT) without changing data */
unsigned char Index;
unsigned short Crc=0;
while (Count--) {
Index = HBYTE_16(Crc);
HBYTE_16(Crc) = LBYTE_16(Crc);
LBYTE_16(Crc) = *pData++;
Crc = (unsigned short)(Crc ^ NET_CRC_TABLE[Index]);
}
return Crc;
}
I have no idea what the definitions for HByte and LByte are (which is why I didn't post code initially). They are nowhere in the protocool document, so i assumed they were methods in the C library. Basically outside of the table my code is this:
int NET_CRC_Calc(int[] pData, int count) {
int index;
int crc = 0;
for(;count > 0; count--) {
index = crc >> 8;
//TODO: Find out Hbyte method
//LBYTE_16(crc) = pData[count]; ???
crc = (int)(crc ^ NET_CRC_TABLE[index]);
}
return crc;
}
If you would like to test your algorithm before posting (trust i will test anything for you!!), below is the string and expected output.
String command = "<Ver>1</Ver><DtTm></DtTm><Type>3</Type>";
Expected Output: 0x12AA

First of all, make sure you make the NET_CRC_TABLE of type int[]. You can copy the initializer, though.
Next is the pData argument, which is unsigned charin C, and should therefore be a byte array in Java. If you have bytes, make sure that you read unsigned values from the array, by doing
(pData[index] & 0xff)
Then the loop looks like this:
int ptr = 0;
while (count-- > 0) {
index = (crc >> 8) & 0xff;
crc = ((crc & 0xff) << 8) | (pData[ptr++] & 0xff);
crc = crc ^ NET_CRC_TABLE[index];
}
(I have taken liberty to rename the variables to lowercase, as usual in java. Using uppercase variable and method names is frowned upon in the Java world.)
=== EDIT ===
In the case that the whole array must be processed, it makes no sense to pass the count argument at all. Java knows the size of its arrays, unlike C.
So, drop the count parameter and change the loop condition like:
while (ptr < pData.length) {

Based on Ingo's answer, here is a complete solution:
boolean isValidCrc16(int[] crcTable, int crcCode, byte[] toValidate) {
int ptr = 0;
int index;
int computedCrcCode = 0;
boolean isValid;
while (ptr < toValidate.length) {
index = (computedCrcCode >> 8) & 0xff;
computedCrcCode = ((computedCrcCode & 0xff) << 8) | (toValidate[ptr++] & 0xff);
computedCrcCode = computedCrcCode ^ crcTable[index];
}
return computedCrcCode == crcCode;
}