Is there a way I can write one value to a double register using LIBMODBUS? For example writing value 100,000 to be spread across one register. Currently using modbus_write_registers to write 10,000 I am sending the modbus message
rc = modbus_write_registers(ctx, 4, 2, tab_reg); (Where tab_reg[0] = 10,000 and tab_reg[1] = 0)
0A 10 00 04 00 02 04 27 10 00 00 DC 09
Ideally the message i believe I would like to send would not send the 00 00 for the zero value. Is this possible to utilise using Libmodbus?
NB - I have also attempted using modbus_write_register() and this produced a much longer message so I am inclined to believe write registerS is the way to go.
Related
I have a list that is <class 'bytes'> that is comprised of a 16-bit PCM value of <class 'int'>. The list is the result of a direct read of a segment of a 16-bit PCM wave file. I then create a numpy array from that built up list to save it as a separate wave file for training but wavfile.write() always fails because the 16-bit PCM data is wrong somehow, such as:
wavfile.write(savepath + 'wave_speechsegment_' + str(wavecnt) + '.wav', sr, nparray.astype(np.int16)) generates a ValueError: invalid literal for int() with base 10: b'z\xfe' error
And trying nparray directly: wavfile.write(savepath + 'wave_speechsegment_' + str(wavecnt) + '.wav', sr, nparray) I get ValueError: Unsupported data type '|S2
I try to set the list as 16-bit PCM values with:
hexval = struct.pack('<BB', val[0], val[1])
waveform.append(hexval)
nparray = np.array(waveform)
but when I save the 16-bit PCM values to the numpy file, python reports:
nparray is type: <class 'numpy.ndarray'> and nparray[0] is: b'z\xfe' and is type: <class 'numpy.bytes_'>
Saving to the numpy array segment to a file produces precisely the data set found for that segment in the source wave file, such as:
7A FE DE FE C5 FF 75 00 2F 01 76 01 99 01 55 01 05 01 74 00 05 00 9D FF 79 FF 65 FF 8C FF C9 FF
Can someone point me to information about how python deals with data, so that I can keep my 16-bit PCM data as 16-bit PCM data?
In [73]: astr = b'z\xfe'
In [74]: type(astr)
Out[74]: bytes
In [75]: len(astr)
Out[75]: 2 # 2 bytes
This is not a list. It's a string, more specifically a byte string, as opposed to the default (for Python 3) unicode string.
An array, created from such as string, will have a S dtype:
In [76]: arr= np.array(astr)
In [77]: arr
Out[77]: array(b'z\xfe', dtype='|S2')
In [78]: arr= np.array(astr+astr+astr) # + joins strings into one
In [79]: arr
Out[79]: array(b'z\xfez\xfez\xfe', dtype='|S6')
The data-buffer of the array contains those bytes. And can be view as other compatible dtypes.
In [87]: arr= np.array([astr+astr+astr])
In [88]: arr
Out[88]: array([b'z\xfez\xfez\xfe'], dtype='|S6')
In [89]: arr.view('S1')
Out[89]: array([b'z', b'\xfe', b'z', b'\xfe', b'z', b'\xfe'], dtype='|S1')
In [94]: arr.view('int16')
Out[94]: array([-390, -390, -390], dtype=int16)
In [95]: arr.view('uint16')
Out[95]: array([65146, 65146, 65146], dtype=uint16)
In [98]: arr.view('>i2')
Out[98]: array([31486, 31486, 31486], dtype=int16)
I am testing a project. I need to break the payload data(making zero some bytes) of the MPEG-4 ts packets by a percentage coming from the user. I am doing it by reading the ".ts" file packet by packet(188 bytes). But the video is changing to really mud after process. (By the way I'm writing the program in C)
So I decided to find the data/packets that belongs to I-frames, then not touching them but scrambling the other datas by percentage. I could find below
(in hex)
00 00 00 01 E0 start of video PES packet
..
..
00 00 01 B8 start of group of pictures header
..
..
00 00 01 00 the picture start code. This is 32 bits. The 10 bits immediately following this is called as the temporal reference. So temporal reference will include the byte following the picture start code and the first two bits of the second byte after the picture start code ie one byte(8 bits) + 2 bits. These we need to skip. Now the three bits present(3, 4 and 5th bits of the second byte from the picture start code) will indicate the Frame type ie I, B or P. So to get this simply logical AND & the second byte from the picture start code with 0x38 and right shift >> with 3.
For example the data is like that;
00 00 01 00 00 0F FF F8 00 00 01 B5........... and so on.
Here the first four bytes 00 00 01 00 is the picture start code.
The fifth byte and the first two bits of the sixth byte is the temporal reference.
So our concern is in the sixth byte --> 0F
((0F & 38)>>3)
Frame type = 1 ==> I Frame
Frame type 000 forbidden
Frame type 001 intra-coded (I) - iframe
Frame type 010 predictive-coded (P) - p frame
Frame type 011 bidirectionally-predictive-coded (B) - b frame
But this is for MPEG-2. Is there some patterns like that so I recognize and get the frame type with bitwise operations for MPEG-4 transport stream(extension is ".ts")?
And I need to get how many bytes or packets belong to that frame?
Thanks a lot for your help
I would parse the complete TS packet. So first determine what PID your video stream belongs to (by parsing the PAT and PMT). Then find keyframes by looking for the 'Random Access indicator' bit in the Adaptation Field.
uint8_t *pkt = <your 188 byte TS packet>;
assert( 0x47 == pkt[0] );
int16_t pid = ( ( pkt[1] & 0x1F) << 8 ) | pkt[2];
if ( pid == video_pid ) {
// found video stream
if( ( pkt[3] & 0x20 ) && ( pkt[4] > 0 ) ) {
// have AF
if ( pkt[5] & 0x40 ) {
// found keyframe
} } }
If you are using H.264 there should be specific byte stream for I and P frame ..
Like 0x0000000165 for I frame and 0x00000001XX for P frame ..
So just parse and look for continuous such byte stream in such a way you can identify I or P frame..
Again above byte stream is codec implementation dependent ..
For more information you can look into FFMPEG..
I have some Nikon raw files (.nef) which were rendered useless during a USB transfer. However, the size seems fine and only a handful of bits are shifted - by a value of -0x20 (hex) or -32 (dec).
Some of the files could be recovered later with another Computer from the same Card and now I am searching for a solution to recover the other >100 files, which have the same error.
Is there a regular pattern? The offsets seem to be in intervals of 0x800 (2048 in dec).
Differences between the two files
1. /_LXA9414.dump: 13.703.892 bytes
2. /_LXA9414_broken.dump: 13.703.892 bytes
Offsets: hexadec.
84C00: 23 03
13CC00: B1 91
2FA400: 72 52
370400: 25 05
4B9400: AE 8E
641400: 36 16
701400: FC DC
75B400: 27 07
925400: BE 9E
A04C00: A8 88
AC2400: 2F 0F
11 difference(s) found.
Here are more diffs from other files:
http://pastebin.com/9uB3Hx43
F3 c8 42 14 - latitude //05.13637° should be nearby this coordinate
5d a4 40 b2 - longitude //100.47629° should be nearby this coordinate
this is the hex data i get from GPS device, how to convert to readable coordinate?
i don't have any manual document.please help.thanks
22 00 08 00 c3 80 00 20 00 dc f3 c8 42 14 5d a4 40 b2 74 5d 34 4e 52 30 39
47 30 35 31 36 34 00 00 00
this is my full bytes i received,but the engineer told me that F3 c8 42 14 is latitude and 5d a4 40 b2 is longitude
I worked with a Motorola GPS module once and the documentation said that the two hexes represented int types.
In your case, you might want to look at the documentation as well. If you know the model number, you can just google it.
Here is the documentation link for the motorola GPS I used.
Motorola GPS Module
I also took the liberty to do some calculations for you. If your lattitude was indeed
0x1442c8f3
(endianness does make a difference here). The integer equivalent is
339921139
in decimal system. If you divide that by 3600000 milliarcseconds
(where 1 deg = 60 min = 60 * 60 s = 60*60*1000 ms) you get
94.4225386
deg, which is close to your expectations. There isn't enough data to validate it but I believe most of the GPS modules return the milliarcseconds for both latitude and longitude.)
Assuming the hex codes represent unencrypted 32-bit floating point numbers (they might not do), you could try reading them into a C program and printing them out using printf("%f").
Don't forget that the words could have both endianness, i.e. the first one could be F3 C8 42 14 or 14 42 C8 F3 (bytes reversed).
Try it both ways and see if you get anything useful.
I wasn't able to get anything quickly from this online floating point calculator here.
Edit:
Building on Khanal's answer, this link to Latitude/Longitude suggests that the numbers are indeed fixed point and explains the sign convention.
Perhaps more useful for the calculations is HexIt, which allows choosing from a variety of C data types, both integer and floating point, as well as flipping back and forth between little and big endian representations.
I think the values are in 32-bit floating point. However, the bytes are slightly shifted in the stream that you show. Taking longitude first: 100.47629 in 32-bit floating point is 42C8F3DC these are bytes 10 through 13 in your stream (Least significant byte first).
For latitude 5.13637 in 32-bit floating point is 40A45D24 these are bytes 14 through 17 but it's 40A45D14 in the byte stream so it's off a little in the least significant decimal digit (Again, it's least significant byte first).
I am working on a C project in MSVS 2010 (meaning I am using malloc, calloc, and free, not the C++ new and delete operators). I need to find a memory leak(s?), so I've followed the steps on http://msdn.microsoft.com/en-us/library/x98tx3cf.aspx to get the program to dump the memory state at the end of the run.
I include the libraries like so:
#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>
I also specify that every exit should display the debug info like so:
_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
But my debug output looks like this:
Detected memory leaks!
Dumping objects ->
{80181} normal block at 0x016B1D38, 12 bytes long.
Data: < 7 7 8 7 > 0C D5 37 00 14 A9 37 00 38 99 37 00
{80168} normal block at 0x016ACC20, 16 bytes long.
Data: < 7 H 7 X 7 \ 7 > A8 FB 37 00 48 E9 37 00 58 C2 37 00 5C AC 37 00
...
According to the article, I should be getting file name and line number output indicating where the leaked memory is allocated. Why is this not happening, and how can I fix it?
Adrian McCarthy commented that I should ensure that the definition _CRT_MAP_ALLOC existed in every compilation unit. While I could not figure out how to define that as a compiler option, I did create a sparse header file that I ensured every compiled file included. This made the debugging functionality work as expected.