For a while now I've been trying to calculate the checksum for my DFPlayer mini (which will still be delivered). Since I don't have that much experience with the subject, I don't really know how to do it, so I tried to help myself with the data sheet.
Unfortunately, this didn't bring me much and I started to search through forums. And that's when I came across the exact same question that was answered. But I was surprised that in the example in the forum a different checksum came out, than with the data sheet I found. A data sheet was attached to the forum contribution, which contains the same example but with different checksums (see pictures). Example from (my) data sheet ; Example from the data sheet from the forum ; Forum post.
I have already tried to analyze the code of the library which one could use (but I do not want to use it if possible). But since I'm still a beginner, I couldn't rely on my results, partly because the same examples with the different checksums confuse me a lot.
I would be happy if someone could help me here
most of the DFPlayer mini clones use this method:
/*
DFPlayer data frame format:
0 1 2 3 4 5 6 7 8 9-byte
START, VER, LEN, CMD, ACK, DH, DL, SUMH, SUML, END
-------- checksum --------
*/
int16_t checksum = 0;
checksum = checksum - _dataBuffer[1] - _dataBuffer[2] - _dataBuffer[3] - _dataBuffer[4] - _dataBuffer[5] - _dataBuffer[6];
_dataBuffer[7] = checksum >> 8;
_dataBuffer[8] = checksum;
Related
I'm currently trying to tokenize a text file where each line is the body text of a tweet:
"According to data reported to FINRA, short volume percent for $SALT clocked in at 39.19% on 12-29-17 http://www.volumebot.com/?s=SALT"
"#Good2go #krueb The chart I posted definitely supports ng going lower. Gobstopper' 2.12, might even be conservative."
"#Crypt0Fortune Its not dumping as bad as it used to...."
"$XVG.X LOL. Someone just triggered a cascade of stop-loss orders and scooped up morons' coins. Oldest trick in the stock trader's book."
The file is 59,397 lines long (a day's worth of data) and I'm using spaCy for pre-processing/tokenization. It's currently taking me around 8.5 minutes and I was wondering if there were any way of optimising the following code to be quicker as 8.5 minutes seems awfully long for this process:
def token_loop(path):
store = []
files = [f for f in listdir(path) if isfile(join(path, f))]
start_time = time.monotonic()
for filename in files:
with open("./data/"+filename) as f:
for line in f:
tokens = nlp(line.lower())
tokens = [token.lemma_ for token in tokens if not token.orth_.isspace() and token.is_alpha and not token.is_stop and len(token.orth_) != 1]
store.append(tokens)
end_time = time.monotonic()
print("Time taken to tokenize:",timedelta(seconds=end_time - start_time))
return store
Although it says files, it's currently only looping over 1 file.
Just to note, I only need this to tokenize the content; I don't need any extra tagging etc.
It sounds like you haven't optimised the pipeline yet. You'll get a significant speed up from disabling the pipeline components you don't need, like so:
nlp = spacy.load('en', disable=['parser', 'tagger', 'ner'])
This should get you down to about the two-minute mark, or better, on its own.
If you need a further speed up, you can look at multi-threading using nlp.pipe. Docs for multi-threading are here:
https://spacy.io/usage/processing-pipelines#section-multithreading
You can use nlp.pipe(all_lines) instead of nlp(line) for a faster processing
see Spacy's documentation - https://spacy.io/usage/processing-pipelines
Kenneth is a string. Let's say it contains 'justabcsome123texthaha'.
I know this already:
To find text:
if(pos('bcsome12',Kenneth) > 0) then
To check length:
if(Length('Kenneth') > 10) then
Question 1:
I want to find 'texthaha', but only if it is at the end of the string.
if(pos('texthaha',Kenneth) > 0) then
Sadly this will find it anywhere, even if it is in the middle. Is there a simple way?
Question 2:
Is there a simple way to do a search, but with a * (any character in between)?
For example, if I want to search for bcsome1*3text and I don't care what character the * is. I think it's called a wildcard, isn't it?
if(pos('bcsome1'*'3text',Kenneth) > 0) then
I know the above doesn't work. but is there a similar way?
Edit: Might be of importance: **Delphi version used is very old, not sure of the version, but it's from year 2006.
There are functions EndsStr() and EndsText() (the last is case-insensitive) in the StrUtils unit
But, you easily could provide the needed functionality with known functions (Pos also has overloaded version with the third parameter in fresh Delphi):
NPos = Length(S) - Length(Sub) + 1;
if PosEx(Sub, S, NPos) = NPos then...
or variant proposed by #Sertac Akyuz:
if Copy(S, NPos, Length(Sub)) = Sub ...
The second problem might be solved with function like MatchesMask()
if MatchesMask(Kenneth, '*bcsome1*3text*')...
To get the last occurrence, try LastDelimiter (see help). For wildcards, see this post.
This question is based off a previous question I asked concerning a similar topic: Lua: Working with Bit32 Library to Change States of I/O's . I'm trying to use a Lua program that, when a PLC changes the state of a coil at a given address (only two addresses will be used) then it triggers a reaction in another piece of equipment. I have some code that is basically the exact same as my previous topic. But this has to do with what this code is actually doing and not so much the bit32 library. Usually I run code I don't in understand in my Linux IDE and slowly make changes until I finally can make sense of it. But this is producing some weird reactions that I can't make sense of.
Code example:
local unitId = 1
local funcCodes = {
readCoil = 1,
readInput = 2,
readHoldingReg = 3,
readInputReg = 4,
writeCoil = 5,
presetSingleReg = 6,
writeMultipleCoils = 15,
presetMultipleReg = 16
}
local function toTwoByte(value)
return string.char(value / 255, value % 255)
end
local coil = 1
local function readCoil(s, coil)
local req = toTwoByte(0) .. toTwoByte(0) .. toTwoByte(6) .. string.char(unitId, funcCodes.readCoil) .. toTwoByte(coil - 1) .. toTwoByte(1)
s:write(req) --(s is the address of the I/O module)
local res = s:read(10)
return res:byte(10) == 1 -- returns true or false if the 10th bit is ==1 I think??? Please confirm
end
The line that sets local req is the part I'm truly not making sense of. Because of my earlier post, I understand fully about the toTwoByte function and was quickly refreshed on bits & byte manipulation (truly excellent by the way). But that particular string is the reason for this confusion. If I run this in the demo at lua.org I get back an error "lua number has no integer representation". If I separate it into the following I am given back ascii characters that represent those numbers (which I know string.char returns the ascii representation of a given digit). If I run this in my Linux IDE, it displays a bunch of boxes, each containing four digits; two on top of the other two. Now it is very hard to distinguish all of the boxes and their content as they are overlapping.
I know that there is a modbus library that I may be able to use. But I would much rather prefer to understand this as I'm fairly new to programming in general.
Why do I receive different returned results from Windows vs Linux?
What would that string "local req" look like when built at this point to the I/O module. And I don't understand how this req variable translates into the proper string that contains all of the information used to read/write to a given coil or register.
If anyone needs better examples or has further questions that I need to answer, please let me know.
Cheers!
ETA: This is with the Modbus TCP/IP Protocol, not RTU. Sorry.
I'm getting ready to release a tool that is only effective with regular hard drives, not SSD (solid state drive). In fact, it shouldn't be used with SSD's because it will result in a lot of read/writes with no real effectiveness.
Anyone knows of a way of detecting if a given drive is solid-state?
Finally a reliable solution! Two of them, actually!
Check /sys/block/sdX/queue/rotational, where sdX is the drive name. If it's 0, you're dealing with an SSD, and 1 means plain old HDD.
I can't put my finger on the Linux version where it was introduced, but it's present in Ubuntu's Linux 3.2 and in vanilla Linux 3.6 and not present in vanilla 2.6.38. Oracle also backported it to their Unbreakable Enterprise kernel 5.5, which is based on 2.6.32.
There's also an ioctl to check if the drive is rotational since Linux 3.3, introduced by this commit. Using sysfs is usually more convenient, though.
You can actually fairly easily determine the rotational latency -- I did this once as part of a university project. It is described in this report. You'll want to skip to page 7 where you see some nice graphs of the latency. It goes from about 9.3 ms to 1.1 ms -- a drop of 8.2 ms. That corresponds directly to 60 s / 8.2 ms = 7317 RPM.
It was done with simple C code -- here's the part that measures the between positions aand b in a scratch file. We did this with larger and larger b values until we have been wandered all the way around a cylinder:
/* Measure the difference in access time between a and b. The result
* is measured in nanoseconds. */
int measure_latency(off_t a, off_t b) {
cycles_t ta, tb;
overflow_disk_buffer();
lseek(work_file, a, SEEK_SET);
read(work_file, buf, KiB/2);
ta = get_cycles();
lseek(work_file, b, SEEK_SET);
read(work_file, buf, KiB/2);
tb = get_cycles();
int diff = (tb - ta)/cycles_per_ns;
fprintf(stderr, "%i KiB to %i KiB: %i nsec\n", a / KiB, b / KiB, diff);
return diff;
}
This command lsblk -d -o name,rota lists your drives and has a 1 at ROTA if it's a rotational disk and a 0 if it's an SSD.
Example output :
NAME ROTA
sda 1
sdb 0
Detecting SSDs is not as impossible as dseifert makes out. There is already some progress in linux's libata (http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-04/msg03625.html), though it doesn't seem user-ready yet.
And I definitely understand why this needs to be done. It's basically the difference between a linked list and an array. Defragmentation and such is usually counter-productive on a SSD.
You could get lucky by running
smartctl -i sda
from Smartmontools. Almost all SSDs has SSD in the Model field. No guarantee though.
My two cents to answering this old but very important question... If a disk is accessed via SCSI, then you will (potentially) be able to use SCSI INQUIRY command to request its rotational rate. VPD (Vital Product Data) page for that is called Block Device Characteristics and has a number 0xB1. Bytes 4 and 5 of this page contain a number with meaning:
0000h "Medium rotation rate is not reported"
0001h "Non-rotating medium (e.g., solid state)"
0002h - 0400h "Reserved"
0401h - FFFEh "Nominal medium rotation rate in rotations per minute (i.e.,
rpm) (e.g., 7 200 rpm = 1C20h, 10 000 rpm = 2710h, and 15 000 rpm = 3A98h)"
FFFFh "Reserved"
So, SSD must have 0001h in this field. The T10.org document about this page can be found here.
However, the implementation status of this standard is not clear to me.
I wrote the following javascript code. I needed to determine if machine was ussing SSD drive and if it was boot drive. The solution uses MSFT_PhysicalDisk WMI interface.
function main()
{
var retval= false;
// MediaType - 0 Unknown, 3 HDD, 4 SSD
// SpindleSpeed - -1 has rotational speed, 0 has no rotational speed (SSD)
// DeviceID - 0 boot device
var objWMIService = GetObject("winmgmts:\\\\.\\root\\Microsoft\\Windows\\Storage");
var colItems = objWMIService.ExecQuery("select * from MSFT_PhysicalDisk");
var enumItems = new Enumerator(colItems);
for (; !enumItems.atEnd(); enumItems.moveNext())
{
var objItem = enumItems.item();
if (objItem.MediaType == 4 && objItem.SpindleSpeed == 0)
{
if (objItem.DeviceID ==0)
{
retval=true;
}
}
}
if (retval)
{
WScript.Echo("You have SSD Drive and it is your boot drive.");
}
else
{
WScript.Echo("You do not have SSD Drive");
}
return retval;
}
main();
SSD devices emulate a hard disk device interface, so they can just be used like hard disks. This also means that there is no general way to detect what they are.
You probably could use some characteristics of the drive (latency, speed, size), though this won't be accurate for all drives. Another possibility may be to look at the S.M.A.R.T. data and see whether you can determine the type of disk through this (by model name, certain values), however unless you keep a database of all drives out there, this is not gonna be 100% accurate either.
write text file
read text file
repeat 10000 times...
10000/elapsed
for an ssd will be much higher, python3:
def ssd_test():
doc = 'ssd_test.txt'
start = time.time()
for i in range(10000):
with open(doc, 'w+') as f:
f.write('ssd test')
f.close()
with open(doc, 'r') as f:
ret = f.read()
f.close()
stop = time.time()
elapsed = stop - start
ios = int(10000/elapsed)
hd = 'HDD'
if ios > 6000: # ssd>8000; hdd <4000
hd = 'SSD'
print('detecting hard drive type by read/write speed')
print('ios', ios, 'hard drive type', hd)
return hd
I am coding a survey that outputs a .csv file. Within this csv I have some entries that are space delimited, which represent multi-select questions (e.g. questions with more than one response). In the end I want to parse these space delimited entries into their own columns and create headers for them so i know where they came from.
For example I may start with this (note that the multiselect columns have an _M after them):
Q1, Q2_M, Q3, Q4_M
6, 1 2 88, 3, 3 5 99
6, , 3, 1 2
and I want to go to this:
Q1, Q2_M_1, Q2_M_2, Q2_M_88, Q3, Q4_M_1, Q4_M_2, Q4_M_3, Q4_M_5, Q4_M_99
6, 1, 1, 1, 3, 0, 0, 1, 1, 1
6,,,,3,1,1,0,0,0
I imagine this is a relatively common issue to deal with but I have not been able to find it in the R section. Any ideas how to do this in R after importing the .csv ? My general thoughts (which often lead to inefficient programs) are that I can:
(1) pull column numbers that have the special suffix with grep()
(2) loop through (or use an apply) each of the entries in these columns and determine the levels of responses and then create columns accordingly
(3) loop through (or use an apply) and place indicators in appropriate columns to indicate presence of selection
I appreciate any help and please let me know if this is not clear.
I agree with ran2 and aL3Xa that you probably want to change the format of your data to have a different column for each possible reponse. However, if you munging your dataset to a better format proves problematic, it is possible to do what you asked.
process_multichoice <- function(x) lapply(strsplit(x, " "), as.numeric)
q2 <- c("1 2 3 NA 4", "2 5")
processed_q2 <- process_multichoice(q2)
[[1]]
[1] 1 2 3 NA 4
[[2]]
[1] 2 5
The reason different columns for different responses are suggested is because it is still quite unpleasant trying to retrieve any statistics from the data in this form. Although you can do things like
# Number of reponses given
sapply(processed_q2, length)
#Frequency of each response
table(unlist(processed_q2), useNA = "ifany")
EDIT: One more piece of advice. Keep the code that processes your data separate from the code that analyses it. If you create any graphs, keep the code for creating them separate again. I've been down the road of mixing things together, and it isn't pretty. (Especially when you come back to the code six months later.)
I am not entirely sure what you trying to do respectively what your reasons are for coding like this. Thus my advice is more general – so just feel to clarify and I will try to give a more concrete response.
1) I say that you are coding the survey on your own, which is great because it means you have influence on your .csv file. I would NEVER use different kinds of separation in the same .csv file. Just do the naming from the very beginning, just like you suggested in the second block.
Otherwise you might geht into trouble with checkboxes for example. Let's say someone checks 3 out of 5 possible answers, the next only checks 1 (i.e. "don't know") . Now it will be much harder to create a spreadsheet (data.frame) type of results view as opposed to having an empty field (which turns out to be an NA in R) that only needs to be recoded.
2) Another important question is whether you intend to do a panel survey(i.e longitudinal study asking the same participants over and over again) . That (among many others) would be a good reason to think about saving your data to a MySQL database instead of .csv . RMySQL can connect directly to the database and access its tables and more important its VIEWS.
Views really help with survey data since you can rearrange the data in different views, conditional on many different needs.
3) Besides all the personal / opinion and experience, here's some (less biased) literature to get started:
Complex Surveys: A Guide to Analysis Using R (Wiley Series in Survey Methodology
The book is comparatively simple and leaves out panel surveys but gives a lot of R Code and examples which should be a practical start.
To prevent re-inventing the wheel you might want to check LimeSurvey, a pretty decent (not speaking of the templates :) ) tool for survey conductors. Besides I TYPO3 CMS extensions pbsurvey and ke_questionnaire (should) work well too (only tested pbsurvey).
Multiple choice items should always be coded as separate variables. That is, if you have 5 alternatives and multiple choice, you should code them as i1, i2, i3, i4, i5, i.e. each one is a binary variable (0-1). I see that you have values 3 5 99 for Q4_M variable in the first example. Does that mean that you have 99 alternatives in an item? Ouch...
First you should go on and create separate variables for each alternative in a multiple choice item. That is, do:
# note that I follow your example with Q4_M variable
dtf_ins <- as.data.frame(matrix(0, nrow = nrow(<initial dataframe>), ncol = 99))
# name vars appropriately
names(dtf_ins) <- paste("Q4_M_", 1:99, sep = "")
now you have a data.frame with 0s, so what you need to do is to get 1s in an appropriate position (this is a bit cumbersome), a function will do the job...
# first you gotta change spaces to commas and convert character variable to a numeric one
y <- paste("c(", gsub(" ", ", ", x), ")", sep = "")
z <- eval(parse(text = y))
# now you assing 1 according to indexes in z variable
dtf_ins[1, z] <- 1
And that's pretty much it... basically, you would like to reconsider creating a data.frame with _M variables, so you can write a function that does this insertion automatically. Avoid for loops!
Or, even better, create a matrix with logicals, and just do dtf[m] <- 1, where dtf is your multiple-choice data.frame, and m is matrix with logicals.
I would like to help you more on this one, but I'm recuperating after a looong night! =) Hope that I've helped a bit! =)
Thanks for all the responses. I agree with most of you that this format is kind of silly but it is what I have to work with (survey is coded and going into use next week). This is what I came up with from all the responses. I am sure this is not the most elegant or efficient way to do it but I think it should work.
colnums <- grep("_M",colnames(dat))
responses <- nrow(dat)
for (i in colnums) {
vec <- as.vector(dat[,i]) #turn into vector
b <- lapply(strsplit(vec," "),as.numeric) #split up and turn into numeric
c <- sort(unique(unlist(b))) #which values were used
newcolnames <- paste(colnames(dat[i]),"_",c,sep="") #column names
e <- matrix(nrow=responses,ncol=length(c)) #create new matrix for indicators
colnames(e) <- newcolnames
#next loop looks for responses and puts indicators in the correct places
for (i in 1:responses) {
e[i,] <- ifelse(c %in% b[[i]],1,0)
}
dat <- cbind(dat,e)
}
Suggestions for improvement are welcome.