I have a char array that I want to write in the file, but it works only with String objects apparently. What can I do? Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.
Arduino - Data Types
SD Library writing char in a file Ask Question. Asked 4 years, 9 months ago. Active 4 years, 1 month ago. Viewed 1k times. Federico Corazza Federico Corazza 2 2 gold badges 5 5 silver badges 16 16 bronze badges. Active Oldest Votes. You can write char arrays? What makes you think you can't? Depends on the type of string you are talking about.
The strings manipulated by the standard library eg. Try using dataFile. Ashlyn Black Ashlyn Black 8 8 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog.Pages:  2. JO3RI Sr. LCD 16x2 character art posting all my char art here.
Ok So I'll make one topic in which I will show all my Character art. Maybe someone can use a piece. Here goes Thumbs Up Code: [Select]. Re: LCD 16x2 character art posting all my char art here.
And Thumbs Down Code: [Select]. I had seen your code, but Looks great! Can I see a fist flying from the right all the way to the left and hit something? I've been pretty much using the characters and very limited custom characters. Now to think of it, you can make an arrow that rolls around in one character space.
I'll be doing it now and post back!! Mind you, you can only have 8 of those at once on the LCD screen. Didn't someone talk about a rotating arrow? I can't see the video in may last post, or can you only put 4 youtube links in one topic?
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Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. If, as it seems, you are working on an Arduino project, you should simply let the Serial object deal with it:. The other methods can be useful on "normal" machines, but stuff like string and ostringstream require heap allocation, which, on an Arduino board, should be avoided if possible due to the strict memory constraints. I'm leaving it, as it is the correct answer for non-embedded systems.
You can create a formatted string using a stringstreamand extract a string from that. Learn more. Asked 8 years, 4 months ago. Active 8 years, 4 months ago. Viewed 13k times. I need to convert an integer to a string.
Thanks in advance. You must be from a java background.
Arduino - Character Functions
Added tags for Arduino - it makes a big difference here. Fulvio: The fact you're working on an Arduino was an extremely important piece of information you should've added to the question in the first place. For future reference when asking on Stack Overflow, you need to specify which platform you're working on. Insilico Point taken for future reference. Active Oldest Votes. Matteo Italia Matteo Italia k 16 16 gold badges silver badges bronze badges.
You win Matteo, thanks for noticing that it's for an Arduino project. Mike Seymour Mike Seymour k 21 21 gold badges silver badges bronze badges. In that case you'll want one of the other answers. This is a safer option if you've got a full standard library and can afford a bit of memory allocoation.
MikeSeymour Thanks for the answer though, I should've mentioned it was for an Arduino project originally.
Basile Starynkevitch Basile Starynkevitch k 16 16 gold badges silver badges bronze badges. JoeFish JoeFish 2, 14 14 silver badges 23 23 bronze badges. Lalaland Lalaland 7, 3 3 gold badges 27 27 silver badges 45 45 bronze badges. I'm quite sure he doesn't want to use boost on an Arduino board.All data is entered into computers as characters, which includes letters, digits and various special symbols.
The character-handling library includes several functions that perform useful tests and manipulations of character data. Each function receives a character, represented as an int, or EOF as an argument. Characters are often manipulated as integers. Remember that EOF normally has the value —1 and that some hardware architectures do not allow negative values to be stored in char variables.
Therefore, the character-handling functions manipulate characters as integers.
The following table summarizes the functions of the character-handling library. See Appendix D, Number Systems, for a detailed explanation of binary, octal, decimal and hexadecimal numbers. The following example demonstrates the use of the functions isdigit, isalpha, isalnum and isxdigit. Function isdigit determines whether its argument is a digit 0—9. The function isalpha determines whether its argument is an uppercase letter A-Z or a lowercase letter a—z. The function isalnum determines whether its argument is an uppercase, lowercase letter or a digit.
Function isxdigit determines whether its argument is a hexadecimal digit A—F, a—f, 0—9.
We use the conditional operator? For example, line a indicates that if '8' is a digit—i. If '8' is not a digit i. The following example demonstrates the use of the functions islower and isupper. The function islower determines whether its argument is a lowercase letter a—z. Function isupper determines whether its argument is an uppercase letter A—Z.
The following example demonstrates the use of functions isspace, iscntrl, ispunct, isprint and isgraph. The function isprint determines whether its argument is a character that can be displayed on the screen including the space character. The function isgraph tests for the same characters as isprint, but the space character is not included.
Arduino - Character Functions Advertisements. Previous Page. Next Page. Previous Page Print Page.Pages: . Read times previous topic - next topic. I've just been mucking around with the tm libraryand modifying the script for scrolling text the author provides in the documentation. It works, but I'm a bit perplexed by some of it. This is the text that is displayed on the LED array.
To make the text scroll an integer is added to the end. If I look at a serial printout I can see that the string basically is padded with spaces at the end, but I can't work out how adding an int to the end does this. Here's the code: Code: [Select]. Code: [Select]. It is not adding an int to an array, it is adding an offset to the starting address of the array.
Using the array name by itself is a effectively a pointer to the array ie, the address of the 0th element. Ah, ok I get it, thanks. I was thinking it was padding the right hand side of the string, instead it's truncating the left hand side.
Makes sense… mostly. So if pos is the pointer to the array, how does it know how long the array is? Or is it just sending whatever is at sequential memory addresses from pos onwards until it hits an EOL or something? Otherwise why isn't it just returning the contents of the memory past the end of the string? Please do not PM me for help.
I am not a personal consultant. And others will benefit as well if you post your question publicly on the forums.Pages:  2 3. ESP32 Time library, formatting date and writing it to char array. Hello, one thing I am working on right now as part of my still ongoing Arduino trip computer project is converting a given Unix timestamp on the ESP32 into a specific date and time. Does the time library have any functions for that? Here's my code so far, at the moment the time is printed out via serial, when I'm done with it, as I said, I would like to have it all in a char array because I will need that char array to print actual text on my TFT display using my bespoke font libraries.
Code: [Select]. AWOL Guest. Re: ESP32 Time library, formatting date and writing it to char array. Here is how I would do it: Code: [Select]. Here's how my code looks now: Code: [Select]. How many characters in your date string?
How many characters in the buffer you try to put it into? Not sure if your Time. Don't PM me for help as I will ignore it.
Quote from: carguy on Apr 15,pm. Quote from: odometer on Apr 14,pm. What is a null terminator? It's something you need to allow room for. A buffer size of 15 produces correct results.
One minor problem I still have is that I can't enter a Unix timestamp correctly via Serial. When I do, I get back erratic dates that can be anything from Feb 11 to Jan Here's my code again: Code: [Select]. EDIT: I've decided to use a lookup table after all, because the trip computer will come with language settings and it's just more convenient that way. Right now, my code doesn't compile yet.The String library, part of the core as of versionallows you to use and manipulate strings of text in more complex ways than the string character array does.
You can concatenate Strings, append to them, search for and replace substrings, and more. It takes more memory than a simple character array, but it is also more useful. For reference, constant character arrays are referred to as strings with a small s, and String objects are referred to as Strings with a capital S. The default is base ten,so. Or if you prefer binary. Experienced programmers may be wondering how to declare a String of a fixed length of 13 characters.
There's no constructor for that, because Strings can be added to through concatenation, or shortened through using trim. Corrections, suggestions, and new documentation should be posted to the Forum. Code samples in the reference are released into the public domain. Examples All of the following are valid declarations for Strings. The integer will be cast into the character array that represents it. See below for details use a constant integer and a base value. The integer will be cast into a character array that represents in the base.
See below for details. Works the same way as using a constant integer or long integer. You can use other bases, however.
See Also string simple character arrays holding text strings Variable Declaration Reference Home Corrections, suggestions, and new documentation should be posted to the Forum.