20
votes
How to retrieve the data type of a variable?
I use a simple stupid approach...
// serial print variable type
void types(String a) { Serial.println("it's a String"); }
void types(int a) { Serial.println("it's an int"); }
void ...
- 209
20
votes
Can you use Serial Port as a variable?
Majenko's answer is the right answer for your question. But to answer the title of the question, if you ever need to use different Arduino outputs and inputs as variable, most of them have common type ...
- 18.1k
14
votes
Accepted
Can you use Serial Port as a variable?
Yes. The simplest way is with a preprocessor macro. Macros get replaced verbatim before compilation happens, so you can do something like:
#define MY_SERIAL Serial
void setup() {
MY_SERIAL.begin(...
- 105k
13
votes
Accepted
int VS uint8_t VS uint16_t
You can decipher most of them yourself.
A u prefix means unsigned.
The number is the number of bits used. There's 8 bits to the byte.
The _t means it's a typedef.
So a uint8_t is an unsigned 8 bit ...
- 105k
9
votes
Sizeof variables and Due's RAM
sizeof doesn't return the number of elements. It returns the number of bytes. Since they are uint16_t arrays each element is 2 bytes - hence twice the size.
The reason your last number is only 40928 ...
- 105k
9
votes
Accepted
Global or local
No. If you have the choice, locals are usually better, because they
minimize the risk of name collision, and they help make the program
clearer by keeping the variable definition close to the place ...
- 43.9k
8
votes
Accepted
Is there a non-float alternative to pow()?
For the general case, @dat_ha 's answer is correct, but it is worth noting that you want a very special case... powers of two. Because computers use binary arithmetic, operations involving powers of ...
- 206
7
votes
Call by reference
void fcn1(int *variable)
{
fcn2(*variable);
}
This function takes a pointer to an integer as parameter, and then passes the value of the integer to the second function.
To do it by reference, use ...
- 1,320
7
votes
Variable declared inside void setup() is forgotten in void loop()
Yes, that is how C and C++ (and most other C-like languages) work. Variables have "scope". Any variable define inside a pair of curly braces (between a { and a }) is only visible inside those braces.
...
- 5,702
7
votes
Accepted
1 global variable consuming 19% of memory
A few things that count towards the “global variables” that you may not
think of:
all your literal strings, unless encapsulated within the F()
macro; you have quite a few of them
The Serial object, ...
- 43.9k
6
votes
Accepted
Manually Declare Global Variable
You need to research 'Scope'.
Your variable has to be at the same level as all functions that will use it. So at a simple level the answer has to be no.
int variableOne = 0;
void setup ()
{
...
- 5,637
6
votes
Locally declared variable takes up global variable space in dynamic memory/SRAM
Isn't the space taken up by the local variable supposed to be freed up
from the SRAM once the functions runs because I have declared the
variable locally?
This is correct. The local arrays you ...
- 43.9k
6
votes
Accepted
Getting enum name from enum instance
You can print the value as it is:
Serial.println(state);
This will print the the ordering number of the enum, but you can specify the value as any number or char.
enum States
{
SLEEP = 'S',
AWAKE ...
- 18.1k
6
votes
Accepted
How to write nonblocking code, for polling sensor at 100 Hz
should I be declaring last_ms as a global variable instead of
static?
Local static is better, as it limits the scope of the variable to just
where it is needed. Consider making it global only if the ...
- 43.9k
5
votes
How to explain the need/advantage for volatile in terms of microcontroller instruction flow
Short answer: no, volatile cannot be explained in terms of the
figure you show in your question.
Longer answer: there is no direct link between the meaning of volatile
and the architecture depicted ...
- 43.9k
5
votes
Locally declared variable takes up global variable space in dynamic memory/SRAM
You must declare the array in global space or static, and make sure the function you pass the buffer pointer to knows it is in PROGMEM.
void send22()
{
static unsigned int irSignal[] PROGMEM= {...
- 3,267
4
votes
When is it necessary to use "float" instead of "int"?
An integer is a whole or natural number. Computers use integers for counting and comparisons. Computers can count precisely using integers and comparisons of two integers can be absolutely true or ...
- 7,435
4
votes
Accepted
#define VS local static const char
The #define will be substituted in at compile time. So as far as memory usage goes
#define MYSTRING "hello world"
DisplayData(MYSTRING);
and
DisplayData("hello world");
are completely identical.
...
- 1,050
4
votes
Sizeof variables and Due's RAM
The sizeof operator's result is number of bytes, not number of array elements. Your arrays in the program above have two bytes per element, hence twice as many bytes as elements.
If you want to ...
- 8,870
4
votes
Accepted
Arduino - use print(.., DEC) to save into variable
Assuming your code comes from here: https://www.alanzucconi.com/2015/08/19/how-to-hack-any-ir-remote-controller/
Since rawCodes is declared as
unsigned int rawCodes[35];
I.e., it is a 35-element ...
- 3,646
4
votes
Accepted
Assigning array variables to int variables
You really don't need to maintain a list.
Just calculate the LED index from the location:
int room = 14;
int floor = 2;
const int rooms = 92;
int led = room + (floor * rooms);
That is, each floor ...
- 105k
4
votes
Accepted
Make a float using integers
Seems too simple:
float x = n1 + n2 * 0.1;
Is there a trick?
Edit: The method proposed by Michel Keijzers, namely
float x = n1 + n2 / 10.0;
(I removed the redundant casts) can be slightly more ...
- 43.9k
4
votes
Accepted
Wrong use of memory?
As I said in a comment, there is nothing wrong with these declarations.
Now, here are some debugging strategies you may try:
You can rebuild your program with all compiler warnings enabled. Look
...
- 43.9k
3
votes
Accepted
'content' is not captured
Let's look at a simpler example:
void setup ()
{
String content = "Basic";
attachInterrupt (digitalPinToInterrupt (2),
[]()
{
Serial.println(content);
},
FALLING );...
- 38.6k
3
votes
Accepted
Format hour and minute integers to HH:MM format (char*)
You don't want a char *, you want a character array, i.e. you have to
allocate the memory for the string, not only for a pointer. That being
said, you can build the string one character at a time like ...
- 43.9k
3
votes
How to retrieve the data type of a variable?
Building on @snakeNET's answer (which I regard as function overload rather than polymorphism)...
A more generic way would be to pass in a pointer to Print, allowing any Print related class to be used (...
- 155
3
votes
When is it necessary to use "float" instead of "int"?
"int" means integer. It's either one whole number (forgive me, mathematicians, for the sloppy definition!) or the next or previous.
A "float" is a floating-point number - that is, a number and part ...
- 6,974
3
votes
Accepted
How can I set a calculated value when my sketch is uploaded?
The C compilers provide two macros that resolve to string literals: __DATE__ gives the time the file was compiled, and __TIME__ gives the current time of day. They output e.g. "May 31 2017" and "21:...
- 11.3k
Only top scored, non community-wiki answers of a minimum length are eligible